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products/Sources/formale Sprachen/C/Postfix/html/ (Postfix Mailserver Version 3.11^©) Datei vom 2.2.2026 mit Größe 928 kB

Quellcode-Bibliothek postconf.5.html

Sprache: HTML

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<h1><img src="postfix-logo.jpg" width="203" height="98" alt="">Postfix Configuration Parameters </h1>

<hr>

<h2> Postfix main.cf file format </h2>

 The Postfix <a href="postconf.5.html">main.cf</a> configuration file specifies a very small
subset of all the parameters that control the operation of the
Postfix mail system. Parameters not explicitly specified are left
at their default values. 

 The general format of the <a href="postconf.5.html">main.cf</a> file is as follows: 

<ul>

<li> Each logical line is in the form "parameter = value".
Whitespace around the "=" is ignored, as is whitespace at the end
of a logical line. 

<li> Empty lines and whitespace-only lines are ignored, as are
lines whose first non-whitespace character is a `#'. 

<li> A logical line starts with non-whitespace text. A line
that starts with whitespace continues a logical line. 

<li> A parameter value may refer to functions or other parameters. 

<ul>

<li> The expressions "$name" and "${name}" are recursively
replaced with the value of the named parameter. The parameter name
must contain only characters from the set [a-zA-Z0-9_].
An undefined parameter value is replaced with the empty value. 

<li> The expressions "${name?value}" and "${name?{value}}" are
replaced with "value" when "$name" is non-empty. The parameter name
must contain only characters from the set [a-zA-Z0-9_]. These forms are
supported with Postfix versions ≥ 2.2 and ≥ 3.0, respectively.


<li> The expressions "${name:value}" and "${name:{value}}" are
replaced with "value" when "$name" is empty. The parameter name must
contain only characters from the set [a-zA-Z0-9_]. These forms are
supported with Postfix versions ≥ 2.2 and ≥ 3.0, respectively.


<li> The expression "${name?{value1}:{value2}}" is replaced
with "value1" when "$name" is non-empty, and with "value2" when
"$name" is empty. The "{}" is required for "value1", optional for
"value2". The parameter name must contain only characters from the
set [a-zA-Z0-9_]. This form is supported with Postfix versions
≥ 3.0. 

<li> The first item inside "${...}" may be a relational expression
of the form: "{value3} == {value4}". Besides the "==" (equality)
operator Postfix supports "!=" (inequality), "<", "≤", "≥",
and ">". The comparison is numerical when both operands are all
digits, otherwise the comparison is lexicographical. These forms
are supported with Postfix versions ≥ 3.0. 

<li> The expression "${name{value}}" is replaced with the result
from calling the function name with the argument value
after stripping whitespace between the "{", the value, and the "}".
An example is the <a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{} function. 

<li> Each "value" is subject to recursive named parameter and
relational expression evaluation, except where noted. 

<li> Whitespace before or after each "{value}" is ignored. 

<li> Specify "$$" to produce a single "$" character. 

<li> The legacy form "$(...)" is equivalent to the preferred
form "${...}". 

</ul>

<li> When the same parameter is defined multiple times, only
the last instance is remembered. 

<li> Otherwise, the order of <a href="postconf.5.html">main.cf</a> parameter definitions does
not matter. 

</ul>

 The remainder of this document is a description of all Postfix
configuration parameters. Default values are shown after the
parameter name in parentheses, and can be looked up with the
"postconf -d" command. 

 Note: this is not an invitation to make changes to Postfix
configuration parameters. Unnecessary changes are likely to impair
the operation of the mail system. 

<dl>
<DT><a name="2bounce_notice_recipient">2bounce_notice_recipient</a>
(default: postmaster)</DT><DD>

 The recipient of undeliverable mail that cannot be returned to
the sender. This feature is enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a>
parameter. 

</DD>

<DT><a name="access_map_defer_code">access_map_defer_code</a>
(default: 450)</DT><DD>


The numerical Postfix SMTP server response code for
an <a href="access.5.html">access(5)</a> map "defer" action, including "<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>"
or "<a href="postconf.5.html#defer_if_reject">defer_if_reject</a>". Prior to Postfix 2.6, the response
is hard-coded as "450".



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.



This feature is available in Postfix 2.6 and later.


</DD>

<DT><a name="access_map_reject_code">access_map_reject_code</a>
(default: 554)</DT><DD>


The numerical Postfix SMTP server response code for
an <a href="access.5.html">access(5)</a> map "reject" action.



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.


</DD>

<DT><a name="address_verify_cache_cleanup_interval">address_verify_cache_cleanup_interval</a>
(default: 12h)</DT><DD>

 The amount of time between <a href="verify.8.html">verify(8)</a> address verification
database cleanup runs. This feature requires that the database
supports the "delete" and "sequence" operators. Specify a zero
interval to disable database cleanup. 

 After each database cleanup run, the <a href="verify.8.html">verify(8)</a> daemon logs the
number of entries that were retained and dropped. A cleanup run is
logged as "partial" when the daemon terminates early after "postfix
reload", "postfix stop", or no requests for $<a href="postconf.5.html#max_idle">max_idle</a>
seconds. 

 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours). 

 This feature is available in Postfix 2.7. 

</DD>

<DT><a name="address_verify_default_transport">address_verify_default_transport</a>
(default: $<a href="postconf.5.html#default_transport">default_transport</a>)</DT><DD>


Overrides the <a href="postconf.5.html#default_transport">default_transport</a> parameter setting for address
verification probes.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_local_transport">address_verify_local_transport</a>
(default: $<a href="postconf.5.html#local_transport">local_transport</a>)</DT><DD>


Overrides the <a href="postconf.5.html#local_transport">local_transport</a> parameter setting for address
verification probes.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_map">address_verify_map</a>
(default: Postfix ≥ 3.11: $<a href="postconf.5.html#default_cache_db_type">default_cache_db_type</a>:$<a href="postconf.5.html#data_directory">data_directory</a>/verify_cache; Postfix < 3.11: <a href="DATABASE_README.html#types">btree</a>:$<a href="postconf.5.html#data_directory">data_directory</a>/verify_cache)</DT><DD>


Lookup table for persistent address verification status
storage. The table is maintained by the <a href="verify.8.html">verify(8)</a> service, and
is opened before the process releases privileges.



The lookup table is persistent by default (Postfix 2.7 and later).
Specify an empty table name to keep the information in volatile
memory which is lost after "postfix reload" or "postfix
stop". This is the default with Postfix version 2.6 and earlier.



Specify a location in a file system that will not fill up. If the
database becomes corrupted, the world comes to an end. To recover,
delete (NOT: truncate) the file and do "postfix reload".


 Postfix daemon processes do not use root privileges when opening
this file (Postfix 2.5 and later). The file must therefore be
stored under a Postfix-owned directory such as the <a href="postconf.5.html#data_directory">data_directory</a>.
As a migration aid, an attempt to open the file under a non-Postfix
directory is redirected to the Postfix-owned <a href="postconf.5.html#data_directory">data_directory</a>, and a
warning is logged. 


Examples:


<pre>
<a href="postconf.5.html#address_verify_map">address_verify_map</a> = $<a href="postconf.5.html#default_cache_db_type">default_cache_db_type</a>:$<a href="postconf.5.html#data_directory">data_directory</a>/verify_cache
<a href="postconf.5.html#address_verify_map">address_verify_map</a> = <a href="lmdb_table.5.html">lmdb</a>:/var/lib/postfix/verify_cache
<a href="postconf.5.html#address_verify_map">address_verify_map</a> = <a href="DATABASE_README.html#types">btree</a>:/var/lib/postfix/verify_cache
</pre>


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_negative_cache">address_verify_negative_cache</a>
(default: yes)</DT><DD>


Enable caching of failed address verification probe results. When
this feature is enabled, the cache may pollute quickly with garbage.
When this feature is disabled, Postfix will generate an address
probe for every lookup.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_negative_expire_time">address_verify_negative_expire_time</a>
(default: 3d)</DT><DD>


The time after which a failed probe expires from the address
verification cache.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_negative_refresh_time">address_verify_negative_refresh_time</a>
(default: 3h)</DT><DD>


The time after which a failed address verification probe needs to
be refreshed.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_pending_request_limit">address_verify_pending_request_limit</a>
(default: see "postconf -d" output)</DT><DD>

 A safety limit that prevents address verification requests from
overwhelming the Postfix queue. By default, the number of pending
requests is limited to 1/4 of the <a href="QSHAPE_README.html#active_queue">active queue</a> maximum size
(<a href="postconf.5.html#qmgr_message_active_limit">qmgr_message_active_limit</a>). The queue manager enforces the limit
by tempfailing requests that exceed the limit. This affects only
unknown addresses and inactive addresses that have expired, because
the <a href="verify.8.html">verify(8)</a> daemon automatically refreshes an active address
before it expires. 

 This feature is available in Postfix 3.1 and later. 

</DD>

<DT><a name="address_verify_poll_count">address_verify_poll_count</a>
(default: normal: 3, <a href="STRESS_README.html">overload</a>: 1)</DT><DD>


How many times to query the <a href="verify.8.html">verify(8)</a> service for the completion
of an address verification request in progress.


 By default, the Postfix SMTP server polls the <a href="verify.8.html">verify(8)</a> service
up to three times under non-overload conditions, and only once when
under overload. With Postfix version 2.5 and earlier, the SMTP
server always polls the <a href="verify.8.html">verify(8)</a> service up to three times by
default. 


Specify 1 to implement a crude form of greylisting, that is, always
defer the first delivery request for a new address.



Examples:


<pre>
# Postfix ≤ 2.6 default
<a href="postconf.5.html#address_verify_poll_count">address_verify_poll_count</a> = 3
# Poor man's greylisting
<a href="postconf.5.html#address_verify_poll_count">address_verify_poll_count</a> = 1
</pre>


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_poll_delay">address_verify_poll_delay</a>
(default: 3s)</DT><DD>


The delay between queries for the completion of an address
verification request in progress.



The default polling delay is 3 seconds.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_positive_expire_time">address_verify_positive_expire_time</a>
(default: 31d)</DT><DD>


The time after which a successful probe expires from the address
verification cache.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_positive_refresh_time">address_verify_positive_refresh_time</a>
(default: 7d)</DT><DD>


The time after which a successful address verification probe needs
to be refreshed. The address verification status is not updated
when the probe fails (optimistic caching).


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_relay_transport">address_verify_relay_transport</a>
(default: $<a href="postconf.5.html#relay_transport">relay_transport</a>)</DT><DD>


Overrides the <a href="postconf.5.html#relay_transport">relay_transport</a> parameter setting for address
verification probes.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_relayhost">address_verify_relayhost</a>
(default: $<a href="postconf.5.html#relayhost">relayhost</a>)</DT><DD>


Overrides the <a href="postconf.5.html#relayhost">relayhost</a> parameter setting for address verification
probes. This information can be overruled with the <a href="transport.5.html">transport(5)</a> table.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_sender">address_verify_sender</a>
(default: $<a href="postconf.5.html#double_bounce_sender">double_bounce_sender</a>)</DT><DD>

 The sender address to use in address verification probes; prior
to Postfix 2.5 the default was "postmaster". To
avoid problems with address probes that are sent in response to
address probes, the Postfix SMTP server excludes the probe sender
address from all SMTPD access blocks. 


Specify an empty value (<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> =) or <> if you want
to use the null sender address. Beware, some sites reject mail from
<>, even though RFCs require that such addresses be accepted.



Examples:


<pre>
<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> = <>
<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> = postmaster@<a href="postconf.5.html#mydomain">mydomain</a>
</pre>


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_sender_dependent_default_transport_maps">address_verify_sender_dependent_default_transport_maps</a>
(default: $<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a>)</DT><DD>

 Overrides the <a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> parameter
setting for address verification probes. 

 This feature is available in Postfix 2.7 and later. 

</DD>

<DT><a name="address_verify_sender_dependent_relayhost_maps">address_verify_sender_dependent_relayhost_maps</a>
(default: $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>)</DT><DD>


Overrides the <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> parameter setting for address
verification probes.



This feature is available in Postfix 2.3 and later.


</DD>

<DT><a name="address_verify_sender_ttl">address_verify_sender_ttl</a>
(default: 0s)</DT><DD>

 The time between changes in the time-dependent portion of address
verification probe sender addresses. The time-dependent portion is
appended to the localpart of the address specified with the
<a href="postconf.5.html#address_verify_sender">address_verify_sender</a> parameter. This feature is ignored when the
probe sender addresses is the null sender, i.e. the <a href="postconf.5.html#address_verify_sender">address_verify_sender</a>
value is empty or <>. 

 Historically, the probe sender address was fixed. This has
caused such addresses to end up on spammer mailing lists, and has
resulted in wasted network and processing resources. 

 To enable time-dependent probe sender addresses, specify a
non-zero time value. Specify a value of at least several hours,
to avoid problems with senders that use greylisting. Avoid nice
TTL values, to make the result less predictable. 

 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.9 and later. 

</DD>

<DT><a name="address_verify_service_name">address_verify_service_name</a>
(default: verify)</DT><DD>


The name of the <a href="verify.8.html">verify(8)</a> address verification service. This service
maintains the status of sender and/or recipient address verification
probes, and generates probes on request by other Postfix processes.


</DD>

<DT><a name="address_verify_transport_maps">address_verify_transport_maps</a>
(default: $<a href="postconf.5.html#transport_maps">transport_maps</a>)</DT><DD>


Overrides the <a href="postconf.5.html#transport_maps">transport_maps</a> parameter setting for address verification
probes.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="address_verify_virtual_transport">address_verify_virtual_transport</a>
(default: $<a href="postconf.5.html#virtual_transport">virtual_transport</a>)</DT><DD>


Overrides the <a href="postconf.5.html#virtual_transport">virtual_transport</a> parameter setting for address
verification probes.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="alias_database">alias_database</a>
(default: see "postconf -d" output)</DT><DD>


The alias databases for <a href="local.8.html">local(8)</a> delivery that are updated with
"newaliases" or with "sendmail -bi".



This is a separate configuration parameter because not all the
tables specified with $<a href="postconf.5.html#alias_maps">alias_maps</a> have to be local files.



Examples:


<pre>
<a href="postconf.5.html#alias_database">alias_database</a> = $<a href="postconf.5.html#default_database_type">default_database_type</a>:/etc/aliases
<a href="postconf.5.html#alias_database">alias_database</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/aliases
<a href="postconf.5.html#alias_database">alias_database</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/mail/aliases
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

</DD>

<DT><a name="alias_maps">alias_maps</a>
(default: see "postconf -d" output)</DT><DD>


Optional lookup tables that are searched only with an email address
localpart (no domain) and that apply only to <a href="local.8.html">local(8)</a> recipients;
this is unlike <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> that are often searched with a
full email address (including domain) and that apply to all recipients:
<a href="local.8.html">local(8)</a>, virtual, and remote.
The <a href="postconf.5.html#alias_maps">alias_maps</a> table format and lookups are documented in <a href="aliases.5.html">aliases(5)</a>.
For an overview of Postfix address manipulations see the
<a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> document. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.
Note: these lookups are recursive.



The default list is system dependent. On systems with NIS, the
default is to search the local alias database, then the NIS alias
database.



The <a href="local.8.html">local(8)</a> delivery agent disallows regular expression substitution
of $1 etc. in <a href="postconf.5.html#alias_maps">alias_maps</a>, because that would open a security hole.



The <a href="local.8.html">local(8)</a> delivery agent will silently ignore requests to use
the <a href="proxymap.8.html">proxymap(8)</a> server within <a href="postconf.5.html#alias_maps">alias_maps</a>. Instead it will open the
table directly. Before Postfix version 2.2, the <a href="local.8.html">local(8)</a> delivery
agent will terminate with a fatal error.



Examples:


<pre>
<a href="postconf.5.html#alias_maps">alias_maps</a> = $<a href="postconf.5.html#default_database_type">default_database_type</a>:/etc/aliases, nis:mail.aliases
<a href="postconf.5.html#alias_maps">alias_maps</a> = $<a href="postconf.5.html#default_database_type">default_database_type</a>:/etc/aliases
<a href="postconf.5.html#alias_maps">alias_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/mail/aliases
<a href="postconf.5.html#alias_maps">alias_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/aliases
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postalias /path/to/aliases" after you
change the aliases file, to (re)build a default-type indexed file.
Execute "postalias type:/path/to/aliases" to specify an explicit
type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

</DD>

<DT><a name="allow_mail_to_commands">allow_mail_to_commands</a>
(default: alias, forward)</DT><DD>


Restrict <a href="local.8.html">local(8)</a> mail delivery to external commands. The default
is to disallow delivery to "|command" in :include: files (see
<a href="aliases.5.html">aliases(5)</a> for the text that defines this terminology).



Specify zero or more of: alias, forward or include,
in order to allow commands in <a href="aliases.5.html">aliases(5)</a>, .forward files or in
:include: files, respectively.



Example:


<pre>
<a href="postconf.5.html#allow_mail_to_commands">allow_mail_to_commands</a> = alias,forward,include
</pre>

</DD>

<DT><a name="allow_mail_to_files">allow_mail_to_files</a>
(default: alias, forward)</DT><DD>


Restrict <a href="local.8.html">local(8)</a> mail delivery to external files. The default is
to disallow "/file/name" destinations in :include: files (see
<a href="aliases.5.html">aliases(5)</a> for the text that defines this terminology).



Specify zero or more of: alias, forward or include,
in order to allow "/file/name" destinations in <a href="aliases.5.html">aliases(5)</a>, .forward
files and in :include: files, respectively.



Example:


<pre>
<a href="postconf.5.html#allow_mail_to_files">allow_mail_to_files</a> = alias,forward,include
</pre>

</DD>

<DT><a name="allow_min_user">allow_min_user</a>
(default: no)</DT><DD>


Allow a sender or recipient address to have `-' as the first
character. By
default, this is not allowed, to avoid accidents with software that
passes email addresses via the command line. Such software
would not be able to distinguish a malicious address from a
bona fide command-line option. Although this can be prevented by
inserting a "--" option terminator into the command line, this is
difficult to enforce consistently and globally. 

 As of Postfix version 2.5, this feature is implemented by
<a href="trivial-rewrite.8.html">trivial-rewrite(8)</a>. With earlier versions this feature was implemented
by <a href="qmgr.8.html">qmgr(8)</a> and was limited to recipient addresses only. 

</DD>

<DT><a name="allow_percent_hack">allow_percent_hack</a>
(default: yes)</DT><DD>


Enable the rewriting of the form "user%domain" to "user@domain".
This is enabled by default.


 Note: as of Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true: 

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

 To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". 


Example:


<pre>
<a href="postconf.5.html#allow_percent_hack">allow_percent_hack</a> = no
</pre>

</DD>

<DT><a name="allow_srv_lookup_fallback">allow_srv_lookup_fallback</a>
(default: no)</DT><DD>

 When SRV record lookup fails or no SRV record exists, fall back
to MX or IP address lookup as if SRV record lookup was not enabled. 

 This feature is available in Postfix 3.8 and later. 

</DD>

<DT><a name="allow_untrusted_routing">allow_untrusted_routing</a>
(default: no)</DT><DD>


Forward mail with sender-specified routing (user[@%!]remote[@%!]site)
from untrusted clients to destinations matching $<a href="postconf.5.html#relay_domains">relay_domains</a>.



By default, this feature is turned off. This closes a nasty open
relay loophole where a backup MX host can be tricked into forwarding
junk mail to a primary MX host which then spams it out to the world.



This parameter also controls if non-local addresses with sender-specified
routing can match Postfix access tables. By default, such addresses
cannot match Postfix access tables, because the address is ambiguous.


</DD>

<DT><a name="alternate_config_directories">alternate_config_directories</a>
(default: empty)</DT><DD>


A list of non-default Postfix configuration directories that may
be specified with "-c <a href="postconf.5.html#config_directory">config_directory</a>" on the command line (in the
case of <a href="sendmail.1.html">sendmail(1)</a>, with the "-C" option), or via the MAIL_CONFIG
environment parameter.



This list must be specified in the default Postfix <a href="postconf.5.html">main.cf</a> file,
and will be used by set-gid Postfix commands such as <a href="postqueue.1.html">postqueue(1)</a>
and <a href="postdrop.1.html">postdrop(1)</a>.



Specify absolute pathnames, separated by comma or space. Note: $name
expansion is not supported.


</DD>

<DT><a name="always_add_missing_headers">always_add_missing_headers</a>
(default: no)</DT><DD>

 Always add (Resent-) From:, To:, Date: or Message-ID: headers
when not present. Postfix 2.6 and later add these headers only
when clients match the <a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> parameter
setting. Earlier Postfix versions always add these headers; this
may break DKIM signatures that cover non-existent headers.
The <a href="postconf.5.html#undisclosed_recipients_header">undisclosed_recipients_header</a> parameter setting determines
whether a To: header will be added. 

</DD>

<DT><a name="always_bcc">always_bcc</a>
(default: empty)</DT><DD>


Optional address that receives a "blind carbon copy" of each message
that is received by the Postfix mail system.



Note: with Postfix 2.3 and later the BCC address is added as if it
was specified with NOTIFY=NONE. The sender will not be notified
when the BCC address is undeliverable, as long as all down-stream
software implements <a href="https://tools.ietf.org/html/rfc3461">RFC 3461</a>.



Note: with Postfix 2.2 and earlier the sender will be notified
when the BCC address is undeliverable.


 Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
after Postfix forwards mail internally, or after Postfix generates
mail itself. 

 Note: automatic BCC recipients are subject to address
canonicalization (add missing domain), <a href="postconf.5.html#canonical_maps">canonical_maps</a>, <a href="postconf.5.html#masquerade_domains">masquerade_domains</a>,
and <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>. 

</DD>

<DT><a name="anvil_rate_time_unit">anvil_rate_time_unit</a>
(default: 60s)</DT><DD>


The time unit over which client connection rates and other rates
are calculated.



This feature is implemented by the <a href="anvil.8.html">anvil(8)</a> service which is available
in Postfix version 2.2 and later.



The default interval is relatively short. Because of the high
frequency of updates, the <a href="anvil.8.html">anvil(8)</a> server uses volatile memory
only. Thus, information is lost whenever the process terminates.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="anvil_status_update_time">anvil_status_update_time</a>
(default: 600s)</DT><DD>


How frequently the <a href="anvil.8.html">anvil(8)</a> connection and rate limiting server
logs peak usage information.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


This feature is available in Postfix 2.2 and later.


</DD>

<DT><a name="append_at_myorigin">append_at_myorigin</a>
(default: yes)</DT><DD>


With locally submitted mail, append the string "@$<a href="postconf.5.html#myorigin">myorigin</a>" to mail
addresses without domain information. With remotely submitted mail,
append the string "@$<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>" instead.



Note 1: this feature is enabled by default and must not be turned off.
Postfix does not support domain-less addresses.


 Note 2: with Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true: 

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

 To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". 

</DD>

<DT><a name="append_dot_mydomain">append_dot_mydomain</a>
(default: Postfix ≥ 3.0: no, Postfix < 3.0: yes)</DT><DD>


With locally submitted mail, append the string ".$<a href="postconf.5.html#mydomain">mydomain</a>" to
addresses that have no ".domain" information. With remotely submitted
mail, append the string ".$<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a>"
instead.



Note 1: When disabled (Postfix 3.0 and later), users will not be
able to send mail to "user@partialdomainname" but will have to
specify full domain names instead.


 Note 2: with Postfix version 2.2, message header address rewriting
happens only when one of the following conditions is true: 

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

 To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". 

</DD>

<DT><a name="application_event_drain_time">application_event_drain_time</a>
(default: 100s)</DT><DD>


How long the <a href="postkick.1.html">postkick(1)</a> command waits for a request to enter the
Postfix daemon process input buffer before giving up.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="authorized_flush_users">authorized_flush_users</a>
(default: <a href="DATABASE_README.html#types">static</a>:anyone)</DT><DD>


List of users who are authorized to flush the queue.



By default, all users are allowed to flush the queue. Access is
always granted if the invoking user is the super-user or the
$<a href="postconf.5.html#mail_owner">mail_owner</a> user. Otherwise, the real UID of the process is looked
up in the system password file, and access is granted only if the
corresponding login name is on the access list. The username
"unknown" is used for processes whose real UID is not found in the
password file. 


Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A "/file/name"
pattern is replaced
by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
matches a lookup key (the lookup result is ignored). Continue long
lines by starting the next line with whitespace. Specify "!pattern"
to exclude a name from the list. The form "!/file/name" is supported
only in Postfix version 2.4 and later. 


This feature is available in Postfix 2.2 and later.


</DD>

<DT><a name="authorized_mailq_users">authorized_mailq_users</a>
(default: <a href="DATABASE_README.html#types">static</a>:anyone)</DT><DD>


List of users who are authorized to view the queue.



By default, all users are allowed to view the queue. Access is
always granted if the invoking user is the super-user or the
$<a href="postconf.5.html#mail_owner">mail_owner</a> user. Otherwise, the real UID of the process is looked
up in the system password file, and access is granted only if the
corresponding login name is on the access list. The username
"unknown" is used for processes whose real UID is not found in the
password file. 


Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A "/file/name"
pattern is replaced
by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
matches a lookup key (the lookup result is ignored). Continue long
lines by starting the next line with whitespace. Specify "!pattern"
to exclude a user name from the list. The form "!/file/name" is
supported only in Postfix version 2.4 and later. 


This feature is available in Postfix 2.2 and later.


</DD>

<DT><a name="authorized_submit_users">authorized_submit_users</a>
(default: <a href="DATABASE_README.html#types">static</a>:anyone)</DT><DD>


List of users who are authorized to submit mail with the <a href="sendmail.1.html">sendmail(1)</a>
command (and with the privileged <a href="postdrop.1.html">postdrop(1)</a> helper command).



By default, all users are allowed to submit mail. Otherwise, the
real UID of the process is looked up in the system password file,
and access is granted only if the corresponding login name is on
the access list. The username "unknown" is used for processes
whose real UID is not found in the password file. To deny mail
submission access to all users specify an empty list. 


Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to right,
and the search stops on the first match. A "/file/name" pattern is
replaced by its contents;
a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name matches a lookup key
(the lookup result is ignored). Continue long lines by starting the
next line with whitespace. Specify "!pattern" to exclude a user
name from the list. The form "!/file/name" is supported only in
Postfix version 2.4 and later. 


Example:


<pre>
<a href="postconf.5.html#authorized_submit_users">authorized_submit_users</a> = !www, <a href="DATABASE_README.html#types">static</a>:all
</pre>


This feature is available in Postfix 2.2 and later.


</DD>

<DT><a name="authorized_verp_clients">authorized_verp_clients</a>
(default: $<a href="postconf.5.html#mynetworks">mynetworks</a>)</DT><DD>

 What remote SMTP clients are allowed to specify the XVERP command.
This command requests that mail be delivered one recipient at a
time with a per recipient return address. 

 By default, only trusted clients are allowed to specify XVERP.


 This parameter was introduced with Postfix version 1.1. Postfix
version 2.1 renamed this parameter to <a href="postconf.5.html#smtpd_authorized_verp_clients">smtpd_authorized_verp_clients</a>
and changed the default to none. 

 Specify a list of network/netmask patterns, separated by commas
and/or whitespace. The mask specifies the number of bits in the
network part of a host address. You can also specify hostnames or
.domain names (the initial dot causes the domain to match any name
below it), "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns. A "/file/name"
pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
is matched when a table entry matches a lookup string (the lookup
result is ignored). Continue long lines by starting the next line
with whitespace. Specify "!pattern" to exclude an address or network
block from the list. The form "!/file/name" is supported only in
Postfix version 2.4 and later. 

 Note: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#authorized_verp_clients">authorized_verp_clients</a> value, and in files
specified with "/file/name". IP version 6 addresses contain the
":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
pattern. 

</DD>

<DT><a name="backwards_bounce_logfile_compatibility">backwards_bounce_logfile_compatibility</a>
(default: yes)</DT><DD>


Produce additional <a href="bounce.8.html">bounce(8)</a> logfile records that can be read by
Postfix versions before 2.0. The current and more extensible "name =
value" format is needed in order to implement more sophisticated
functionality.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="berkeley_db_create_buffer_size">berkeley_db_create_buffer_size</a>
(default: 16777216)</DT><DD>


The per-table I/O buffer size for programs that create Berkeley DB
hash or btree tables. Specify a byte count.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="berkeley_db_read_buffer_size">berkeley_db_read_buffer_size</a>
(default: 131072)</DT><DD>


The per-table I/O buffer size for programs that read Berkeley DB
hash or btree tables. Specify a byte count.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="best_mx_transport">best_mx_transport</a>
(default: empty)</DT><DD>


Where the Postfix SMTP client should deliver mail when it detects
a "mail loops back to myself" error condition. This happens when
the local MTA is the best SMTP mail exchanger for a destination
not listed in $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>, $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>,
$<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, or $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>. By default,
the Postfix SMTP client returns such mail as undeliverable.



Specify, for example, "<a href="postconf.5.html#best_mx_transport">best_mx_transport</a> = local" to pass the mail
from the Postfix SMTP client to the <a href="local.8.html">local(8)</a> delivery agent. You
can specify
any message delivery "transport" or "transport:nexthop" that is
defined in the <a href="master.5.html">master.cf</a> file. See the <a href="transport.5.html">transport(5)</a> manual page
for the syntax and meaning of "transport" or "transport:nexthop".



However, this feature is expensive because it ties up a Postfix
SMTP client process while the <a href="local.8.html">local(8)</a> delivery agent is doing its
work. It is more efficient (for Postfix) to list all <a href="VIRTUAL_README.html#canonical">hosted domains</a>
in a table or database.


</DD>

<DT><a name="biff">biff</a>
(default: yes)</DT><DD>


Whether or not to use the local <a href="postconf.5.html#biff">biff</a> service. This service sends
"new mail" notifications to users who have requested new mail
notification with the UNIX command "<a href="postconf.5.html#biff">biff</a> y".



For compatibility reasons this feature is on by default. On systems
with lots of interactive users, the <a href="postconf.5.html#biff">biff</a> service can be a performance
drain. Specify "<a href="postconf.5.html#biff">biff</a> = no" in <a href="postconf.5.html">main.cf</a> to disable.


</DD>

<DT><a name="body_checks">body_checks</a>
(default: empty)</DT><DD>

 Optional lookup tables for content inspection as specified in
the <a href="header_checks.5.html">body_checks(5)</a> manual page. 

 Note: with Postfix versions before 2.0, these rules inspect
all content after the primary message headers. 

</DD>

<DT><a name="body_checks_size_limit">body_checks_size_limit</a>
(default: 51200)</DT><DD>


How much text in a message body segment (or attachment, if you
prefer to use that term) is subjected to <a href="postconf.5.html#body_checks">body_checks</a> inspection.
The amount of text is limited to avoid scanning huge attachments.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="bounce_notice_recipient">bounce_notice_recipient</a>
(default: postmaster)</DT><DD>


The recipient of postmaster notifications with the message headers
of mail that Postfix did not deliver and of SMTP conversation
transcripts of mail that Postfix did not receive. This feature is
enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a> parameter. 

</DD>

<DT><a name="bounce_queue_lifetime">bounce_queue_lifetime</a>
(default: 5d)</DT><DD>


Consider a bounce message as undeliverable, when delivery fails
with a temporary error, and the time in the queue has reached the
<a href="postconf.5.html#bounce_queue_lifetime">bounce_queue_lifetime</a> limit. By default, this limit is the same
as for regular mail.


 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 


Specify 0 when mail delivery should be tried only once.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="bounce_service_name">bounce_service_name</a>
(default: bounce)</DT><DD>


The name of the <a href="bounce.8.html">bounce(8)</a> service. This service maintains a record
of failed delivery attempts and generates non-delivery notifications.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="bounce_size_limit">bounce_size_limit</a>
(default: 50000)</DT><DD>

 The maximal amount of original message text that is sent in a
non-delivery notification. Specify a byte count. A message is
returned as either message/rfc822 (the complete original) or as
text/rfc822-headers (the headers only). With Postfix version 2.4
and earlier, a message is always returned as message/rfc822 and is
truncated when it exceeds the size limit.


 Notes: 

<ul>

<li> If you increase this limit, then you should increase the
<a href="postconf.5.html#mime_nesting_limit">mime_nesting_limit</a> value proportionally. 

<li> Be careful when making changes. Excessively large values
will result in the loss of non-delivery notifications, when a bounce
message size exceeds a local or remote MTA's message size limit.


</ul>

</DD>

<DT><a name="bounce_template_file">bounce_template_file</a>
(default: empty)</DT><DD>

 Pathname of a configuration file with bounce message templates.
These override the built-in templates of delivery status notification
(DSN) messages for undeliverable mail, delayed mail, successful
delivery, or delivery verification. The <a href="bounce.5.html">bounce(5)</a> manual page
describes how to edit and test template files. 

 Template message body text may contain $name references to
Postfix configuration parameters. The result of $name expansion can
be previewed with "postconf -b file_name" before the file
is placed into the Postfix configuration directory. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="broken_sasl_auth_clients">broken_sasl_auth_clients</a>
(default: no)</DT><DD>


Enable interoperability with remote SMTP clients that implement an obsolete
version of the AUTH command (<a href="https://tools.ietf.org/html/rfc4954">RFC 4954</a>). Examples of such clients
are MicroSoft Outlook Express version 4 and MicroSoft Exchange
version 5.0.



Specify "<a href="postconf.5.html#broken_sasl_auth_clients">broken_sasl_auth_clients</a> = yes" to have Postfix advertise
AUTH support in a non-standard way.


</DD>

<DT><a name="canonical_classes">canonical_classes</a>
(default: envelope_sender, envelope_recipient, header_sender, header_recipient)</DT><DD>

 What addresses are subject to <a href="postconf.5.html#canonical_maps">canonical_maps</a> address mapping.
By default, <a href="postconf.5.html#canonical_maps">canonical_maps</a> address mapping is applied to envelope
sender and recipient addresses, and to header sender and header
recipient addresses. 

 Specify one or more of: envelope_sender, envelope_recipient,
header_sender, header_recipient 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="canonical_maps">canonical_maps</a>
(default: empty)</DT><DD>


Optional address mapping lookup tables for message headers and
envelopes. The mapping is applied to both sender and recipient
addresses, in both envelopes and in headers, as controlled
with the <a href="postconf.5.html#canonical_classes">canonical_classes</a> parameter. This is typically used
to clean up dirty addresses from legacy mail systems, or to replace
login names by Firstname.Lastname. The table format and lookups
are documented in <a href="canonical.5.html">canonical(5)</a>. For an overview of Postfix address
manipulations see the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> document.



Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.
Note: these lookups are recursive.


 Note: with Postfix version 2.2, message header address mapping
happens only when message header address rewriting is enabled: 

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

 To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". 


Examples:


<pre>
<a href="postconf.5.html#canonical_maps">canonical_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/canonical
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/canonical" after you
change the canonical file, to (re)build a default-type indexed file.
Execute "postmap type:/etc/postfix/canonical" to specify an
explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

</DD>

<DT><a name="cleanup_replace_stray_cr_lf">cleanup_replace_stray_cr_lf</a>
(default: yes)</DT><DD>

 Replace each stray <CR> or <LF> character in message
content with a space character, to prevent outbound SMTP smuggling,
and to make the evaluation of Postfix-added DKIM or other signatures
independent from how a remote mail server handles such characters.


 SMTP does not allow such characters unless they are part of a
<CR><LF> sequence, and different mail systems handle
such stray characters in an implementation-dependent manner. Stray
<CR> or <LF> characters could be used for outbound
SMTP smuggling, where an attacker uses a Postfix server to send
message content with a non-standard End-of-DATA sequence that
triggers inbound SMTP smuggling at a remote SMTP server.

 The replacement happens before all other content management,
and before Postfix may add a DKIM etc. signature; if the signature
were created first, the replacement could invalidate the signature.


 In addition to preventing SMTP smuggling, replacing stray
<CR> or <LF> characters ensures that the result of
signature validation by later mail system will not depend on how
that mail system handles those stray characters in an
implementation-dependent manner. 

 Note: this feature is disabled with "<a href="postconf.5.html#receive_override_options">receive_override_options</a> =
<a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>". 

 This feature is available in Postfix ≥ 3.9, 3.8.5, 3.7.10,
3.6.14, and 3.5.24. 

</DD>

<DT><a name="cleanup_service_name">cleanup_service_name</a>
(default: cleanup)</DT><DD>


The name of the <a href="cleanup.8.html">cleanup(8)</a> service. This service rewrites addresses
into the standard form, and performs <a href="canonical.5.html">canonical(5)</a> address mapping
and <a href="virtual.5.html">virtual(5)</a> aliasing.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="command_directory">command_directory</a>
(default: see "postconf -d" output)</DT><DD>


The location of all postfix administrative commands.


</DD>

<DT><a name="command_execution_directory">command_execution_directory</a>
(default: empty)</DT><DD>

 The <a href="local.8.html">local(8)</a> delivery agent working directory for delivery to
external commands. Failure to change directory causes the delivery
to be deferred. 

 The <a href="postconf.5.html#command_execution_directory">command_execution_directory</a> value is not subject to Postfix
configuration parameter $name expansion. Instead, the following
$name expansions are done on <a href="postconf.5.html#command_execution_directory">command_execution_directory</a> before the
directory is used. Expansion happens in the context
of the delivery request. The result of $name expansion is filtered
with the character set that is specified with the
<a href="postconf.5.html#execution_directory_expansion_filter">execution_directory_expansion_filter</a> parameter. 

<dl>

<dt>$user</dt>

<dd>The recipient's username. </dd>

<dt>$shell</dt>

<dd>The recipient's login shell pathname. </dd>

<dt>$home</dt>

<dd>The recipient's home directory. </dd>

<dt>$recipient</dt>

<dd>The full recipient address. </dd>

<dt>$extension</dt>

<dd>The optional recipient address extension. </dd>

<dt>$domain</dt>

<dd>The recipient domain. </dd>

<dt>$local</dt>

<dd>The entire recipient localpart. </dd>

<dt>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></dt>

<dd>The address extension delimiter that was found in the recipient
address (Postfix 2.11 and later), or the system-wide recipient
address extension delimiter (Postfix 2.10 and earlier). </dd>

<dt>${name?value}</dt>

<dt>${name?{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is non-empty. </dd>

<dt>${name:value}</dt>

<dt>${name:{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is empty. </dd>

<dt>${name?{value1}:{value2}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value1 when $name is non-empty,
value2 otherwise. </dd>

</dl>


Instead of $name you can also specify ${name} or $(name).


 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="command_expansion_filter">command_expansion_filter</a>
(default: see "postconf -d" output)</DT><DD>


Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows in
$name expansions of $<a href="postconf.5.html#mailbox_command">mailbox_command</a> and $<a href="postconf.5.html#command_execution_directory">command_execution_directory</a>.
Characters outside the
allowed set are replaced by underscores.


</DD>

<DT><a name="command_time_limit">command_time_limit</a>
(default: 1000s)</DT><DD>


Time limit for delivery to external commands. This limit is used
by the <a href="local.8.html">local(8)</a> delivery agent, and is the default time limit for
delivery by the <a href="pipe.8.html">pipe(8)</a> delivery agent.



Note: if you set this time limit to a large value you must update the
global <a href="postconf.5.html#ipc_timeout">ipc_timeout</a> parameter as well.


</DD>

<DT><a name="compatibility_level">compatibility_level</a>
(default: 0)</DT><DD>

 A safety net that causes Postfix to run with backwards-compatible
default settings after an upgrade to a newer Postfix version. 

 With backwards compatibility turned on (the <a href="postconf.5.html">main.cf</a> <a href="postconf.5.html#compatibility_level">compatibility_level</a>
value is less than the Postfix built-in value), Postfix looks for
settings that are left at their implicit default value, and logs a
message when a backwards-compatible default setting is required.


<blockquote>
<pre>
using backwards-compatible default setting name=value
 to [accept a specific client request]

using backwards-compatible default setting name=value
 to [enable specific Postfix behavior]
</pre>
</blockquote>

 See <a href="COMPATIBILITY_README.html">COMPATIBILITY_README</a> for specific message details. If such
a message is logged in the context of a legitimate request, the
system administrator should make the backwards-compatible setting
permanent in <a href="postconf.5.html">main.cf</a> or <a href="master.5.html">master.cf</a>, for example: 

<blockquote>
<pre>
# postconf name=value
# postfix reload
</pre>
</blockquote>

 When no more backwards-compatible settings need to be made
permanent, the administrator should turn off backwards compatibility
by updating the <a href="postconf.5.html#compatibility_level">compatibility_level</a> setting in <a href="postconf.5.html">main.cf</a>:

<blockquote>
<pre>
# postconf <a href="postconf.5.html#compatibility_level">compatibility_level</a>=N
# postfix reload
</pre>
</blockquote>

 For N specify the number that is logged in your <a href="postfix.1.html">postfix(1)</a>
warning message: 

<blockquote>
<pre>
warning: To disable backwards compatibility use "postconf
 <a href="postconf.5.html#compatibility_level">compatibility_level</a>=N" and "postfix reload"
</pre>
</blockquote>

 Starting with Postfix version 3.6, the compatibility level in
the above warning message is the Postfix version that introduced
the last incompatible change. The level is formatted as
major.minor.patch, where patch is usually omitted and
defaults to zero. Earlier compatibility levels are 0, 1 and 2. 

 NOTE: this also introduces support for the "<level",
"<=level", and other operators to compare compatibility levels.
With the standard operators "<", "<=", etc., compatibility
level "3.10" would be smaller than "3.9" which is undesirable. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="config_directory">config_directory</a>
(default: see "postconf -d" output)</DT><DD>

 The default location of the Postfix <a href="postconf.5.html">main.cf</a> and <a href="master.5.html">master.cf</a>
configuration files. This can be overruled via the following
mechanisms: 

<ul>

<li> The MAIL_CONFIG environment variable (daemon processes
and commands). 

<li> The "-c" command-line option (commands only). 

</ul>

 With Postfix commands that run with set-gid privileges, a
<a href="postconf.5.html#config_directory">config_directory</a> override either requires root privileges, or it
requires that the directory is listed with the <a href="postconf.5.html#alternate_config_directories">alternate_config_directories</a>
parameter in the default <a href="postconf.5.html">main.cf</a> file. 

</DD>

<DT><a name="confirm_delay_cleared">confirm_delay_cleared</a>
(default: no)</DT><DD>

 After sending a "your message is delayed" notification, inform
the sender when the delay clears up. This can result in a sudden
burst of notifications at the end of a prolonged network outage,
and is therefore disabled by default. 

 See also: <a href="postconf.5.html#delay_warning_time">delay_warning_time</a>. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="connection_cache_protocol_timeout">connection_cache_protocol_timeout</a>
(default: 5s)</DT><DD>

 Time limit for connection cache connect, send or receive
operations. The time limit is enforced in the client. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="connection_cache_service_name">connection_cache_service_name</a>
(default: scache)</DT><DD>

 The name of the <a href="scache.8.html">scache(8)</a> connection cache service. This service
maintains a limited pool of cached sessions. 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="connection_cache_status_update_time">connection_cache_status_update_time</a>
(default: 600s)</DT><DD>

 How frequently the <a href="scache.8.html">scache(8)</a> server logs usage statistics with
connection cache hit and miss rates for logical destinations and for
physical endpoints. 

</DD>

<DT><a name="connection_cache_ttl_limit">connection_cache_ttl_limit</a>
(default: 2s)</DT><DD>

 The maximal time-to-live value that the <a href="scache.8.html">scache(8)</a> connection
cache server
allows. Requests that specify a larger TTL will be stored with the
maximum allowed TTL. The purpose of this additional control is to
protect the infrastructure against careless people. The cache TTL
is already bounded by $<a href="postconf.5.html#max_idle">max_idle</a>. 

</DD>

<DT><a name="content_filter">content_filter</a>
(default: empty)</DT><DD>

 After the message is queued, send the entire message to the
specified transport:destination. The transport name
specifies the first field of a mail delivery agent definition in
<a href="master.5.html">master.cf</a>; the syntax of the next-hop destination is described
in the manual page of the corresponding delivery agent. More
information about external content filters is in the Postfix
<a href="FILTER_README.html">FILTER_README</a> file. 

 Notes: 

<ul>

<li> This setting has lower precedence than a FILTER action
that is specified in an <a href="access.5.html">access(5)</a>, <a href="header_checks.5.html">header_checks(5)</a> or <a href="header_checks.5.html">body_checks(5)</a>
table. 

<li> The meaning of an empty next-hop filter destination
is version dependent. Postfix 2.7 and later will use the recipient
domain; earlier versions will use $<a href="postconf.5.html#myhostname">myhostname</a>. Specify
"<a href="postconf.5.html#default_filter_nexthop">default_filter_nexthop</a> = $<a href="postconf.5.html#myhostname">myhostname</a>" for compatibility with Postfix
2.6 or earlier, or specify a <a href="postconf.5.html#content_filter">content_filter</a> value with an explicit
next-hop destination. 

</ul>

</DD>

<DT><a name="cyrus_sasl_config_path">cyrus_sasl_config_path</a>
(default: empty)</DT><DD>

 Search path for Cyrus SASL application configuration files,
currently used only to locate the $<a href="postconf.5.html#smtpd_sasl_path">smtpd_sasl_path</a>.conf file.
Specify zero or more directories separated by a colon character,
or an empty value to use Cyrus SASL's built-in search path. 

 Note: some Debian-based Postfix distributions ignore the
"<a href="postconf.5.html#cyrus_sasl_config_path">cyrus_sasl_config_path</a>" parameter setting, and force Postfix to
open the file <code>/etc/postfix/sasl/smtpd.conf</code>. 

 This feature is available in Postfix 2.5 and later when compiled
with Cyrus SASL 2.1.22 or later. 

</DD>

<DT><a name="daemon_directory">daemon_directory</a>
(default: see "postconf -d" output)</DT><DD>


The directory with Postfix support programs and daemon programs.
These should not be invoked directly by humans. The directory must
be owned by root.


</DD>

<DT><a name="daemon_table_open_error_is_fatal">daemon_table_open_error_is_fatal</a>
(default: no)</DT><DD>

 How a Postfix daemon process handles errors while opening lookup
tables: gradual degradation or immediate termination. 

<dl>

<dt> no (default) </dt> <dd> Gradual degradation: a
daemon process logs a message of type "error" and continues execution
with reduced functionality. Features that do not depend on the
unavailable table will work normally, while features that depend
on the table will result in a type "warning" message. When
the <a href="postconf.5.html#notify_classes">notify_classes</a> parameter value contains the "data" class, the
Postfix SMTP server and client will report transcripts of sessions
with an error because a table is unavailable. </dd>

<dt> yes (historical behavior) </dt> <dd> Immediate
termination: a daemon process logs a type "fatal" message and
terminates immediately. This option reduces the number of possible
code paths through Postfix, and may therefore be slightly more
secure than the default. </dd>

</dl>

 For the sake of sanity, the number of type "error" messages is
limited to 13 over the lifetime of a daemon process. 

 This feature is available in Postfix 2.9 and later. 

</DD>

<DT><a name="daemon_timeout">daemon_timeout</a>
(default: 18000s)</DT><DD>

 How much time a Postfix daemon process may take to handle a
request before it is terminated by a built-in watchdog timer. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="data_directory">data_directory</a>
(default: see "postconf -d" output)</DT><DD>

 The directory with Postfix-writable data files (for example:
caches, pseudo-random numbers). This directory must be owned by
the <a href="postconf.5.html#mail_owner">mail_owner</a> account, and must not be shared with non-Postfix
software. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="debug_peer_level">debug_peer_level</a>
(default: 2)</DT><DD>

 The increment in verbose logging level when a nexthop destination,
remote client or server name or network address matches a pattern
given with the <a href="postconf.5.html#debug_peer_list">debug_peer_list</a> parameter. 

 Per-nexthop debug logging is available in Postfix 3.6 and later. 

</DD>

<DT><a name="debug_peer_list">debug_peer_list</a>
(default: empty)</DT><DD>

 Optional list of nexthop destination, remote client or server
name or network address patterns that, if matched, cause the verbose
logging level to increase by the amount specified in $<a href="postconf.5.html#debug_peer_level">debug_peer_level</a>.


 Per-nexthop debug logging is available in Postfix 3.6 and later. 

 Specify domain names, network/netmask patterns, "/file/name"
patterns or "<a href="DATABASE_README.html">type:table</a>" lookup tables. The right-hand side result
from "<a href="DATABASE_README.html">type:table</a>" lookups is ignored. An IPv6 address must be enclosed
in <tt>[]</tt>. 

 Pattern matching of domain names is controlled by the presence
or absence of "<a href="postconf.5.html#debug_peer_list">debug_peer_list</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
parameter value. 


Examples:


<pre>
<a href="postconf.5.html#debug_peer_list">debug_peer_list</a> = 127.0.0.1
<a href="postconf.5.html#debug_peer_list">debug_peer_list</a> = example.com
</pre>

</DD>

<DT><a name="debugger_command">debugger_command</a>
(default: empty)</DT><DD>


The external command to execute when a Postfix daemon program is
invoked with the -D option.



Use "command .. & sleep 5" so that the debugger can attach before
the process marches on. If you use an X-based debugger, be sure to
set up your XAUTHORITY environment variable before starting Postfix.



Note: the command is subject to $name expansion, before it is
passed to the default command interpreter. Specify "$$" to
produce a single "$" character.



Example:


<pre>
<a href="postconf.5.html#debugger_command">debugger_command</a> =
 PATH=/usr/bin:/usr/X11R6/bin
 ddd $<a href="postconf.5.html#daemon_directory">daemon_directory</a>/$<a href="postconf.5.html#process_name">process_name</a> $<a href="postconf.5.html#process_id">process_id</a> & sleep 5
</pre>

</DD>

<DT><a name="default_cache_db_type">default_cache_db_type</a>
(default: see 'postconf -d <a href="postconf.5.html#default_cache_db_type">default_cache_db_type</a>' output)</DT><DD>

 The default database type for <a href="postconf.5.html#address_verify_map">address_verify_map</a> and
<a href="postconf.5.html#postscreen_cache_map">postscreen_cache_map</a>. Before Postfix 3.11 those caches used btree
by default. 

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="default_database_type">default_database_type</a>
(default: see "postconf -d" output)</DT><DD>


The default database type for use in <a href="newaliases.1.html">newaliases(1)</a>, <a href="postalias.1.html">postalias(1)</a>
and <a href="postmap.1.html">postmap(1)</a> commands. On many UNIX systems the default type is
either lmdb or hash. The default setting is frozen
when the Postfix system is built.



Examples:


<pre>
<a href="postconf.5.html#default_database_type">default_database_type</a> = lmdb
<a href="postconf.5.html#default_database_type">default_database_type</a> = hash
</pre>

</DD>

<DT><a name="default_delivery_slot_cost">default_delivery_slot_cost</a>
(default: 5)</DT><DD>


How often the Postfix queue manager's scheduler is allowed to
preempt delivery of one message with another.



Each transport maintains a so-called "available delivery slot counter"
for each message. One message can be preempted by another one when
the other message can be delivered using no more delivery slots
(i.e., invocations of delivery agents) than the current message
counter has accumulated (or will eventually accumulate - see about
slot loans below). This parameter controls how often the counter is
incremented - it happens after each <a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a>
recipients have been delivered.



The cost of 0 is used to disable the preempting scheduling completely.
The minimum value the scheduling algorithm can use is 2 - use it
if you want to maximize the message throughput rate. Although there
is no maximum, it doesn't make much sense to use values above say
50.



The only reason why the value of 2 is not the default is the way
this parameter affects the delivery of mailing-list mail. In the
worst case, delivery can take somewhere between (cost+1/cost)
and (cost/cost-1) times more than if the preemptive scheduler was
disabled. The default value of 5 turns out to provide reasonable
message response times while making sure the mailing-list deliveries
are not extended by more than 20-25 percent even in the worst case.


 Use <a href="postconf.5.html#transport_delivery_slot_cost">transport_delivery_slot_cost</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.



Examples:


<pre>
<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a> = 0
<a href="postconf.5.html#default_delivery_slot_cost">default_delivery_slot_cost</a> = 2
</pre>

</DD>

<DT><a name="default_delivery_slot_discount">default_delivery_slot_discount</a>
(default: 50)</DT><DD>


The default value for transport-specific _delivery_slot_discount
settings.



This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
<a href="postconf.5.html#transport_delivery_slot_discount">transport_delivery_slot_discount</a> percent of the required amount
plus <a href="postconf.5.html#transport_delivery_slot_loan">transport_delivery_slot_loan</a> still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.


 Use <a href="postconf.5.html#transport_delivery_slot_discount">transport_delivery_slot_discount</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


</DD>

<DT><a name="default_delivery_slot_loan">default_delivery_slot_loan</a>
(default: 3)</DT><DD>


The default value for transport-specific _delivery_slot_loan
settings.



This parameter speeds up the moment when a message preemption can
happen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when
<a href="postconf.5.html#transport_delivery_slot_discount">transport_delivery_slot_discount</a> percent of the required amount
plus <a href="postconf.5.html#transport_delivery_slot_loan">transport_delivery_slot_loan</a> still remains to be accumulated.
Note that the full amount will still have to be accumulated before
another preemption can take place later.


 Use <a href="postconf.5.html#transport_delivery_slot_loan">transport_delivery_slot_loan</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


</DD>

<DT><a name="default_delivery_status_filter">default_delivery_status_filter</a>
(default: empty)</DT><DD>

 Optional filter in Postfix delivery agents, to replace the
delivery status code or explanatory text of successful or unsuccessful
deliveries. This allows the replacement of a temporary error status
code (4.X.X) with a permanent error status code (5.X.X) or vice
versa, but does not allow
the replacement of a successful status code (2.X.X) with an
unsuccessful status code (4.X.X or 5.X.X) or vice versa. 

 Note: the (smtp|lmtp)_delivery_status_filter is applied only
once per recipient: when delivery is successful, when delivery is
rejected with 5XX, or when there are no more alternate MX or A
destinations. Use <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a> or <a href="postconf.5.html#lmtp_reply_filter">lmtp_reply_filter</a> to inspect
responses for all delivery attempts. 

 The following parameters can be used to implement a filter for
specific delivery agents: <a href="postconf.5.html#lmtp_delivery_status_filter">lmtp_delivery_status_filter</a>,
<a href="postconf.5.html#local_delivery_status_filter">local_delivery_status_filter</a>, <a href="postconf.5.html#pipe_delivery_status_filter">pipe_delivery_status_filter</a>,
<a href="postconf.5.html#smtp_delivery_status_filter">smtp_delivery_status_filter</a> or <a href="postconf.5.html#virtual_delivery_status_filter">virtual_delivery_status_filter</a>. These
parameters support the same filter syntax as described here. 

 Specify zero or more "<a href="DATABASE_README.html">type:table</a>" lookup table names, separated
by comma or whitespace. For each successful or unsuccessful delivery
to a recipient, the tables are queried in the specified order with
one line of text that is structured as follows: 

<blockquote>
enhanced-status-code SPACE explanatory-text
</blockquote>

 The first table match wins. The lookup result must have the
same structure as the query, a successful status code (2.X.X) must
be replaced with a successful status code, an unsuccessful status
code (4.X.X or 5.X.X) must be replaced with an unsuccessful status
code, and the explanatory text field must be non-empty. Other results
will result in a warning. 

 Example 1: convert specific soft TLS errors into hard errors,
by overriding the first number in the enhanced status code. 

<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#smtp_delivery_status_filter">smtp_delivery_status_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/smtp_dsn_filter
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/smtp_dsn_filter:
 /^4(\.\d+\.\d+ TLS is required, but host \S+ refused to start TLS: .+)/
 5$1
 /^4(\.\d+\.\d+ TLS is required, but was not offered by host .+)/
 5$1
 # Do not change the following into hard bounces. They may
 # result from a local configuration problem.
 # 4.\d+.\d+ TLS is required, but our TLS engine is unavailable
 # 4.\d+.\d+ TLS is required, but unavailable
 # 4.\d+.\d+ Cannot start TLS: handshake failure
</pre>
</blockquote>

 Example 2: censor the per-recipient delivery status text so
that it does not reveal the destination command or filename
when a remote sender requests confirmation of successful delivery.


<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#local_delivery_status_filter">local_delivery_status_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/local_dsn_filter
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/local_dsn_filter:
 /^(2\S+ delivered to file).+/ $1
 /^(2\S+ delivered to command).+/ $1
</pre>
</blockquote>

 Notes: 

<ul>

<li> This feature will NOT override the <a href="postconf.5.html#soft_bounce">soft_bounce</a> safety net. 

<li> This feature will change the enhanced status code and text
that is logged to the maillog file, and that is reported to the
sender in delivery confirmation or non-delivery notifications.


</ul>

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a>
(default: 1)</DT><DD>

 How many pseudo-cohorts must suffer connection or handshake
failure before a specific destination is considered unavailable
(and further delivery is suspended). Specify zero to disable this
feature. A destination's pseudo-cohort failure count is reset each
time a delivery completes without connection or handshake failure
for that specific destination. 

 A pseudo-cohort is the number of deliveries equal to a destination's
delivery concurrency. 

 Use <a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit">transport_destination_concurrency_failed_cohort_limit</a> to specify
a transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport. 

 This feature is available in Postfix 2.5. The default setting
is compatible with earlier Postfix versions. 

</DD>

<DT><a name="default_destination_concurrency_limit">default_destination_concurrency_limit</a>
(default: 20)</DT><DD>


The default maximal number of parallel deliveries to the same
destination. This is the default limit for delivery via the <a href="lmtp.8.html">lmtp(8)</a>,
<a href="pipe.8.html">pipe(8)</a>, <a href="smtp.8.html">smtp(8)</a> and <a href="virtual.8.html">virtual(8)</a> delivery agents.
With a per-destination recipient limit > 1, a destination is a domain,
otherwise it is a recipient.


 Use <a href="postconf.5.html#transport_destination_concurrency_limit">transport_destination_concurrency_limit</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


</DD>

<DT><a name="default_destination_concurrency_negative_feedback">default_destination_concurrency_negative_feedback</a>
(default: 1)</DT><DD>

 The per-destination amount of delivery concurrency negative
feedback, after a delivery completes with a connection or handshake
failure. Feedback values are in the range 0..1 inclusive. With
negative feedback, concurrency is decremented at the beginning of
a sequence of length 1/feedback. This is unlike positive feedback,
where concurrency is incremented at the end of a sequence of length
1/feedback. 

 As of Postfix version 2.5, negative feedback cannot reduce
delivery concurrency to zero. Instead, a destination is marked
dead (further delivery suspended) after the failed pseudo-cohort
count reaches $<a href="postconf.5.html#default_destination_concurrency_failed_cohort_limit">default_destination_concurrency_failed_cohort_limit</a>
(or $<a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit">transport_destination_concurrency_failed_cohort_limit</a>).
To make the scheduler completely immune to connection or handshake
failures, specify a zero feedback value and a zero failed pseudo-cohort
limit. 

 Specify one of the following forms: 

<dl>

<dt> number </dt>

<dt> number / number </dt>

<dd> Constant feedback. The value must be in the range 0..1 inclusive.
The default setting of "1" is compatible with Postfix versions
before 2.5, where a destination's delivery concurrency is throttled
down to zero (and further delivery suspended) after a single failed
pseudo-cohort. </dd>

<dt> number / concurrency </dt>

<dd> Variable feedback of "number / (delivery concurrency)".
The number must be in the range 0..1 inclusive. With
number equal to "1", a destination's delivery concurrency
is decremented by 1 after each failed pseudo-cohort. </dd>

</dl>

 A pseudo-cohort is the number of deliveries equal to a destination's
delivery concurrency. 

 Use <a href="postconf.5.html#transport_destination_concurrency_negative_feedback">transport_destination_concurrency_negative_feedback</a>
to specify a transport-specific override, where transport
is the <a href="master.5.html">master.cf</a>
name of the message delivery transport. 

 This feature is available in Postfix 2.5. The default setting
is compatible with earlier Postfix versions. 

</DD>

<DT><a name="default_destination_concurrency_positive_feedback">default_destination_concurrency_positive_feedback</a>
(default: 1)</DT><DD>

 The per-destination amount of delivery concurrency positive
feedback, after a delivery completes without connection or handshake
failure. Feedback values are in the range 0..1 inclusive. The
concurrency increases until it reaches the per-destination maximal
concurrency limit. With positive feedback, concurrency is incremented
at the end of a sequence with length 1/feedback. This is unlike
negative feedback, where concurrency is decremented at the start
of a sequence of length 1/feedback. 

 Specify one of the following forms: 

<dl>

<dt> number </dt>

<dt> number / number </dt>

<dd> Constant feedback. The value must be in the range 0..1
inclusive. The default setting of "1" is compatible with Postfix
versions before 2.5, where a destination's delivery concurrency
doubles after each successful pseudo-cohort. </dd>

<dt> number / concurrency </dt>

<dd> Variable feedback of "number / (delivery concurrency)".
The number must be in the range 0..1 inclusive. With
number equal to "1", a destination's delivery concurrency
is incremented by 1 after each successful pseudo-cohort. </dd>

</dl>

 A pseudo-cohort is the number of deliveries equal to a destination's
delivery concurrency. 

 Use <a href="postconf.5.html#transport_destination_concurrency_positive_feedback">transport_destination_concurrency_positive_feedback</a>
to specify a transport-specific override, where transport
is the <a href="master.5.html">master.cf</a> name of the message delivery transport. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="default_destination_rate_delay">default_destination_rate_delay</a>
(default: 0s)</DT><DD>

 The default amount of delay that is inserted between individual
message deliveries to the same destination and over the same message
delivery transport. Specify a non-zero value to rate-limit those
message deliveries to at most one per $<a href="postconf.5.html#default_destination_rate_delay">default_destination_rate_delay</a>.


 The resulting behavior depends on the value of the corresponding
per-destination recipient limit.



<ul>

<li> With a corresponding per-destination recipient limit >
1, the rate delay specifies the time between deliveries to the
same domain. Different domains are delivered in parallel,
subject to the process limits specified in <a href="master.5.html">master.cf</a>. 

<li> With a corresponding per-destination recipient limit equal
to 1, the rate delay specifies the time between deliveries to the
same recipient. Different recipients are delivered in
parallel, subject to the process limits specified in <a href="master.5.html">master.cf</a>.


</ul>

 To enable the delay, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit). 

 Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds). 

 NOTE: the delay is enforced by the queue manager. The delay
timer state does not survive "postfix reload" or "postfix
stop".


 Use <a href="postconf.5.html#transport_destination_rate_delay">transport_destination_rate_delay</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


 NOTE: with a non-zero _destination_rate_delay, specify a
<a href="postconf.5.html#transport_destination_concurrency_failed_cohort_limit">transport_destination_concurrency_failed_cohort_limit</a> of 10
or more to prevent Postfix from deferring all mail for the same
destination after only one connection or handshake error. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="default_destination_recipient_limit">default_destination_recipient_limit</a>
(default: 50)</DT><DD>


The default maximal number of recipients per message delivery.
This is the default limit for delivery via the <a href="lmtp.8.html">lmtp(8)</a>, <a href="pipe.8.html">pipe(8)</a>,
<a href="smtp.8.html">smtp(8)</a> and <a href="virtual.8.html">virtual(8)</a> delivery agents.


 Setting this parameter to a value of 1 affects email deliveries
as follows:

<ul>

<li> It changes the meaning of the corresponding per-destination
concurrency limit, from concurrency of deliveries to the same
domain into concurrency of deliveries to the same recipient.
Different recipients are delivered in parallel, subject to the
process limits specified in <a href="master.5.html">master.cf</a>. 

<li> It changes the meaning of the corresponding per-destination
rate delay, from the delay between deliveries to the same
domain into the delay between deliveries to the same
recipient. Again, different recipients are delivered in parallel,
subject to the process limits specified in <a href="master.5.html">master.cf</a>. 

<li> It changes the meaning of other corresponding per-destination
settings in a similar manner, from settings for delivery to the
same domain into settings for delivery to the same
recipient.

</ul>

 Use <a href="postconf.5.html#transport_destination_recipient_limit">transport_destination_recipient_limit</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


</DD>

<DT><a name="default_extra_recipient_limit">default_extra_recipient_limit</a>
(default: 1000)</DT><DD>


The default value for the extra per-transport limit imposed on the
number of in-memory recipients. This extra recipient space is
reserved for the cases when the Postfix queue manager's scheduler
preempts one message with another and suddenly needs some extra
recipient slots for the chosen message in order to avoid performance
degradation.


 Use <a href="postconf.5.html#transport_extra_recipient_limit">transport_extra_recipient_limit</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


</DD>

<DT><a name="default_filter_nexthop">default_filter_nexthop</a>
(default: empty)</DT><DD>

 When a <a href="postconf.5.html#content_filter">content_filter</a> or FILTER request specifies no explicit
next-hop destination, use $<a href="postconf.5.html#default_filter_nexthop">default_filter_nexthop</a> instead; when
that value is empty, use the domain in the recipient address.
Specify "<a href="postconf.5.html#default_filter_nexthop">default_filter_nexthop</a> = $<a href="postconf.5.html#myhostname">myhostname</a>" for compatibility
with Postfix version 2.6 and earlier, or specify an explicit next-hop
destination with each <a href="postconf.5.html#content_filter">content_filter</a> value or FILTER action. 

 This feature is available in Postfix 2.7 and later. 

</DD>

<DT><a name="default_minimum_delivery_slots">default_minimum_delivery_slots</a>
(default: 3)</DT><DD>


How many recipients a message must have in order to invoke the
Postfix queue manager's scheduling algorithm at all. Messages
which would never accumulate at least this many delivery slots
(subject to slot cost parameter as well) are never preempted.


 Use <a href="postconf.5.html#transport_minimum_delivery_slots">transport_minimum_delivery_slots</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


</DD>

<DT><a name="default_privs">default_privs</a>
(default: nobody)</DT><DD>


The default rights used by the <a href="local.8.html">local(8)</a> delivery agent for delivery
to an external file or command. These rights are used when delivery
is requested from an <a href="aliases.5.html">aliases(5)</a> file that is owned by root, or
when delivery is done on behalf of root. DO NOT SPECIFY A
PRIVILEGED USER OR THE POSTFIX OWNER.


</DD>

<DT><a name="default_process_limit">default_process_limit</a>
(default: 100)</DT><DD>


The default maximal number of Postfix child processes that provide
a given service. This limit can be overruled for specific services
in the <a href="master.5.html">master.cf</a> file.


</DD>

<DT><a name="default_rbl_reply">default_rbl_reply</a>
(default: see "postconf -d" output)</DT><DD>


The default Postfix SMTP server response template for a request that is
rejected by an RBL-based restriction. This template can be overruled
by specific entries in the optional <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> lookup table.



This feature is available in Postfix 2.0 and later.



The template does not support Postfix configuration parameter $name
substitution. Instead, it supports exactly one level of $name
substitution for the following attributes:


<dl>

<dt>$client</dt>

<dd>The client hostname and IP address, formatted as name[address]. </dd>

<dt>$client_address</dt>

<dd>The client IP address. </dd>

<dt>$client_name</dt>

<dd>The client hostname or "unknown". See <a href="postconf.5.html#reject_unknown_client_hostname">reject_unknown_client_hostname</a>
for more details. </dd>

<dt>$reverse_client_name</dt>

<dd>The client hostname from address->name lookup, or "unknown".
See <a href="postconf.5.html#reject_unknown_reverse_client_hostname">reject_unknown_reverse_client_hostname</a> for more details. </dd>

<dt>$helo_name</dt>

<dd>The hostname given in HELO or EHLO command or empty string. </dd>

<dt>$rbl_class</dt>

<dd>The denylisted entity type: Client host, Helo command, Sender
address, or Recipient address. </dd>

<dt>$rbl_code</dt>

<dd>The numerical SMTP response code, as specified with the
<a href="postconf.5.html#maps_rbl_reject_code">maps_rbl_reject_code</a> configuration parameter. Note: The numerical
SMTP response code is required, and must appear at the start of the
reply. With Postfix version 2.3 and later this information may be followed
by an <a href="https://tools.ietf.org/html/rfc3463">RFC 3463</a> enhanced status code. </dd>

<dt>$rbl_domain</dt>

<dd>The RBL domain (without any =address-filter) where
$rbl_what is denylisted. </dd>

<dt>$rbl_reason</dt>

<dd>The reason why $rbl_what is denylisted, or an empty string. </dd>

<dt>$rbl_what</dt>

<dd>The entity that is denylisted (an IP address, a hostname, a domain
name, or an email address whose domain was denylisted). </dd>

<dt>$recipient</dt>

<dd>The recipient address or <> in case of the null address. </dd>

<dt>$recipient_domain</dt>

<dd>The recipient domain or empty string. </dd>

<dt>$recipient_name</dt>

<dd>The recipient address localpart or <> in case of null address. </dd>

<dt>$sender</dt>

<dd>The sender address or <> in case of the null address. </dd>

<dt>$sender_domain</dt>

<dd>The sender domain or empty string. </dd>

<dt>$sender_name</dt>

<dd>The sender address localpart or <> in case of the null address. </dd>

<dt>${name?value}</dt>

<dt>${name?{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is non-empty. </dd>

<dt>${name:value}</dt>

<dt>${name:{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is empty. </dd>

<dt>${name?{value1}:{value2}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value1 when $name is non-empty,
value2 otherwise. </dd>

</dl>


Instead of $name you can also specify ${name} or $(name).


 Note: when an enhanced status code is specified in an RBL reply
template, it is subject to modification. The following transformations
are needed when the same RBL response template is used for client,
helo, sender, or recipient access restrictions. 

<ul>

<li> When rejecting a sender address, the Postfix SMTP server
will transform a recipient DSN status (e.g., 4.1.1-4.1.6) into the
corresponding sender DSN status, and vice versa. 

<li> When rejecting non-address information (such as the HELO
command argument or the client hostname/address), the Postfix SMTP
server will transform a sender or recipient DSN status into a generic
non-address DSN status (e.g., 4.0.0). 

</ul>

</DD>

<DT><a name="default_recipient_limit">default_recipient_limit</a>
(default: 20000)</DT><DD>


The default per-transport upper limit on the number of in-memory
recipients. These limits take priority over the global
<a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> after the message has been assigned
to the respective transports. See also <a href="postconf.5.html#default_extra_recipient_limit">default_extra_recipient_limit</a>
and <a href="postconf.5.html#qmgr_message_recipient_minimum">qmgr_message_recipient_minimum</a>.


 Use <a href="postconf.5.html#transport_recipient_limit">transport_recipient_limit</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


</DD>

<DT><a name="default_recipient_refill_delay">default_recipient_refill_delay</a>
(default: 5s)</DT><DD>


The default per-transport maximum delay between refilling recipients.
When not all message recipients fit into memory at once, keep loading
more of them at least once every this many seconds. This is used to
make sure the recipients are refilled in a timely manner even when
$<a href="postconf.5.html#default_recipient_refill_limit">default_recipient_refill_limit</a> is too high for too slow deliveries.


 Use <a href="postconf.5.html#transport_recipient_refill_delay">transport_recipient_refill_delay</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


 This feature is available in Postfix 2.4 and later. 

</DD>

<DT><a name="default_recipient_refill_limit">default_recipient_refill_limit</a>
(default: 100)</DT><DD>


The default per-transport limit on the number of recipients refilled at
once. When not all message recipients fit into memory at once, keep
loading more of them in batches of at least this many at a time. See also
$<a href="postconf.5.html#default_recipient_refill_delay">default_recipient_refill_delay</a>, which may result in recipient batches
lower than this when this limit is too high for too slow deliveries.


 Use <a href="postconf.5.html#transport_recipient_refill_limit">transport_recipient_refill_limit</a> to specify a
transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport.


 This feature is available in Postfix 2.4 and later. 

</DD>

<DT><a name="default_transport">default_transport</a>
(default: smtp)</DT><DD>


The default mail delivery transport and next-hop destination for
the <a href="ADDRESS_CLASS_README.html#default_domain_class">default domain</a> class: recipient domains that do not match
$<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>,
$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>,
or $<a href="postconf.5.html#relay_domains">relay_domains</a>. This information will not be used when
<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> returns a result, and may
be overridden with the <a href="transport.5.html">transport(5)</a> table. 

 For recipient domains in the <a href="ADDRESS_CLASS_README.html#default_domain_class">default domain</a> class: 

<ul>

<li> In order of decreasing precedence, the delivery transport
is taken from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2)
$<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> or $<a href="postconf.5.html#default_transport">default_transport</a>.


<li> In order of decreasing precedence, the nexthop destination
is taken from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2)
$<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> or $<a href="postconf.5.html#default_transport">default_transport</a>, 3)
$<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> or $<a href="postconf.5.html#relayhost">relayhost</a> or the recipient
domain. 

</ul>


Specify a string of the form transport:nexthop, where transport
is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
The :nexthop destination is optional; its syntax is documented
in the manual page of the corresponding delivery agent. In the case of
SMTP or LMTP, specify one or more destinations separated by comma or
whitespace (with Postfix 3.5 and later).



Example:


<pre>
<a href="postconf.5.html#default_transport">default_transport</a> = uucp:relayhostname
</pre>

</DD>

<DT><a name="default_transport_rate_delay">default_transport_rate_delay</a>
(default: 0s)</DT><DD>

 The default amount of delay that is inserted between individual
message deliveries over the same message delivery transport,
regardless of destination. Specify a non-zero value to rate-limit
those message deliveries to at most one per $<a href="postconf.5.html#default_transport_rate_delay">default_transport_rate_delay</a>.


Use <a href="postconf.5.html#transport_transport_rate_delay">transport_transport_rate_delay</a> to specify a
transport-specific override, where the initial transport is
the <a href="master.5.html">master.cf</a> name of the message delivery transport. 

 Example: throttle outbound SMTP mail to at most 3 deliveries
per minute. 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 smtp_transport_rate_delay = 20s
</pre>

 To enable the delay, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit). 

 Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds). 

 NOTE: the delay is enforced by the queue manager. 

 This feature is available in Postfix 3.1 and later. 

</DD>

<DT><a name="default_verp_delimiters">default_verp_delimiters</a>
(default: +=)</DT><DD>

 The two default VERP delimiter characters. These are used when
no explicit delimiters are specified with the SMTP XVERP command
or with the "sendmail -XV" command-line option (Postfix 2.2
and earlier: -V). Specify characters that are allowed by the
<a href="postconf.5.html#verp_delimiter_filter">verp_delimiter_filter</a> setting.



This feature is available in Postfix 1.1 and later.


</DD>

<DT><a name="defer_code">defer_code</a>
(default: 450)</DT><DD>


The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the "defer" restriction.



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.


</DD>

<DT><a name="defer_service_name">defer_service_name</a>
(default: defer)</DT><DD>


The name of the defer service. This service is implemented by the
<a href="bounce.8.html">bounce(8)</a> daemon and maintains a record
of failed delivery attempts and generates non-delivery notifications.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="defer_transports">defer_transports</a>
(default: empty)</DT><DD>


The names of message delivery transports that should not deliver mail
unless someone issues "sendmail -q" or equivalent. Specify zero
or more mail delivery transport names that appear in the
first field of <a href="master.5.html">master.cf</a>.



Example:


<pre>
<a href="postconf.5.html#defer_transports">defer_transports</a> = smtp
</pre>

</DD>

<DT><a name="delay_logging_resolution_limit">delay_logging_resolution_limit</a>
(default: 2)</DT><DD>

 The maximal number of digits after the decimal point when logging
delay values. Specify a number in the range 0..6. 

 To improve readability, delays are logged with only a limited
number of significant digits: 

<ul>

<li> Delays ≥ 100s are rounded off to an integral number of
seconds.

<li> Delays < 10-$<a href="postconf.5.html#delay_logging_resolution_limit">delay_logging_resolution_limit</a> are
rounded off to "0".

<li> Other delays are rounded off to two significant digits, or
fewer if the result would exceed the <a href="postconf.5.html#delay_logging_resolution_limit">delay_logging_resolution_limit</a>.

</ul>

 The format of the "delays=a/b/c/d" logging is as follows: 

<ul>

<li> a = Time from message arrival to last <a href="QSHAPE_README.html#active_queue">active queue</a> entry.

<li> b = Time from last <a href="QSHAPE_README.html#active_queue">active queue</a> entry to the beginning of
connection setup.

<li> c = Time in connection setup. With SMTP, that is the time
before sending the MAIL FROM command: with a new connection, that
includes DNS lookups, and protocol handshakes with TCP, EHLO, and
STARTTLS; with a reused connection, that includes DNS lookups,
connection cache lookup by domain or IP address, and a liveness
probe with RSET.

<li> d = Time in message transmission. With SMTP, that starts with
sending MAIL FROM.

</ul>

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="delay_notice_recipient">delay_notice_recipient</a>
(default: postmaster)</DT><DD>


The recipient of postmaster notifications with the message headers
of mail that cannot be delivered within $<a href="postconf.5.html#delay_warning_time">delay_warning_time</a> time
units. 


See also: <a href="postconf.5.html#delay_warning_time">delay_warning_time</a>, <a href="postconf.5.html#notify_classes">notify_classes</a>.


</DD>

<DT><a name="delay_warning_time">delay_warning_time</a>
(default: 0h)</DT><DD>


The time after which the sender receives a copy of the message
headers of mail that is still queued. The <a href="postconf.5.html#confirm_delay_cleared">confirm_delay_cleared</a>
parameter controls sender notification when the delay clears up.



To enable this feature, specify a non-zero time value (an integral
value plus an optional one-letter suffix that specifies the time
unit).



Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours).



See also: <a href="postconf.5.html#delay_notice_recipient">delay_notice_recipient</a>, <a href="postconf.5.html#notify_classes">notify_classes</a>, <a href="postconf.5.html#confirm_delay_cleared">confirm_delay_cleared</a>.


</DD>

<DT><a name="deliver_lock_attempts">deliver_lock_attempts</a>
(default: 20)</DT><DD>


The maximal number of attempts to acquire an exclusive lock on a
mailbox file or <a href="bounce.8.html">bounce(8)</a> logfile.


</DD>

<DT><a name="deliver_lock_delay">deliver_lock_delay</a>
(default: 1s)</DT><DD>


The time between attempts to acquire an exclusive lock on a mailbox
file or <a href="bounce.8.html">bounce(8)</a> logfile.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="destination_concurrency_feedback_debug">destination_concurrency_feedback_debug</a>
(default: no)</DT><DD>

 Make the queue manager's feedback algorithm verbose for performance
analysis purposes. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="detect_8bit_encoding_header">detect_8bit_encoding_header</a>
(default: yes)</DT><DD>

 Automatically detect 8BITMIME body content by looking at
Content-Transfer-Encoding: message headers; historically, this
behavior was hard-coded to be "always on". 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="disable_dns_lookups">disable_dns_lookups</a>
(default: no)</DT><DD>


Disable DNS lookups in the Postfix SMTP and LMTP clients. When
disabled, hosts are looked up with the getaddrinfo() system
library routine which normally also looks in /etc/hosts. As of
Postfix 2.11, this parameter is deprecated; use <a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>
instead.



DNS lookups are enabled by default.


</DD>

<DT><a name="disable_mime_input_processing">disable_mime_input_processing</a>
(default: no)</DT><DD>


Turn off MIME processing while receiving mail. This means that no
special treatment is given to Content-Type: message headers, and
that all text after the initial message headers is considered to
be part of the message body.



This feature is available in Postfix 2.0 and later.



Mime input processing is enabled by default, and is needed in order
to recognize MIME headers in message content.


</DD>

<DT><a name="disable_mime_output_conversion">disable_mime_output_conversion</a>
(default: no)</DT><DD>


Disable the conversion of 8BITMIME format to 7BIT format. Mime
output conversion is needed when the destination does not advertise
8BITMIME support.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="disable_verp_bounces">disable_verp_bounces</a>
(default: no)</DT><DD>


Disable sending one bounce report per recipient.



The default, one per recipient, is what ezmlm needs.



This feature is available in Postfix 1.1 and later.


</DD>

<DT><a name="disable_vrfy_command">disable_vrfy_command</a>
(default: no)</DT><DD>


Disable the SMTP VRFY command. This stops some techniques used to
harvest email addresses.



Example:


<pre>
<a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a> = no
</pre>

</DD>

<DT><a name="dns_ncache_ttl_fix_enable">dns_ncache_ttl_fix_enable</a>
(default: no)</DT><DD>

 Enable a workaround for future libc incompatibility. The Postfix
implementation of <a href="https://tools.ietf.org/html/rfc2308">RFC 2308</a> negative reply caching relies on the
promise that res_query() and res_search() invoke res_send(), which
returns the server response in an application buffer even if the
requested record does not exist. If this promise is broken, specify
"yes" to enable a workaround for DNS reputation lookups. 


This feature is available in Postfix 3.1 and later.


</DD>

<DT><a name="dnsblog_reply_delay">dnsblog_reply_delay</a>
(default: 0s)</DT><DD>

 A debugging aid to artificially delay DNS responses. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="dnsblog_service_name">dnsblog_service_name</a>
(default: dnsblog)</DT><DD>

 The name of the <a href="dnsblog.8.html">dnsblog(8)</a> service entry in <a href="master.5.html">master.cf</a>. This
service performs DNS allow/denylist lookups. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="dnssec_probe">dnssec_probe</a>
(default: ns:.)</DT><DD>

 The DNS query type (default: "ns") and DNS query name (default:
".") that Postfix may use to determine whether DNSSEC validation
is available.


 Background: DNSSEC validation is needed for Postfix DANE support;
this ensures that Postfix receives TLSA records with secure TLS
server certificate info. When DNSSEC validation is unavailable,
mail deliveries using opportunistic DANE will not be protected
by server certificate info in TLSA records, and mail deliveries
using mandatory DANE will not be made at all. 

 By default, a Postfix process will send a DNSSEC probe after
1) the process made a DNS query that requested DNSSEC validation,
2) the process did not receive a DNSSEC validated response to this
query or to an earlier query, and 3) the process did not already
send a DNSSEC probe. 

 When the DNSSEC probe has no response, or when the response is
not DNSSEC validated, Postfix logs a warning that DNSSEC validation
may be unavailable. 

 Example: 

<pre>
warning: DNSSEC validation may be unavailable
warning: reason: <a href="postconf.5.html#dnssec_probe">dnssec_probe</a> 'ns:.' received a response that is not DNSSEC validated
warning: reason: <a href="postconf.5.html#dnssec_probe">dnssec_probe</a> 'ns:.' received no response: Server failure
</pre>

 Possible reasons why DNSSEC validation may be unavailable: 

<ul>

<li> The local /etc/resolv.conf file specifies a DNS resolver that
does not validate DNSSEC signatures (that's
$<a href="postconf.5.html#queue_directory">queue_directory</a>/etc/resolv.conf when a Postfix daemon runs in a
chroot jail).

<li> The local system library does not pass on the "DNSSEC validated"
bit to Postfix, or Postfix does not know how to ask the library to
do that.

</ul>

 By default, the DNSSEC probe asks for the DNS root zone NS
records, because resolvers should always have that information
cached. If Postfix runs on a network where the DNS root zone is not
reachable, specify a different probe, or specify an empty <a href="postconf.5.html#dnssec_probe">dnssec_probe</a>
value to disable the feature. 

 This feature is available in Postfix 3.6 and later. It was backported
to Postfix versions 3.5.9, 3.4.19, 3.3.16. 3.2.21. 

</DD>

<DT><a name="domain_to_ascii">domain_to_ascii</a>
(default: no default)</DT><DD>

 A function that returns the ASCII representation of its domain
name argument. If the argument contains only (7-bit) ASCII characters
(A-label form), then <a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{} will return the same value.
If the argument contains a valid non-ASCII domain name (U-label
form), then <a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{} will return the corresponding Punycode
(A-label form). Other argument values may result in a program
start-up error. 

 Examples: 

<ul>

<li> The examples below assume that <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a>
contains the default setting: 
<pre>
<a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> = <a href="DATABASE_README.html#types">inline</a>:{
 { ${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic },
 { .${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic },
 ...
</pre>

<li> Example 1: when <a href="postconf.5.html#mydomain">mydomain</a> contains only ASCII characters,
<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{} returns the same value. 
<pre>
# postconf -o '<a href="postconf.5.html#mydomain">mydomain</a>=foo.example' -x <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a>
<a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> = <a href="DATABASE_README.html#types">inline</a>:{
 { foo.example = opportunistic },
 { .foo.example = opportunistic },
 ...
</pre>

<li> Example 2: when <a href="postconf.5.html#mydomain">mydomain</a> contains non-ASCII characters,
<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{} returns the Punycode representation. 
<pre>
# postconf -o '<a href="postconf.5.html#mydomain">mydomain</a>=π.example' -x <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a>
<a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> = <a href="DATABASE_README.html#types">inline</a>:{
 { xn--1xa.example = opportunistic },
 { .xn--1xa.example = opportunistic },
 ...
</pre>

</ul>

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="dont_remove">dont_remove</a>
(default: 0)</DT><DD>


Don't remove queue files and save them to the "saved" mail queue.
This is a debugging aid. To inspect the envelope information and
content of a Postfix queue file, use the <a href="postcat.1.html">postcat(1)</a> command.


</DD>

<DT><a name="double_bounce_sender">double_bounce_sender</a>
(default: double-bounce)</DT><DD>

 The sender address of postmaster notifications that are generated
by the mail system. All mail to this address is silently discarded,
in order to terminate mail bounce loops. 

</DD>

<DT><a name="duplicate_filter_limit">duplicate_filter_limit</a>
(default: 1000)</DT><DD>

 The maximal number of addresses remembered by the address
duplicate filter for <a href="aliases.5.html">aliases(5)</a> or <a href="virtual.5.html">virtual(5)</a> alias expansion, or
for <a href="showq.8.html">showq(8)</a> queue displays. 

</DD>

<DT><a name="empty_address_default_transport_maps_lookup_key">empty_address_default_transport_maps_lookup_key</a>
(default: <>)</DT><DD>

 The <a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> search string that
will be used instead of the null sender address. 

 This feature is available in Postfix 2.7 and later. 

</DD>

<DT><a name="empty_address_local_login_sender_maps_lookup_key">empty_address_local_login_sender_maps_lookup_key</a>
(default: <>)</DT><DD>


The lookup key to be used in <a href="postconf.5.html#local_login_sender_maps">local_login_sender_maps</a> tables, instead
of the null sender address.


 This feature is available in Postfix 3.6 and later. 

</DD>

<DT><a name="empty_address_recipient">empty_address_recipient</a>
(default: MAILER-DAEMON)</DT><DD>


The recipient of mail addressed to the null address. Postfix does
not accept such addresses in SMTP commands, but they may still be
created locally as the result of configuration or software error.


</DD>

<DT><a name="empty_address_relayhost_maps_lookup_key">empty_address_relayhost_maps_lookup_key</a>
(default: <>)</DT><DD>

 The <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> search string that will be
used instead of the null sender address. 

 This feature is available in Postfix 2.5 and later. With
earlier versions, <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> lookups were
skipped for the null sender address. 

</DD>

<DT><a name="enable_errors_to">enable_errors_to</a>
(default: no)</DT><DD>

 Report mail delivery errors to the address specified with the
non-standard Errors-To: message header, instead of the envelope
sender address (this feature is removed with Postfix version 2.2, is
turned off by default with Postfix version 2.1, and is always turned on
with older Postfix versions). 

</DD>

<DT><a name="enable_idna2003_compatibility">enable_idna2003_compatibility</a>
(default: no)</DT><DD>

 Enable 'transitional' compatibility between IDNA2003 and IDNA2008,
when converting UTF-8 domain names to/from the ASCII form that is
used for DNS lookups. Specify "yes" for compatibility with Postfix
≤ 3.1 (not recommended). This affects the conversion of domain
names that contain for example the German sz and the Greek sigma.
See <a href="https://unicode.org/cldr/utility/idna.jsp">https://unicode.org/cldr/utility/idna.jsp</a> for more examples.


 This feature is available in Postfix 3.2 and later. 

</DD>

<DT><a name="enable_long_queue_ids">enable_long_queue_ids</a>
(default: no)</DT><DD>

 Enable long, non-repeating, queue IDs (queue file names). The
benefit of non-repeating names is simpler logfile analysis and
easier queue migration (there is no need to run "postsuper" to
change queue file names that don't match their message file inode
number). 

 Note: see below for how to convert long queue file names to
Postfix ≤ 2.8. 

 Changing the parameter value to "yes" has the following effects:


<ul>

<li> Existing queue file names are not affected. 

<li> New queue files are created with names such as 3Pt2mN2VXxznjll.
These are encoded in a 52-character alphabet that contains digits
(0-9), upper-case letters (B-Z) and lower-case letters (b-z). For
safety reasons the vowels (AEIOUaeiou) are excluded from the alphabet.
The name format is: 6 or more characters for the time in seconds,
4 characters for the time in microseconds, the 'z'; the remainder
is the file inode number encoded in the first 51 characters of the
52-character alphabet. 

<li> New messages have a Message-ID header with
queueID@<a href="postconf.5.html#myhostname">myhostname</a>. 

<li> The mailq (postqueue -p) output has a wider Queue ID column.
The number of whitespace-separated fields is not changed. 

<li> The <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> algorithm uses the first characters
of the queue file creation time in microseconds, after conversion
into hexadecimal representation. This produces the same queue hashing
behavior as if the queue file name was created with "<a href="postconf.5.html#enable_long_queue_ids">enable_long_queue_ids</a>
= no". 

</ul>

 Changing the parameter value to "no" has the following effects:


<ul>

<li> Existing long queue file names are renamed to the short
form (while running "postfix reload" or "postsuper"). 

<li> New queue files are created with names such as C3CD21F3E90
from a hexadecimal alphabet that contains digits (0-9) and upper-case
letters (A-F). The name format is: 5 characters for the time in
microseconds; the remainder is the file inode number. 

<li> New messages have a Message-ID header with
YYYYMMDDHHMMSS.queueid@<a href="postconf.5.html#myhostname">myhostname</a>, where
YYYYMMDDHHMMSS are the year, month, day, hour, minute and
second.

<li> The mailq (postqueue -p) output has the same format as
with Postfix ≤ 2.8. 

<li> The <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> algorithm uses the first characters
of the queue file name, with the hexadecimal representation of the
file creation time in microseconds. 

</ul>

 Before migration to Postfix ≤ 2.8, the following commands
are required to convert long queue file names into short names: 

<pre>
# postfix stop
# postconf <a href="postconf.5.html#enable_long_queue_ids">enable_long_queue_ids</a>=no
# postsuper
</pre>

 Repeat the postsuper command until it reports no more queue file
name changes. 

 This feature is available in Postfix 2.9 and later. 

</DD>

<DT><a name="enable_original_recipient">enable_original_recipient</a>
(default: yes)</DT><DD>

 Enable support for the original recipient address after an
address is rewritten to a different address (for example with
aliasing or with canonical mapping). 

 The original recipient address is used as follows: 

<dl>

<dt> Final delivery </dt> <dd> With "<a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a> =
yes", the original recipient address is stored in the X-Original-To
message header. This header may be used to distinguish between
different recipients that share the same mailbox. </dd>

<dt> Recipient deduplication </dt> <dd> With "<a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a>
= yes", the <a href="cleanup.8.html">cleanup(8)</a> daemon performs duplicate recipient elimination
based on the content of (original recipient, maybe-rewritten
recipient) pairs. Otherwise, the <a href="cleanup.8.html">cleanup(8)</a> daemon performs duplicate
recipient elimination based only on the maybe-rewritten recipient
address. </dd>

</dl>

 Note: with Postfix ≤ 3.2 the "setting <a href="postconf.5.html#enable_original_recipient">enable_original_recipient</a>
= no" breaks address verification for addresses that are
aliased or otherwise rewritten (Postfix is unable to store the
address verification result under the original probe destination
address; instead, it can store the result only under the rewritten
address). 

 This feature is available in Postfix 2.1 and later. Postfix
version 2.0 behaves as if this parameter is always set to yes.
Postfix versions before 2.0 have no support for the original recipient
address. 

</DD>

<DT><a name="enable_threaded_bounces">enable_threaded_bounces</a>
(default: no)</DT><DD>

 Enable non-delivery, success, and delay notifications that link
to the original message by including a References: and In-Reply-To:
header with the original Message-ID value. There are advantages and
disadvantages to consider. 

<dl>

<dt> advantage </dt> <dd> This allows mail readers to present
a delivery status notification in the same email thread as the original
message. </dd>

<dt> disadvantage </dt> <dd> This makes it easy for users to
mistakenly delete the whole email thread (all related messages),
instead of deleting only the non-delivery notification. </dd>

</dl>

 This feature is available in Postfix 3.6 and later. 

</DD>

<DT><a name="error_notice_recipient">error_notice_recipient</a>
(default: postmaster)</DT><DD>

 The recipient of postmaster notifications about mail delivery
problems that are caused by policy, resource, software or protocol
errors. These notifications are enabled with the <a href="postconf.5.html#notify_classes">notify_classes</a>
parameter. 

</DD>

<DT><a name="error_service_name">error_service_name</a>
(default: error)</DT><DD>


The name of the <a href="error.8.html">error(8)</a> pseudo delivery agent. This service always
returns mail as undeliverable.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="execution_directory_expansion_filter">execution_directory_expansion_filter</a>
(default: see "postconf -d" output)</DT><DD>

 Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows
in $name expansions of $<a href="postconf.5.html#command_execution_directory">command_execution_directory</a>. Characters
outside the allowed set are replaced by underscores. 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="expand_owner_alias">expand_owner_alias</a>
(default: no)</DT><DD>


When delivering to an alias "aliasname" that has an
"owner-aliasname" companion alias, set the envelope sender
address to the expansion of the "owner-aliasname" alias.
Normally, Postfix sets the envelope sender address to the name of
the "owner-aliasname" alias.


</DD>

<DT><a name="export_environment">export_environment</a>
(default: see "postconf -d" output)</DT><DD>


The list of environment variables that a Postfix process will export
to non-Postfix processes. The TZ variable is needed for sane
time keeping on System-V-ish systems.



Specify a list of names and/or name=value pairs, separated by
whitespace or comma. Specify "{ name=value }" to protect whitespace
or comma in parameter values (whitespace after the opening "{" and
before the closing "}"
is ignored). The form name=value is supported with Postfix version
2.1 and later; the use of {} is supported with Postfix 3.0 and
later. 


Example:


<pre>
<a href="postconf.5.html#export_environment">export_environment</a> = TZ PATH=/bin:/usr/bin
</pre>

</DD>

<DT><a name="extract_recipient_limit">extract_recipient_limit</a>
(default: 10240)</DT><DD>


The maximal number of recipient addresses that Postfix will extract
from message headers when mail is submitted with "sendmail -t".



This feature was removed in Postfix version 2.1.


</DD>

<DT><a name="fallback_relay">fallback_relay</a>
(default: empty)</DT><DD>


Optional list of relay hosts for SMTP destinations that can't be
found or that are unreachable. With Postfix 2.3 this parameter
is renamed to <a href="postconf.5.html#smtp_fallback_relay">smtp_fallback_relay</a>. 


By default, mail is returned to the sender when a destination is
not found, and delivery is deferred when a destination is unreachable.


 The fallback relays must be SMTP destinations. Specify a domain,
host, host:port, [host]:port, [address] or [address]:port; the form
[host] turns off MX lookups. If you specify multiple SMTP
destinations, Postfix will try them in the specified order. 

 Note: before Postfix 2.2, do not use the <a href="postconf.5.html#fallback_relay">fallback_relay</a> feature
when relaying mail
for a backup or primary MX domain. Mail would loop between the
Postfix MX host and the <a href="postconf.5.html#fallback_relay">fallback_relay</a> host when the final destination
is unavailable. 

<ul>

<li> In <a href="postconf.5.html">main.cf</a> specify "<a href="postconf.5.html#relay_transport">relay_transport</a> = relay",

<li> In <a href="master.5.html">master.cf</a> specify "-o <a href="postconf.5.html#fallback_relay">fallback_relay</a> =" (i.e., empty) at
the end of the <tt>relay</tt> entry.

<li> In transport maps, specify "relay:nexthop..."
as the right-hand side for backup or primary MX domain entries.

</ul>

 Postfix version 2.2 and later will not use the <a href="postconf.5.html#fallback_relay">fallback_relay</a> feature
for destinations that it is MX host for.


</DD>

<DT><a name="fallback_transport">fallback_transport</a>
(default: empty)</DT><DD>


Optional message delivery transport that the <a href="local.8.html">local(8)</a> delivery
agent should use for names that are not found in the <a href="aliases.5.html">aliases(5)</a>
or UNIX password database.


 The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. 

</DD>

<DT><a name="fallback_transport_maps">fallback_transport_maps</a>
(default: empty)</DT><DD>

 Optional lookup tables with per-recipient message delivery
transports for recipients that the <a href="local.8.html">local(8)</a> delivery agent could
not find in the <a href="aliases.5.html">aliases(5)</a> or UNIX password database. 

 The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. 

 For safety reasons, this feature does not allow $number
substitutions in regular expression maps. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="fast_flush_domains">fast_flush_domains</a>
(default: $<a href="postconf.5.html#relay_domains">relay_domains</a>)</DT><DD>


Optional list of destinations that are eligible for per-destination
logfiles with mail that is queued to those destinations.



By default, Postfix maintains "fast flush" logfiles only for
destinations that the Postfix SMTP server is willing to relay to
(i.e. the default is: "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a> = $<a href="postconf.5.html#relay_domains">relay_domains</a>"; see
the <a href="postconf.5.html#relay_domains">relay_domains</a> parameter in the <a href="postconf.5.html">postconf(5)</a> manual).


 Specify a list of hosts or domains, "/file/name" patterns or
"<a href="DATABASE_README.html">type:table</a>" lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
lookup table is matched when the domain or its parent domain appears
as lookup key. 

 Pattern matching of domain names is controlled by the presence
or absence of "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
parameter value. 


Specify "<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a> =" (i.e., empty) to disable the feature
altogether.


</DD>

<DT><a name="fast_flush_purge_time">fast_flush_purge_time</a>
(default: 7d)</DT><DD>


The time after which an empty per-destination "fast flush" logfile
is deleted.



You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks. The default time unit is days.


</DD>

<DT><a name="fast_flush_refresh_time">fast_flush_refresh_time</a>
(default: 12h)</DT><DD>


The time after which a non-empty but unread per-destination "fast
flush" logfile needs to be refreshed. The contents of a logfile
are refreshed by requesting delivery of all messages listed in the
logfile.



You can specify the time as a number, or as a number followed by
a letter that indicates the time unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks. The default time unit is hours.


</DD>

<DT><a name="fault_injection_code">fault_injection_code</a>
(default: 0)</DT><DD>


Force specific internal tests to fail, to test the handling of
errors that are difficult to reproduce otherwise.


</DD>

<DT><a name="flush_service_name">flush_service_name</a>
(default: flush)</DT><DD>


The name of the <a href="flush.8.html">flush(8)</a> service. This service maintains per-destination
logfiles with the queue file names of mail that is queued for those
destinations.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="force_mime_input_conversion">force_mime_input_conversion</a>
(default: no)</DT><DD>

 Convert body content that claims to be 8-bit into quoted-printable,
before <a href="postconf.5.html#header_checks">header_checks</a>, <a href="postconf.5.html#body_checks">body_checks</a>, Milters, and before after-queue
content filters. This feature does not affect messages that are
sent into <a href="postconf.5.html#smtpd_proxy_filter">smtpd_proxy_filter</a>. 

 The typical use case is an MTA that applies this conversion
before signing outbound messages, so that the signatures will remain
valid when a message is later delivered to an MTA that does not
announce 8BITMIME support, or when a message line exceeds the SMTP
length limit. 

 This feature is available in Postfix ≥ 3.9. 

</DD>

<DT><a name="fork_attempts">fork_attempts</a>
(default: 5)</DT><DD>

 The maximal number of attempts to fork() a child process. 

</DD>

<DT><a name="fork_delay">fork_delay</a>
(default: 1s)</DT><DD>

 The delay between attempts to fork() a child process. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="forward_expansion_filter">forward_expansion_filter</a>
(default: see "postconf -d" output)</DT><DD>


Restrict the characters that the <a href="local.8.html">local(8)</a> delivery agent allows in
$name expansions of $<a href="postconf.5.html#forward_path">forward_path</a>. Characters outside the
allowed set are replaced by underscores.


</DD>

<DT><a name="forward_path">forward_path</a>
(default: see "postconf -d" output)</DT><DD>

 The <a href="local.8.html">local(8)</a> delivery agent search list for finding a .forward
file with user-specified delivery methods. The first file that is
found is used. 

 The <a href="postconf.5.html#forward_path">forward_path</a> value is not subject to Postfix configuration
parameter $name expansion. Instead, the following $name expansions
are done on <a href="postconf.5.html#forward_path">forward_path</a> before the search actually happens.
The result of $name expansion is
filtered with the character set that is specified with the
<a href="postconf.5.html#forward_expansion_filter">forward_expansion_filter</a> parameter. 

<dl>

<dt>$user</dt>

<dd>The recipient's username. </dd>

<dt>$shell</dt>

<dd>The recipient's login shell pathname. </dd>

<dt>$home</dt>

<dd>The recipient's home directory. </dd>

<dt>$recipient</dt>

<dd>The full recipient address. </dd>

<dt>$extension</dt>

<dd>The optional recipient address extension. </dd>

<dt>$domain</dt>

<dd>The recipient domain. </dd>

<dt>$local</dt>

<dd>The entire recipient localpart. </dd>

<dt>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></dt>

<dd>The address extension delimiter that was found in the recipient
address (Postfix 2.11 and later), or the 'first' delimiter specified
with the system-wide recipient address extension delimiter (Postfix
3.5.22, 3.6.12, 3.7.8, 3.8.3 and later). Historically, this was
always the system-wide recipient
address extension delimiter (Postfix 2.10 and earlier). </dd>

<dt>${name?value}</dt>

<dt>${name?{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is non-empty. </dd>

<dt>${name:value}</dt>

<dt>${name:{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is empty. </dd>

<dt>${name?{value1}:{value2}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value1 when $name is non-empty,
value2 otherwise. </dd>

</dl>


Instead of $name you can also specify ${name} or $(name).



Examples:


<pre>
<a href="postconf.5.html#forward_path">forward_path</a> = /var/forward/$user
<a href="postconf.5.html#forward_path">forward_path</a> =
 /var/forward/$user/.forward$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>$extension,
 /var/forward/$user/.forward
</pre>

</DD>

<DT><a name="frozen_delivered_to">frozen_delivered_to</a>
(default: yes)</DT><DD>

 Update the <a href="local.8.html">local(8)</a> delivery agent's idea of the Delivered-To:
address (see <a href="postconf.5.html#prepend_delivered_header">prepend_delivered_header</a>) only once, at the start of
a delivery attempt; do not update the Delivered-To: address while
expanding aliases or .forward files. 

 This feature is available in Postfix 2.3 and later. With older
Postfix releases, the behavior is as if this parameter is set to
"no". The old setting can be expensive with deeply nested aliases
or .forward files. When an alias or .forward file changes the
Delivered-To: address, it ties up one queue file and one cleanup
process instance while mail is being forwarded. 

</DD>

<DT><a name="full_name_encoding_charset">full_name_encoding_charset</a>
(default: utf-8)</DT><DD>

 The character set name (also called "charset") that Postfix
will output when it automatically generates an <a href="https://tools.ietf.org/html/rfc2047">RFC 2047</a> encoded
full name. Encoding non-ASCII full names can avoid the need to use
SMTPUTF8, and therefore can avoid incompatibility with sites that
do not support SMTPUTF8. 

 The encoded names look like "=?charset?q?gibberish?=" with
quoted-printable encoding, or "=?charset?b?gibberish?=" with base64
encoding. Postfix uses quoted-printable encoding for a full name
that is short or mostly printable ASCII, and uses base64 otherwise.


 Background: when a message without a From: header is submitted
with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command, the Postfix <a href="cleanup.8.html">cleanup(8)</a> daemon
will add a From: header and will try to use the sender's full name
specified with the Postfix <a href="sendmail.1.html">sendmail(1)</a> "-F" option, with the Postfix
<a href="sendmail.1.html">sendmail(1)</a> "NAME" environment variable, or with the GECOS field
in the UNIX password database. In the latter case, Postfix will
replace the "&" character with the login name, with a lowercase
ASCII first character converted to uppercase. 

 NOTE: Postfix does not convert between character sets. The
<a href="postconf.5.html#full_name_encoding_charset">full_name_encoding_charset</a> parameter specifies the character set
of the full name in the Postfix sendmail "-F" option, in the Postfix
sendmail "NAME" environment variable, or in the GECOS field of the
UNIX password database. The parameter value is also part of the
encoded full name, and informs a Mail User Agent how to display the
decoded gibberish. 

 Specify a valid character set name such as "utf-8" or "iso-8859-1
(specify the latter for full names that use the Latin1 encoding).
The character set name is case insensitive. When a character set
name violates <a href="https://tools.ietf.org/html/rfc2047">RFC 2047</a> syntax, Postfix will log a warning and will
skip the full name. 

 This feature is available in Postfix ≥ 3.10. 

</DD>

<DT><a name="hash_queue_depth">hash_queue_depth</a>
(default: 1)</DT><DD>


The number of subdirectory levels for queue directories listed with
the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> parameter. Queue hashing is implemented by
creating one or more levels of directories with one-character names.
Originally, these directory names were equal to the first characters
of the queue file name, with the hexadecimal representation of the
file creation time in microseconds. 

 With long queue file names, queue hashing produces the same
results as with short names. The file creation time in microseconds
is converted into hexadecimal form before the result is used for
queue hashing. The base 16 encoding gives finer control over the
number of subdirectories than is possible with the base 52 encoding
of long queue file names. 


After changing the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> or <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> parameter,
execute the command "postfix reload".


</DD>

<DT><a name="hash_queue_names">hash_queue_names</a>
(default: deferred, defer)</DT><DD>


The names of queue directories that are split across multiple
subdirectory levels.


 Before Postfix version 2.2, the default list of hashed queues
was significantly larger. Claims about improvements in file system
technology suggest that hashing of the <a href="QSHAPE_README.html#incoming_queue">incoming</a> and <a href="QSHAPE_README.html#active_queue">active queues</a>
is no longer needed. Fewer hashed directories speed up the time
needed to restart Postfix. 


After changing the <a href="postconf.5.html#hash_queue_names">hash_queue_names</a> or <a href="postconf.5.html#hash_queue_depth">hash_queue_depth</a> parameter,
execute the command "postfix reload".


</DD>

<DT><a name="header_address_token_limit">header_address_token_limit</a>
(default: 10240)</DT><DD>


The maximal number of address tokens are allowed in an address
message header. Information that exceeds the limit is discarded.
The limit is enforced by the <a href="cleanup.8.html">cleanup(8)</a> server.


</DD>

<DT><a name="header_checks">header_checks</a>
(default: empty)</DT><DD>


Optional lookup tables for content inspection of primary non-MIME
message headers, as specified in the <a href="header_checks.5.html">header_checks(5)</a> manual page.


</DD>

<DT><a name="header_from_format">header_from_format</a>
(default: standard)</DT><DD>

 The format of the Postfix-generated From: header. This
setting affects the appearance of 'full name' information when a
local program such as /bin/mail submits a message without a From:
header through the Postfix <a href="sendmail.1.html">sendmail(1)</a> command. 

 Specify one of the following: 

<dl>

<dt>standard (default)</dt> <dd> Produce a header formatted
as "From: name <address>".
This is the default as of Postfix 3.3.</dd>

<dt>obsolete</dt> <dd>Produce a header formatted as "From:
address (name)". This is the behavior
prior to Postfix 3.3. </dd>

</dl>

 Notes: 

<ul>

<li> Postfix generates the format "From: address"
when name information is unavailable or the envelope sender
address is empty. This is the same behavior as prior to Postfix
3.3. 

<li> In the standard form, the name will be quoted
if it contains specials as defined in <a href="https://tools.ietf.org/html/rfc5322">RFC 5322</a>, or the "!%"
address operators. 

<li> The Postfix <a href="sendmail.1.html">sendmail(1)</a> command gets name information
from the -F command-line option, from the NAME
environment variable, or from the UNIX password file. 

</ul>

 This feature is available in Postfix 3.3 and later. 

</DD>

<DT><a name="header_size_limit">header_size_limit</a>
(default: 102400)</DT><DD>


The maximal amount of memory in bytes for storing a message header.
If a header is larger, the excess is discarded. The limit is
enforced by the <a href="cleanup.8.html">cleanup(8)</a> server.


</DD>

<DT><a name="helpful_warnings">helpful_warnings</a>
(default: yes)</DT><DD>


Log warnings about problematic configuration settings, and provide
helpful suggestions.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="home_mailbox">home_mailbox</a>
(default: empty)</DT><DD>


Optional pathname of a mailbox file relative to a <a href="local.8.html">local(8)</a> user's
home directory.



Specify a pathname ending in "/" for qmail-style delivery.


 The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. 


Examples:


<pre>
<a href="postconf.5.html#home_mailbox">home_mailbox</a> = Mailbox
<a href="postconf.5.html#home_mailbox">home_mailbox</a> = Maildir/
</pre>

</DD>

<DT><a name="hopcount_limit">hopcount_limit</a>
(default: 50)</DT><DD>


The maximal number of Received: message headers that is allowed
in the primary message headers. A message that exceeds the limit
is bounced, in order to stop a mailer loop.


</DD>

<DT><a name="html_directory">html_directory</a>
(default: see "postconf -d" output)</DT><DD>


The location of Postfix HTML files that describe how to build,
configure or operate a specific Postfix subsystem or feature.


</DD>

<DT><a name="ignore_mx_lookup_error">ignore_mx_lookup_error</a>
(default: no)</DT><DD>

 Ignore DNS MX lookups that produce no response. By default,
the Postfix SMTP client defers delivery and tries again after some
delay. This behavior is required by the SMTP standard. 


Specify "<a href="postconf.5.html#ignore_mx_lookup_error">ignore_mx_lookup_error</a> = yes" to force a DNS A record
lookup instead. This violates the SMTP standard and can result in
mis-delivery of mail.


</DD>

<DT><a name="ignore_srv_lookup_error">ignore_srv_lookup_error</a>
(default: no)</DT><DD>

 When SRV record lookup fails, fall back to MX or IP address
lookup as if SRV record lookup was not enabled. 

 This feature is available in Postfix 3.8 and later. 

</DD>

<DT><a name="import_environment">import_environment</a>
(default: see "postconf -d" output)</DT><DD>

 The list of environment variables that a privileged Postfix
process will import from a non-Postfix parent process, or name=value
environment overrides. Unprivileged utilities will enforce the
name=value overrides, but otherwise will not change their process
environment. Examples of relevant environment variables: 

<dl>

<dt>TZ</dt>

<dd>May be needed for sane time keeping on most System-V-ish systems.
</dd>

<dt>DISPLAY</dt>

<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>

<dt>XAUTHORITY</dt>

<dd>Needed for debugging Postfix daemons with an X-windows debugger. </dd>

<dt>MAIL_CONFIG</dt>

<dd>Needed to make "postfix -c" work. </dd>

<dt>POSTLOG_HOSTNAME</dt>

<dd>Needed to make "<a href="postconf.5.html#maillog_file">maillog_file</a>" work during daemon
process initialization. </dd>

<dt>POSTLOG_SERVICE</dt>

<dd>Needed to make "<a href="postconf.5.html#maillog_file">maillog_file</a>" work during daemon
process initialization. </dd>

<dt>XDG_RUNTIME_DIR</dt>

<dd>Needed for debugging Postfix daemons with an XDG-style debugger.
</dd>

</dl>

 Specify a list of names and/or name=value pairs, separated by
whitespace or comma. Specify "{ name=value }" to protect whitespace
or comma in environment variable values (whitespace after the opening "{" and
before the closing "}"
is ignored). The form name=value is supported with Postfix version
2.1 and later; the use of {} is supported with Postfix 3.0 and
later. 

</DD>

<DT><a name="in_flow_delay">in_flow_delay</a>
(default: 1s)</DT><DD>

 Time to pause before accepting a new message, when the message
arrival rate exceeds the message delivery rate. This feature is
turned on by default (it's disabled on SCO UNIX due to an SCO bug).



With the default 100 Postfix SMTP server process limit, "<a href="postconf.5.html#in_flow_delay">in_flow_delay</a>
= 1s" limits the mail inflow to 100 messages per second above the
number of messages delivered per second.



Specify 0 to disable the feature. Valid delays are 0..10.


</DD>

<DT><a name="inet_interfaces">inet_interfaces</a>
(default: all)</DT><DD>

 The local network interface addresses that this mail system
receives mail on. Specify "all" to receive mail on all network
interfaces (default), "loopback-only" to receive mail on loopback
network interfaces only (Postfix version 2.2 and later), or zero
or more IPv4 or IPv6 addresses (IPv6 is supported in Postfix version
2.2 and later). The parameter also controls whether Postfix will
accept mail for <tt>user@[ip.address]</tt>, and prevents Postfix
from delivering mail to a host that has equal or larger MX preference.
Specify an empty value if Postfix does not receive mail over the
network, or if all network listeners have an explicit IP address
in <a href="master.5.html">master.cf</a>. 


Note 1: you need to stop and start Postfix when this parameter changes.


 Note 2: address information may be enclosed inside <tt>[]</tt>,
but this form is not required here. 

 When <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> and/or <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> are not
specified, the <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> setting may constrain the source IP
address for an outbound SMTP or LMTP connection as described below.


 The following text is specific to SMTP and IPv4. The same
reasoning applies to the IPv6 protocol, and to the Postfix LMTP
client. To disable IPv4 or IPv6 support in the Postfix SMTP and
LMTP client, use <a href="postconf.5.html#inet_protocols">inet_protocols</a>. 

<ul>

<li> When <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies one IPv4 address, and that
is not a loopback address, the Postfix SMTP client uses that as the
source address for outbound IPv4 connections. 

<li> Otherwise, the Postfix SMTP client does not constrain the
source IPv4 address, and connects using a system-chosen source IPv4
address. This includes the cases where <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> is empty,
where it specifies all, or where it contains no IPv4 address,
one IPv4 address that is a loopback address, or multiple IPv4
addresses. 

</ul>

 A Postfix SMTP client may fail to reach some remote SMTP servers
when the client source IP address is constrained explicitly with
<a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> or <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a>, or implicitly with
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>. This can happen when Postfix runs on a multi-homed
system such as a firewall, the Postfix SMTP source client IP address
is constrained to one specific network interface, and the remote
SMTP server must be reached through a different interface. Setting
<a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> to 0.0.0.0 avoids the potential problem for IPv4,
and setting <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> to :: solves the problem for IPv6.



A better solution for multi-homed systems is to leave <a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
at the default value and instead use explicit IP addresses in
the <a href="master.5.html">master.cf</a> SMTP server definitions. This preserves the Postfix
SMTP client's
loop detection, by ensuring that each side of the firewall knows that the
other IP address is still the same host. Setting $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> to a
single IPv4 and/or IPV6 address is primarily useful with virtual
hosting of domains on
secondary IP addresses, when each IP address serves a different domain
(and has a different $<a href="postconf.5.html#myhostname">myhostname</a> setting). 


See also the <a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> parameter, for network addresses that
are forwarded to Postfix by way of a proxy or address translator.



Examples:


<pre>
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = all (DEFAULT)
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = loopback-only (Postfix version 2.2 and later)
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 127.0.0.1
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 127.0.0.1, [::1] (Postfix version 2.2 and later)
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> = 192.168.1.2, 127.0.0.1
</pre>

</DD>

<DT><a name="inet_protocols">inet_protocols</a>
(default: see 'postconf -d' output)</DT><DD>

 The Internet protocols Postfix will attempt to use when making
or accepting connections. Specify one or more of "ipv4"
or "ipv6", separated by whitespace or commas. The form
"all" is equivalent to "ipv4, ipv6" or "ipv4", depending
on whether the operating system implements IPv6. 

 With Postfix 2.8 and earlier the default is "ipv4". For backwards
compatibility with these releases, the Postfix 2.9 and later upgrade
procedure appends an explicit "<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4" setting to
<a href="postconf.5.html">main.cf</a> when no explicit setting is present. This compatibility
workaround will be phased out as IPv6 deployment becomes more common.


 This feature is available in Postfix 2.2 and later. 

 Note: you MUST stop and start Postfix after changing this
parameter. 

 On systems that pre-date IPV6_V6ONLY support (<a href="https://tools.ietf.org/html/rfc3493">RFC 3493</a>), an
IPv6 server will also accept IPv4 connections, even when IPv4 is
turned off with the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter. On systems with
IPV6_V6ONLY support, Postfix will use separate server sockets for
IPv6 and IPv4, and each will accept only connections for the
corresponding protocol. 

 When IPv4 support is enabled via the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter,
Postfix will look up DNS type A records, and will convert
IPv4-in-IPv6 client IP addresses (::ffff:1.2.3.4) to their original
IPv4 form (1.2.3.4). The latter is needed on hosts that pre-date
IPV6_V6ONLY support (<a href="https://tools.ietf.org/html/rfc3493">RFC 3493</a>). 

 When IPv6 support is enabled via the <a href="postconf.5.html#inet_protocols">inet_protocols</a> parameter,
Postfix will do DNS type AAAA record lookups. 

 When both IPv4 and IPv6 support are enabled, the Postfix SMTP
client will choose the protocol as specified with the
<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> parameter. Postfix versions before 2.8
attempt to connect via IPv6 before attempting to use IPv4. 


Examples:


<pre>
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = all (DEFAULT)
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv6
<a href="postconf.5.html#inet_protocols">inet_protocols</a> = ipv4, ipv6
</pre>

</DD>

<DT><a name="info_log_address_format">info_log_address_format</a>
(default: external)</DT><DD>

 The email address form that will be used in non-debug logging
(info, warning, etc.). As of Postfix 3.5 when an address localpart
contains spaces or other special characters, the localpart will be
quoted, for example: 

<blockquote>
<pre>
 from=<"name with spaces"@example.com>
</pre>
</blockquote>

 Older Postfix versions would log the internal (unquoted) form: 

<blockquote>
<pre>
 from=<name with spaces@example.com>
</pre>
</blockquote>

 The external and internal forms are identical for the vast
majority of email addresses that contain no spaces or other special
characters in the localpart. 

 The logging in external form is consistent with the address
form that Postfix 3.2 and later prefer for most table lookups. This
is therefore the more useful form for non-debug logging. 

 Specify "<a href="postconf.5.html#info_log_address_format">info_log_address_format</a> = internal" for backwards
compatibility. 

 Postfix uses the unquoted form internally, because an attacker
can specify an email address in different forms by playing games
with quotes and backslashes. An attacker should not be able to use
such games to circumvent Postfix access policies. 

 This feature is available in Postfix 3.5 and later. 

</DD>

<DT><a name="initial_destination_concurrency">initial_destination_concurrency</a>
(default: 5)</DT><DD>


The initial per-destination concurrency level for parallel delivery
to the same destination.
With per-destination recipient limit > 1, a destination is a domain,
otherwise it is a recipient.


 Use <a href="postconf.5.html#transport_initial_destination_concurrency">transport_initial_destination_concurrency</a> to specify
a transport-specific override, where transport is the <a href="master.5.html">master.cf</a>
name of the message delivery transport (Postfix 2.5 and later). 


Warning: with concurrency of 1, one bad message can be enough to
block all mail to a site.


</DD>

<DT><a name="internal_mail_filter_classes">internal_mail_filter_classes</a>
(default: empty)</DT><DD>

 What categories of Postfix-generated mail are subject to
before-queue content inspection by <a href="postconf.5.html#non_smtpd_milters">non_smtpd_milters</a>, <a href="postconf.5.html#header_checks">header_checks</a>
and <a href="postconf.5.html#body_checks">body_checks</a>. Specify zero or more of the following, separated
by whitespace or comma. 

<dl>

<dt>bounce</dt> <dd> Inspect the content of delivery
status notifications. </dd>

<dt>notify</dt> <dd> Inspect the content of postmaster
notifications by the <a href="smtp.8.html">smtp(8)</a> and <a href="smtpd.8.html">smtpd(8)</a> processes. </dd>

</dl>

 NOTE: It's generally not safe to enable content inspection of
Postfix-generated email messages. The user is warned. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="invalid_hostname_reject_code">invalid_hostname_reject_code</a>
(default: 501)</DT><DD>


The numerical Postfix SMTP server response code when the client
HELO or EHLO command parameter is rejected by the <a href="postconf.5.html#reject_invalid_helo_hostname">reject_invalid_helo_hostname</a>
restriction.



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.


</DD>

<DT><a name="ipc_idle">ipc_idle</a>
(default: version dependent)</DT><DD>


The time after which a client closes an idle internal communication
channel. The purpose is to allow Postfix daemon processes to
terminate voluntarily after they become idle. This is used, for
example, by the Postfix address resolving and rewriting clients.


 With Postfix 2.4 the default value was reduced from 100s to 5s. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="ipc_timeout">ipc_timeout</a>
(default: 3600s)</DT><DD>


The time limit for sending or receiving information over an internal
communication channel. The purpose is to break out of deadlock
situations. If the time limit is exceeded the software aborts with a
fatal error.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="ipc_ttl">ipc_ttl</a>
(default: 1000s)</DT><DD>


The time after which a client closes an active internal communication
channel. The purpose is to allow Postfix daemon processes to
terminate voluntarily
after reaching their client limit. This is used, for example, by
the Postfix address resolving and rewriting clients.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="known_tcp_ports">known_tcp_ports</a>
(default: lmtp=24, smtp=25, smtps=submissions=465, submission=587)</DT><DD>

 Optional setting that avoids lookups in the services(5) database.
This feature was implemented to address inconsistencies in the name
of the port "465" service. The ABNF is:


<blockquote>

<a href="postconf.5.html#known_tcp_ports">known_tcp_ports</a> = empty | name-to-port *("," name-to-port) 
name-to-port = 1*(service-name "=') port-number

</blockquote>

 The comma is required. Whitespace is optional but it cannot appear
inside a service name or port number. 

 This feature is available in Postfix 3.6 and later. 

</DD>

<DT><a name="line_length_limit">line_length_limit</a>
(default: 2048)</DT><DD>

 Upon input, long lines are chopped up into pieces of at most
this length; upon delivery, long lines are reconstructed. 

</DD>

<DT><a name="lmdb_map_size">lmdb_map_size</a>
(default: 16777216)</DT><DD>


The initial OpenLDAP LMDB database size limit in bytes. Each time
a database becomes full, its size limit is doubled.



This feature is available in Postfix 2.11 and later.


</DD>

<DT><a name="lmtp_address_preference">lmtp_address_preference</a>
(default: ipv6)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="lmtp_address_verify_target">lmtp_address_verify_target</a>
(default: rcpt)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_address_verify_target">smtp_address_verify_target</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="lmtp_assume_final">lmtp_assume_final</a>
(default: no)</DT><DD>

 When a remote LMTP server announces no DSN support, assume that
the
server performs final delivery, and send "delivered" delivery status
notifications instead of "relayed". The default setting is backwards
compatible to avoid the infinitesimal possibility of breaking
existing LMTP-based content filters. 

</DD>

<DT><a name="lmtp_balance_inet_protocols">lmtp_balance_inet_protocols</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_balance_inet_protocols">smtp_balance_inet_protocols</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 3.3 and later. 

</DD>

<DT><a name="lmtp_bind_address">lmtp_bind_address</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_bind_address6">lmtp_bind_address6</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_bind_address_enforce">lmtp_bind_address_enforce</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_bind_address_enforce">smtp_bind_address_enforce</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 3.7 and later. 

</DD>

<DT><a name="lmtp_body_checks">lmtp_body_checks</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_body_checks">smtp_body_checks</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_cache_connection">lmtp_cache_connection</a>
(default: yes)</DT><DD>


Keep Postfix LMTP client connections open for up to $<a href="postconf.5.html#max_idle">max_idle</a>
seconds. When the LMTP client receives a request for the same
connection the connection is reused.


 This parameter is available in Postfix version 2.2 and earlier.
With Postfix version 2.3 and later, see <a href="postconf.5.html#lmtp_connection_cache_on_demand">lmtp_connection_cache_on_demand</a>,
<a href="postconf.5.html#lmtp_connection_cache_destinations">lmtp_connection_cache_destinations</a>, or <a href="postconf.5.html#lmtp_connection_reuse_time_limit">lmtp_connection_reuse_time_limit</a>.



The effectiveness of cached connections will be determined by the
number of remote LMTP servers in use, and the concurrency limit specified
for the Postfix LMTP client. Cached connections are closed under any of
the following conditions:


<ul>

<li> The Postfix LMTP client idle time limit is reached. This limit is
specified with the Postfix <a href="postconf.5.html#max_idle">max_idle</a> configuration parameter.

<li> A delivery request specifies a different destination than the
one currently cached.

<li> The per-process limit on the number of delivery requests is
reached. This limit is specified with the Postfix <a href="postconf.5.html#max_use">max_use</a>
configuration parameter.

<li> Upon the onset of another delivery request, the remote LMTP server
associated with the current session does not respond to the RSET
command.

</ul>


Most of these limitations have been with the Postfix
connection cache that is shared among multiple LMTP client
programs.


</DD>

<DT><a name="lmtp_cname_overrides_servername">lmtp_cname_overrides_servername</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_cname_overrides_servername">smtp_cname_overrides_servername</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_connect_timeout">lmtp_connect_timeout</a>
(default: 0s)</DT><DD>

 The Postfix LMTP client time limit for completing a TCP connection, or
zero (use the operating system built-in time limit). When no
connection can be made within the deadline, the LMTP client tries
the next address on the mail exchanger list. 

 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


Example:


<pre>
<a href="postconf.5.html#lmtp_connect_timeout">lmtp_connect_timeout</a> = 30s
</pre>

</DD>

<DT><a name="lmtp_connection_cache_destinations">lmtp_connection_cache_destinations</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_cache_destinations">smtp_connection_cache_destinations</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_connection_cache_on_demand">lmtp_connection_cache_on_demand</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_cache_on_demand">smtp_connection_cache_on_demand</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_connection_cache_time_limit">lmtp_connection_cache_time_limit</a>
(default: 2s)</DT><DD>

 The LMTP-specific version of the
<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a> configuration parameter.
See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_connection_reuse_count_limit">lmtp_connection_reuse_count_limit</a>
(default: 0)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_reuse_count_limit">smtp_connection_reuse_count_limit</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.11 and later. 

</DD>

<DT><a name="lmtp_connection_reuse_time_limit">lmtp_connection_reuse_time_limit</a>
(default: 300s)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_data_done_timeout">lmtp_data_done_timeout</a>
(default: 600s)</DT><DD>

 The Postfix LMTP client time limit for sending the LMTP ".",
and for receiving the remote LMTP server response. When no response
is received within the deadline, a warning is logged that the mail
may be delivered multiple times. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_data_init_timeout">lmtp_data_init_timeout</a>
(default: 120s)</DT><DD>


The Postfix LMTP client time limit for sending the LMTP DATA command,
and
for receiving the remote LMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_data_xfer_timeout">lmtp_data_xfer_timeout</a>
(default: 180s)</DT><DD>


The Postfix LMTP client time limit for sending the LMTP message
content.
When the connection stalls for more than $<a href="postconf.5.html#lmtp_data_xfer_timeout">lmtp_data_xfer_timeout</a>
the LMTP client terminates the transfer.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_defer_if_no_mx_address_found">lmtp_defer_if_no_mx_address_found</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_defer_if_no_mx_address_found">smtp_defer_if_no_mx_address_found</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_delivery_status_filter">lmtp_delivery_status_filter</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_delivery_status_filter">smtp_delivery_status_filter</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="lmtp_destination_concurrency_limit">lmtp_destination_concurrency_limit</a>
(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</DT><DD>

 The maximal number of parallel deliveries to the same destination
via the lmtp message delivery transport. This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the <a href="master.5.html">master.cf</a> file. 

</DD>

<DT><a name="lmtp_destination_recipient_limit">lmtp_destination_recipient_limit</a>
(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</DT><DD>

 The maximal number of recipients per message for the lmtp
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file. 

 Setting this parameter to a value of 1 changes the meaning of
<a href="postconf.5.html#lmtp_destination_concurrency_limit">lmtp_destination_concurrency_limit</a> from concurrency per domain into
concurrency per recipient. 

</DD>

<DT><a name="lmtp_discard_lhlo_keyword_address_maps">lmtp_discard_lhlo_keyword_address_maps</a>
(default: empty)</DT><DD>

 Lookup tables, indexed by the remote LMTP server address, with
case insensitive lists of LHLO keywords (pipelining, starttls,
auth, etc.) that the Postfix LMTP client will ignore in the LHLO
response
from a remote LMTP server. See <a href="postconf.5.html#lmtp_discard_lhlo_keywords">lmtp_discard_lhlo_keywords</a> for
details. The table is not indexed by hostname for consistency with
<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_discard_lhlo_keywords">lmtp_discard_lhlo_keywords</a>
(default: empty)</DT><DD>

 A case insensitive list of LHLO keywords (pipelining, starttls,
auth, etc.) that the Postfix LMTP client will ignore in the LHLO
response
from a remote LMTP server. 

 This feature is available in Postfix 2.3 and later. 

 Notes: 

<ul>

<li> Specify the silent-discard pseudo keyword to prevent
this action from being logged. 

<li> Use the <a href="postconf.5.html#lmtp_discard_lhlo_keyword_address_maps">lmtp_discard_lhlo_keyword_address_maps</a> feature to
discard LHLO keywords selectively. 

</ul>

</DD>

<DT><a name="lmtp_dns_reply_filter">lmtp_dns_reply_filter</a>
(default: empty)</DT><DD>

 Optional filter for Postfix LMTP client DNS lookup results.
See <a href="postconf.5.html#smtp_dns_reply_filter">smtp_dns_reply_filter</a> for details including an example. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="lmtp_dns_resolver_options">lmtp_dns_resolver_options</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_dns_resolver_options">smtp_dns_resolver_options</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="lmtp_dns_support_level">lmtp_dns_support_level</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.11 and later. 

</DD>

<DT><a name="lmtp_enforce_tls">lmtp_enforce_tls</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_enforce_tls">smtp_enforce_tls</a> configuration
parameter. See there for details. 

 This feature is deprecated as of Postfix 3.9. Specify
<a href="postconf.5.html#lmtp_tls_security_level">lmtp_tls_security_level</a> instead. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_fallback_relay">lmtp_fallback_relay</a>
(default: empty)</DT><DD>

 Optional list of relay hosts for LMTP destinations that can't be
found or that are unreachable. In <a href="postconf.5.html">main.cf</a> elements are separated by
whitespace or commas. 

 By default, mail is returned to the sender when a destination is not
found, and delivery is deferred when a destination is unreachable. 

 The fallback relays must be TCP destinations, specified without
a leading "inet:" prefix. Specify a host or host:port. Since MX
lookups do not apply with LMTP, there is no need to use the "[host]" or
"[host]:port" forms. If you specify multiple LMTP destinations, Postfix
will try them in the specified order. 


This feature is available in Postfix 3.1 and later.


</DD>

<DT><a name="lmtp_generic_maps">lmtp_generic_maps</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_generic_maps">smtp_generic_maps</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_header_checks">lmtp_header_checks</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_header_checks">smtp_header_checks</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_host_lookup">lmtp_host_lookup</a>
(default: dns)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_lhlo_name">lmtp_lhlo_name</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</DT><DD>


The hostname to send in the LMTP LHLO command.



The default value is the machine hostname. Specify a hostname or
[ip.add.re.ss] or [ip:v6:add:re::ss].



This information can be specified in the <a href="postconf.5.html">main.cf</a> file for all LMTP
clients, or it can be specified in the <a href="master.5.html">master.cf</a> file for a specific
client, for example:


<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
 mylmtp ... lmtp -o <a href="postconf.5.html#lmtp_lhlo_name">lmtp_lhlo_name</a>=foo.bar.com
</pre>
</blockquote>


This feature is available in Postfix 2.3 and later.


</DD>

<DT><a name="lmtp_lhlo_timeout">lmtp_lhlo_timeout</a>
(default: 300s)</DT><DD>

 The Postfix LMTP client time limit for sending the LHLO command,
and for receiving the initial remote LMTP server response. 

 Time units: s (seconds), m (minutes), h (hours), d (days), w
(weeks). The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_line_length_limit">lmtp_line_length_limit</a>
(default: 998)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_line_length_limit">smtp_line_length_limit</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_log_tls_feature_status">lmtp_log_tls_feature_status</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_log_tls_feature_status">smtp_log_tls_feature_status</a>
configuration parameter. See there for details. 

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="lmtp_mail_timeout">lmtp_mail_timeout</a>
(default: 300s)</DT><DD>


The Postfix LMTP client time limit for sending the MAIL FROM command,
and for receiving the remote LMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_mime_header_checks">lmtp_mime_header_checks</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_mime_header_checks">smtp_mime_header_checks</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_min_data_rate">lmtp_min_data_rate</a>
(default: 500)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_min_data_rate">smtp_min_data_rate</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 3.7 and later. 

</DD>

<DT><a name="lmtp_mx_address_limit">lmtp_mx_address_limit</a>
(default: 5)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_mx_address_limit">smtp_mx_address_limit</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_mx_session_limit">lmtp_mx_session_limit</a>
(default: 2)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_mx_session_limit">smtp_mx_session_limit</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_nested_header_checks">lmtp_nested_header_checks</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_nested_header_checks">smtp_nested_header_checks</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_per_record_deadline">lmtp_per_record_deadline</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_per_record_deadline">smtp_per_record_deadline</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.9 and later. 

</DD>

<DT><a name="lmtp_per_request_deadline">lmtp_per_request_deadline</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_per_request_deadline">smtp_per_request_deadline</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 3.7 and later. 

</DD>

<DT><a name="lmtp_pix_workaround_delay_time">lmtp_pix_workaround_delay_time</a>
(default: 10s)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_pix_workaround_maps">lmtp_pix_workaround_maps</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_maps">smtp_pix_workaround_maps</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.4 and later. 

</DD>

<DT><a name="lmtp_pix_workaround_threshold_time">lmtp_pix_workaround_threshold_time</a>
(default: 500s)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_pix_workarounds">lmtp_pix_workarounds</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the smtp_pix_workaround
configuration parameter. See there for details. 

 This feature is available in Postfix 2.4 and later. 

</DD>

<DT><a name="lmtp_quit_timeout">lmtp_quit_timeout</a>
(default: 300s)</DT><DD>


The Postfix LMTP client time limit for sending the QUIT command,
and for receiving the remote LMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_quote_rfc821_envelope">lmtp_quote_rfc821_envelope</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_randomize_addresses">lmtp_randomize_addresses</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_randomize_addresses">smtp_randomize_addresses</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_rcpt_timeout">lmtp_rcpt_timeout</a>
(default: 300s)</DT><DD>


The Postfix LMTP client time limit for sending the RCPT TO command,
and for receiving the remote LMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_reply_filter">lmtp_reply_filter</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.7 and later. 

</DD>

<DT><a name="lmtp_requiretls_policy">lmtp_requiretls_policy</a>
(default: opportunistic)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a>
configuration parameter. See there for details. 

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="lmtp_rset_timeout">lmtp_rset_timeout</a>
(default: 20s)</DT><DD>

 The Postfix LMTP client time limit for sending the RSET command,
and for receiving the remote LMTP server response. The LMTP client
sends RSET in
order to finish a recipient address probe, or to verify that a
cached connection is still alive. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="lmtp_sasl_auth_cache_name">lmtp_sasl_auth_cache_name</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_sasl_auth_cache_time">lmtp_sasl_auth_cache_time</a>
(default: 90d)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_sasl_auth_enable">lmtp_sasl_auth_enable</a>
(default: no)</DT><DD>


Enable SASL authentication in the Postfix LMTP client.


</DD>

<DT><a name="lmtp_sasl_auth_soft_bounce">lmtp_sasl_auth_soft_bounce</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_sasl_mechanism_filter">lmtp_sasl_mechanism_filter</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_sasl_password_maps">lmtp_sasl_password_maps</a>
(default: empty)</DT><DD>


Optional Postfix LMTP client lookup tables with one username:password entry
per host or domain. If a remote host or domain has no username:password
entry, then the Postfix LMTP client will not attempt to authenticate
to the remote host.


</DD>

<DT><a name="lmtp_sasl_password_result_delimiter">lmtp_sasl_password_result_delimiter</a>
(default: :)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_password_result_delimiter">smtp_sasl_password_result_delimiter</a>
configuration parameter. See there for details. 

</DD>

<DT><a name="lmtp_sasl_path">lmtp_sasl_path</a>
(default: empty)</DT><DD>

 Implementation-specific information that is passed through to
the SASL plug-in implementation that is selected with
<a href="postconf.5.html#lmtp_sasl_type">lmtp_sasl_type</a>. Typically this specifies the name of a
configuration file or rendezvous point. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_sasl_security_options">lmtp_sasl_security_options</a>
(default: noplaintext, noanonymous)</DT><DD>

 SASL security options; as of Postfix 2.3 the list of available
features depends on the SASL client implementation that is selected
with <a href="postconf.5.html#lmtp_sasl_type">lmtp_sasl_type</a>. 

 The following security features are defined for the cyrus
client SASL implementation: 

<dl>

<dt>noplaintext</dt>

<dd>Disallow authentication methods that use plaintext passwords. </dd>

<dt>noactive</dt>

<dd>Disallow authentication methods that are vulnerable to non-dictionary
active attacks. </dd>

<dt>nodictionary</dt>

<dd>Disallow authentication methods that are vulnerable to passive
dictionary attacks. </dd>

<dt>noanonymous</dt>

<dd>Disallow anonymous logins. </dd>

</dl>


Example:


<pre>
<a href="postconf.5.html#lmtp_sasl_security_options">lmtp_sasl_security_options</a> = noplaintext
</pre>

</DD>

<DT><a name="lmtp_sasl_tls_security_options">lmtp_sasl_tls_security_options</a>
(default: $<a href="postconf.5.html#lmtp_sasl_security_options">lmtp_sasl_security_options</a>)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_sasl_tls_verified_security_options">lmtp_sasl_tls_verified_security_options</a>
(default: $<a href="postconf.5.html#lmtp_sasl_tls_security_options">lmtp_sasl_tls_security_options</a>)</DT><DD>

 The LMTP-specific version of the
<a href="postconf.5.html#smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a> configuration parameter.
See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_sasl_type">lmtp_sasl_type</a>
(default: cyrus)</DT><DD>

 The SASL plug-in type that the Postfix LMTP client should use
for authentication. The available types are listed with the
"postconf -A" command. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_send_dummy_mail_auth">lmtp_send_dummy_mail_auth</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_send_dummy_mail_auth">smtp_send_dummy_mail_auth</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.9 and later. 

</DD>

<DT><a name="lmtp_send_xforward_command">lmtp_send_xforward_command</a>
(default: no)</DT><DD>


Send an XFORWARD command to the remote LMTP server when the LMTP LHLO
server response announces XFORWARD support. This allows an <a href="lmtp.8.html">lmtp(8)</a>
delivery agent, used for content filter message injection, to
forward the name, address, protocol and HELO name of the original
client to the content filter and downstream LMTP server.
Before you change the value to yes, it is best to make sure that
your content filter supports this command.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="lmtp_sender_dependent_authentication">lmtp_sender_dependent_authentication</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_sender_dependent_authentication">smtp_sender_dependent_authentication</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_skip_5xx_greeting">lmtp_skip_5xx_greeting</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_skip_quit_response">lmtp_skip_quit_response</a>
(default: no)</DT><DD>


Wait for the response to the LMTP QUIT command.


</DD>

<DT><a name="lmtp_starttls_timeout">lmtp_starttls_timeout</a>
(default: 300s)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_starttls_timeout">smtp_starttls_timeout</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tcp_port">lmtp_tcp_port</a>
(default: 24)</DT><DD>


The default TCP port that the Postfix LMTP client connects to.
Specify a symbolic name (see services(5)) or a numeric port.


</DD>

<DT><a name="lmtp_tls_CAfile">lmtp_tls_CAfile</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_CApath">lmtp_tls_CApath</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_block_early_mail_reply">lmtp_tls_block_early_mail_reply</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_block_early_mail_reply">smtp_tls_block_early_mail_reply</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.7 and later. 

</DD>

<DT><a name="lmtp_tls_cert_file">lmtp_tls_cert_file</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_chain_files">lmtp_tls_chain_files</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="lmtp_tls_ciphers">lmtp_tls_ciphers</a>
(default: medium)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_ciphers">smtp_tls_ciphers</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="lmtp_tls_connection_reuse">lmtp_tls_connection_reuse</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_connection_reuse">smtp_tls_connection_reuse</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="lmtp_tls_dcert_file">lmtp_tls_dcert_file</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_dkey_file">lmtp_tls_dkey_file</a>
(default: $<a href="postconf.5.html#lmtp_tls_dcert_file">lmtp_tls_dcert_file</a>)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_eccert_file">lmtp_tls_eccert_file</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.6 and later, when Postfix is
compiled and linked with OpenSSL 1.0.0 or later. 

</DD>

<DT><a name="lmtp_tls_eckey_file">lmtp_tls_eckey_file</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_eckey_file">smtp_tls_eckey_file</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.6 and later, when Postfix is
compiled and linked with OpenSSL 1.0.0 or later. 

</DD>

<DT><a name="lmtp_tls_enable_rpk">lmtp_tls_enable_rpk</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_enable_rpk">smtp_tls_enable_rpk</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 3.9 and later. 

</DD>

<DT><a name="lmtp_tls_enforce_peername">lmtp_tls_enforce_peername</a>
(default: yes)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_enforce_sts_mx_patterns">lmtp_tls_enforce_sts_mx_patterns</a>
(default: yes)</DT><DD>

 See <a href="postconf.5.html#smtp_tls_enforce_sts_mx_patterns">smtp_tls_enforce_sts_mx_patterns</a>. 

 This feature is available in Postfix ≥ 3.10.5. 

</DD>

<DT><a name="lmtp_tls_exclude_ciphers">lmtp_tls_exclude_ciphers</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_fingerprint_cert_match">lmtp_tls_fingerprint_cert_match</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_fingerprint_cert_match">smtp_tls_fingerprint_cert_match</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_tls_fingerprint_digest">lmtp_tls_fingerprint_digest</a>
(default: see "postconf -d" output)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_fingerprint_digest">smtp_tls_fingerprint_digest</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="lmtp_tls_force_insecure_host_tlsa_lookup">lmtp_tls_force_insecure_host_tlsa_lookup</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_force_insecure_host_tlsa_lookup">smtp_tls_force_insecure_host_tlsa_lookup</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.11 and later. 

</DD>

<DT><a name="lmtp_tls_key_file">lmtp_tls_key_file</a>
(default: $<a href="postconf.5.html#lmtp_tls_cert_file">lmtp_tls_cert_file</a>)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_loglevel">lmtp_tls_loglevel</a>
(default: 0)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_loglevel">smtp_tls_loglevel</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_mandatory_ciphers">lmtp_tls_mandatory_ciphers</a>
(default: medium)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_mandatory_exclude_ciphers">lmtp_tls_mandatory_exclude_ciphers</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_exclude_ciphers">smtp_tls_mandatory_exclude_ciphers</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_mandatory_protocols">lmtp_tls_mandatory_protocols</a>
(default: see 'postconf -d' output)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_mandatory_protocols">smtp_tls_mandatory_protocols</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_note_starttls_offer">lmtp_tls_note_starttls_offer</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_note_starttls_offer">smtp_tls_note_starttls_offer</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_per_site">lmtp_tls_per_site</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> configuration
parameter. See there for details. 

 This feature is deprecated as of Postfix 3.9. Specify
<a href="postconf.5.html#lmtp_tls_policy_maps">lmtp_tls_policy_maps</a> instead. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_policy_maps">lmtp_tls_policy_maps</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_protocols">lmtp_tls_protocols</a>
(default: see 'postconf -d' output)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_protocols">smtp_tls_protocols</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="lmtp_tls_scert_verifydepth">lmtp_tls_scert_verifydepth</a>
(default: 9)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_scert_verifydepth">smtp_tls_scert_verifydepth</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_secure_cert_match">lmtp_tls_secure_cert_match</a>
(default: nexthop)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_secure_cert_match">smtp_tls_secure_cert_match</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_security_level">lmtp_tls_security_level</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_servername">lmtp_tls_servername</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_servername">smtp_tls_servername</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="lmtp_tls_session_cache_database">lmtp_tls_session_cache_database</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_session_cache_database">smtp_tls_session_cache_database</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_session_cache_timeout">lmtp_tls_session_cache_timeout</a>
(default: 3600s)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_session_cache_timeout">smtp_tls_session_cache_timeout</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_trust_anchor_file">lmtp_tls_trust_anchor_file</a>
(default: empty)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_trust_anchor_file">smtp_tls_trust_anchor_file</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.11 and later. 

</DD>

<DT><a name="lmtp_tls_verify_cert_match">lmtp_tls_verify_cert_match</a>
(default: hostname)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_verify_cert_match">smtp_tls_verify_cert_match</a>
configuration parameter. See there for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_tls_wrappermode">lmtp_tls_wrappermode</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_tls_wrappermode">smtp_tls_wrappermode</a> configuration
parameter. See there for details. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="lmtp_use_tls">lmtp_use_tls</a>
(default: no)</DT><DD>

 The LMTP-specific version of the <a href="postconf.5.html#smtp_use_tls">smtp_use_tls</a> configuration
parameter. See there for details. 

 This feature is deprecated as of Postfix 3.9. Specify
<a href="postconf.5.html#lmtp_tls_security_level">lmtp_tls_security_level</a> instead. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="lmtp_xforward_timeout">lmtp_xforward_timeout</a>
(default: 300s)</DT><DD>


The Postfix LMTP client time limit for sending the XFORWARD command,
and for receiving the remote LMTP server response.



In case of problems the client does NOT try the next address on
the mail exchanger list.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="local_command_shell">local_command_shell</a>
(default: empty)</DT><DD>


Optional shell program for <a href="local.8.html">local(8)</a> delivery to non-Postfix commands.
By default, non-Postfix commands are executed directly; commands
are given to the default shell (typically, /bin/sh) only when they
contain shell meta characters or shell built-in commands.


 "sendmail's restricted shell" (smrsh) is what most people will
use in order to restrict what programs can be run from e.g. .forward
files (smrsh is part of the Sendmail distribution). 

 Note: when a shell program is specified, it is invoked even
when the command contains no shell built-in commands or meta
characters. 


Example:


<pre>
<a href="postconf.5.html#local_command_shell">local_command_shell</a> = /some/where/smrsh -c
<a href="postconf.5.html#local_command_shell">local_command_shell</a> = /bin/bash -c
</pre>

</DD>

<DT><a name="local_delivery_status_filter">local_delivery_status_filter</a>
(default: $<a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a>)</DT><DD>

 Optional filter for the <a href="local.8.html">local(8)</a> delivery agent to change the
status code or explanatory text of successful or unsuccessful
deliveries. See <a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a> for details. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="local_destination_concurrency_limit">local_destination_concurrency_limit</a>
(default: 2)</DT><DD>

 The maximal number of parallel deliveries via the local mail
delivery transport to the same recipient (when
"<a href="postconf.5.html#local_destination_recipient_limit">local_destination_recipient_limit</a> = 1") or the maximal number of
parallel deliveries to the same <a href="ADDRESS_CLASS_README.html#local_domain_class">local domain</a> (when
"<a href="postconf.5.html#local_destination_recipient_limit">local_destination_recipient_limit</a> > 1"). This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the <a href="master.5.html">master.cf</a> file. 

 A low limit of 2 is recommended, just in case someone has an
expensive shell command in a .forward file or in an alias (e.g.,
a mailing list manager). You don't want to run lots of those at
the same time. 

</DD>

<DT><a name="local_destination_recipient_limit">local_destination_recipient_limit</a>
(default: 1)</DT><DD>

 The maximal number of recipients per message delivery via the
local mail delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file. 

 Setting this parameter to a value > 1 changes the meaning of
<a href="postconf.5.html#local_destination_concurrency_limit">local_destination_concurrency_limit</a> from concurrency per recipient
into concurrency per domain. 

</DD>

<DT><a name="local_header_rewrite_clients">local_header_rewrite_clients</a>
(default: <a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a>)</DT><DD>

 Rewrite or add message headers in mail from these clients,
updating incomplete addresses with the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or
$<a href="postconf.5.html#mydomain">mydomain</a>, and adding missing headers. 

 See the <a href="postconf.5.html#append_at_myorigin">append_at_myorigin</a> and <a href="postconf.5.html#append_dot_mydomain">append_dot_mydomain</a> parameters
for details of how domain names are appended to incomplete addresses.


 See <a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> to optionally rewrite or add
message headers in mail from other clients. 

 Specify a list of zero or more of the following: 

<dl>

<dt><a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client IP address matches $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>. This is enabled by
default. </dd>

<dt><a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a></dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client IP address matches any network or network address listed in
$<a href="postconf.5.html#mynetworks">mynetworks</a>. This setting will not prevent remote mail header
address rewriting when mail from a remote client is forwarded by
a neighboring system. </dd>

<dt><a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a> </dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client is successfully authenticated via the <a href="https://tools.ietf.org/html/rfc4954">RFC 4954</a> (AUTH)
protocol. </dd>

<dt><a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a> </dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
remote SMTP client TLS certificate fingerprint or public key fingerprint
(Postfix 2.9 and later) is listed in $<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a>.
The fingerprint digest algorithm is configurable via the
<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
Postfix version 2.5). </dd>

<dd> The default algorithm is sha256 with Postfix ≥ 3.6
and the <a href="postconf.5.html#compatibility_level">compatibility_level</a> set to 3.6 or higher. With Postfix
≤ 3.5, the default algorithm is md5. The best-practice
algorithm is now sha256. Recent advances in hash function
cryptanalysis have led to md5 and sha1 being deprecated in favor of
sha256. However, as long as there are no known "second pre-image"
attacks against the older algorithms, their use in this context, though
not recommended, is still likely safe. </dd>

<dt><a href="postconf.5.html#permit_tls_all_clientcerts">permit_tls_all_clientcerts</a> </dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
remote SMTP client TLS certificate is successfully verified, regardless of
whether it is listed on the server, and regardless of the certifying
authority. </dd>

<dt><a name="check_address_map">check_address_map</a> <a href="DATABASE_README.html">type:table</a> </dt>

<dt><a href="DATABASE_README.html">type:table</a> </dt>

<dd> Append the domain name in $<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> when the
client IP address matches the specified lookup table.
The lookup result is ignored, and no subnet lookup is done. This
is suitable for, e.g., pop-before-smtp lookup tables. </dd>

</dl>

 Examples: 

 The Postfix < 2.2 backwards compatible setting: always rewrite
message headers, and always append my own domain to incomplete
header addresses. 

<blockquote>
<pre>
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all
</pre>
</blockquote>

 The purist (and default) setting: rewrite headers only in mail
from Postfix sendmail and in SMTP mail from this machine. 

<blockquote>
<pre>
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="postconf.5.html#permit_inet_interfaces">permit_inet_interfaces</a>
</pre>
</blockquote>

 The intermediate setting: rewrite header addresses and append
$<a href="postconf.5.html#myorigin">myorigin</a> or $<a href="postconf.5.html#mydomain">mydomain</a> information only with mail from Postfix
sendmail, from local clients, or from authorized SMTP clients. 

 Note: this setting will not prevent remote mail header address
rewriting when mail from a remote client is forwarded by a neighboring
system. 

<blockquote>
<pre>
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>,
 <a href="postconf.5.html#permit_sasl_authenticated">permit_sasl_authenticated</a> <a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a>
 <a href="postconf.5.html#check_address_map">check_address_map</a> <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/pop-before-smtp
</pre>
</blockquote>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

</DD>

<DT><a name="local_login_sender_maps">local_login_sender_maps</a>
(default: <a href="DATABASE_README.html#types">static</a>:*)</DT><DD>

 A list of lookup tables that are searched by the UNIX login name,
and that return a list of allowed envelope sender patterns separated
by space or comma. These sender patterns are enforced by the Postfix
<a href="postdrop.1.html">postdrop(1)</a> command. The default is backwards-compatible:
every user may specify any sender envelope address. 

 When no UNIX login name is available, the <a href="postdrop.1.html">postdrop(1)</a> command will
prepend "uid:" to the numerical UID and use that instead. 

 This feature ignores address extensions in the user-specified
envelope sender address. 

 Note: to enforce that the From: header address matches the envelope
sender (MAIL FROM) address, specify an external filter such as a Milter,
with the <a href="postconf.5.html#non_smtpd_milters">non_smtpd_milters</a> parameter. For example:
<a href="https://github.com/magcks/milterfrom">https://github.com/magcks/milterfrom</a>. 

 The following sender patterns are special; these cannot be used
as part of a longer pattern. 

<dl compact>

<dt> * <dd> This pattern allows any envelope sender address.
</dd>

<dt> <> </dt> <dd> This pattern allows the empty
envelope sender address. See the
<a href="postconf.5.html#empty_address_local_login_sender_maps_lookup_key">empty_address_local_login_sender_maps_lookup_key</a> configuration
parameter. </dd>

<dt> @domain </dt> <dd> This pattern allows an
envelope sender address when the '@' and domain part
match. </dd>

</dl>

 Examples: 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 # Allow root and postfix full control, anyone else can only
 # send mail as themselves. Use "uid:" followed by the numerical
 # UID when the UID has no entry in the UNIX password file.
 <a href="postconf.5.html#local_login_sender_maps">local_login_sender_maps</a> =
 <a href="DATABASE_README.html#types">inline</a>:{ { root = * }, { postfix = * } },
 <a href="pcre_table.5.html">pcre</a>:/etc/postfix/login_senders
</pre>

<pre>
/etc/postfix/login_senders:
 # Allow both the bare username and the user@domain forms.
 /(.+)/ $1 $1@example.com
</pre>

 This feature is available in Postfix 3.6 and later. 

</DD>

<DT><a name="local_recipient_maps">local_recipient_maps</a>
(default: <a href="proxymap.8.html">proxy</a>:unix:passwd.byname $<a href="postconf.5.html#alias_maps">alias_maps</a>)</DT><DD>

 Lookup tables with all names or addresses of valid local
recipients. A recipient address is local when its domain matches
$<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>. 

 If the <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> parameter value is non-empty (the
default), then the Postfix SMTP server queries <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a>
as specified in "<a href="LOCAL_RECIPIENT_README.html#format">Local
recipient table query format</a>", and rejects mail for unknown
local recipients. Other Postfix interfaces such as the Postfix
<a href="sendmail.1.html">sendmail(1)</a> command may still accept an "unknown" recipient. 

 The default <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> setting assumes that <a href="postconf.5.html#local_transport">local_transport</a>
specifies the UNIX-compatible <a href="local.8.html">local(8)</a> delivery agent which queries
the UNIX passwd database (typically, /etc.passwd) and the local
aliases database (typically, /etc/aliases). The <a href="proxymap.8.html">proxy</a>: agent allows
the Postfix SMTP server to access the UNIX passwd database from
outside a chroot jail. 

 For other local mail delivery configurations, see "<a href="LOCAL_RECIPIENT_README.html#change">When you need to
change the local_recipient_maps setting in main.cf</a>". 


Technically, tables listed with $<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> are used as
lists: The Postfix SMTP server needs to know only if a lookup string
is found or not, but it does not use the result from table lookup. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.



To turn off local recipient checking in the Postfix SMTP server,
specify "<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =" (i.e. empty).



Examples:


<pre>
<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =
</pre>

</DD>

<DT><a name="local_transport">local_transport</a>
(default: <a href="local.8.html">local</a>:$<a href="postconf.5.html#myhostname">myhostname</a>)</DT><DD>

 The default mail delivery transport and next-hop destination
for final delivery to domains listed with <a href="postconf.5.html#mydestination">mydestination</a>, and for
[ipaddress] destinations that match $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.
This information can be overruled with the <a href="transport.5.html">transport(5)</a> table. 


By default, local mail is delivered to the transport called "local",
which is just the name of a service that is defined the <a href="master.5.html">master.cf</a> file.



Specify a string of the form transport:nexthop, where transport
is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
The :nexthop destination is optional; its syntax is documented
in the manual page of the corresponding delivery agent.



Beware: if you override the default local delivery agent then you
need to review the <a href="LOCAL_RECIPIENT_README.html">LOCAL_RECIPIENT_README</a> document, otherwise the
SMTP server may reject mail for local recipients.


</DD>

<DT><a name="luser_relay">luser_relay</a>
(default: empty)</DT><DD>


Optional catch-all destination for unknown <a href="local.8.html">local(8)</a> recipients.
By default, mail for unknown recipients in domains that match
$<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> is returned
as undeliverable.



The <a href="postconf.5.html#luser_relay">luser_relay</a> value is not subject to Postfix configuration
parameter $name expansion. Instead, the following $name expansions
are done:


<dl>

<dt>$domain</dt>

<dd>The recipient domain. </dd>

<dt>$extension</dt>

<dd>The recipient address extension. </dd>

<dt>$home</dt>

<dd>The recipient's home directory. </dd>

<dt>$local</dt>

<dd>The entire recipient address localpart. </dd>

<dt>$recipient</dt>

<dd>The full recipient address. </dd>

<dt>$<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a></dt>

<dd>The address extension delimiter that was found in the recipient
address (Postfix 2.11 and later), or the system-wide recipient
address extension delimiter (Postfix 2.10 and earlier). </dd>

<dt>$shell</dt>

<dd>The recipient's login shell. </dd>

<dt>$user</dt>

<dd>The recipient username. </dd>

<dt>${name?value}</dt>

<dt>${name?{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is non-empty. </dd>

<dt>${name:value}</dt>

<dt>${name:{value}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value when $name is empty. </dd>

<dt>${name?{value1}:{value2}} (Postfix ≥ 3.0)</dt>

<dd>Expands to value1 when $name is non-empty,
value2 otherwise. </dd>

</dl>


Instead of $name you can also specify ${name} or $(name).



Note: <a href="postconf.5.html#luser_relay">luser_relay</a> works only for the Postfix <a href="local.8.html">local(8)</a> delivery agent.



Note: if you use this feature for accounts not in the UNIX password
file, then you must specify "<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> =" (i.e. empty)
in the <a href="postconf.5.html">main.cf</a> file, otherwise the Postfix SMTP server will reject mail
for non-UNIX accounts with "User unknown in local recipient table".



Examples:


<pre>
<a href="postconf.5.html#luser_relay">luser_relay</a> = $user@other.host
<a href="postconf.5.html#luser_relay">luser_relay</a> = $local@other.host
<a href="postconf.5.html#luser_relay">luser_relay</a> = admin+$local
</pre>

</DD>

<DT><a name="mail_name">mail_name</a>
(default: Postfix)</DT><DD>


The mail system name that is displayed in Received: headers, in
the SMTP greeting banner, and in bounced mail.


</DD>

<DT><a name="mail_owner">mail_owner</a>
(default: postfix)</DT><DD>


The UNIX system account that owns the Postfix queue and most Postfix
daemon processes. Specify the name of an unprivileged user account
that does not share a user or group ID with other accounts, and that
owns no other files
or processes on the system. In particular, don't specify nobody
or daemon. PLEASE USE A DEDICATED USER ID AND GROUP ID.



When this parameter value is changed you need to re-run "postfix
set-permissions" (with Postfix version 2.0 and earlier:
"/etc/postfix/post-install set-permissions".


</DD>

<DT><a name="mail_release_date">mail_release_date</a>
(default: see "postconf -d" output)</DT><DD>


The Postfix release date, in "YYYYMMDD" format.


</DD>

<DT><a name="mail_spool_directory">mail_spool_directory</a>
(default: see "postconf -d" output)</DT><DD>


The directory where <a href="local.8.html">local(8)</a> UNIX-style mailboxes are kept. The
default setting depends on the system type. Specify a name ending
in / for maildir-style delivery.



Note: maildir delivery is done with the privileges of the recipient.
If you use the <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> setting for maildir style
delivery, then you must create the top-level maildir directory in
advance. Postfix will not create it.



Examples:


<pre>
<a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> = /var/mail
<a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a> = /var/spool/mail
</pre>

</DD>

<DT><a name="mail_version">mail_version</a>
(default: see "postconf -d" output)</DT><DD>


The version of the mail system. Stable releases are named
major.minor.patchlevel. Experimental releases
also include the release date. The version string can be used in,
for example, the SMTP greeting banner.


</DD>

<DT><a name="mailbox_command">mailbox_command</a>
(default: empty)</DT><DD>


Optional external command that the <a href="local.8.html">local(8)</a> delivery agent should
use for mailbox delivery. The command is run with the user ID and
the primary group ID privileges of the recipient. Exception:
command delivery for root executes with $<a href="postconf.5.html#default_privs">default_privs</a> privileges.
This is not a problem, because 1) mail for root should always be
aliased to a real user and 2) don't log in as root, use "su" instead.



The following environment variables are exported to the command:


<dl>

<dt>CLIENT_ADDRESS</dt>

<dd>Remote client network address. Available in Postfix version 2.2 and
later. </dd>

<dt>CLIENT_HELO</dt>

<dd>Remote client EHLO command parameter. Available in Postfix version 2.2
and later.</dd>

<dt>CLIENT_HOSTNAME</dt>

<dd>Remote client hostname. Available in Postfix version 2.2 and later.
</dd>

<dt>CLIENT_PROTOCOL</dt>

<dd>Remote client protocol. Available in Postfix version 2.2 and later.
</dd>

<dt>DOMAIN</dt>

<dd>The domain part of the recipient address. </dd>

<dt>ENVID</dt>

<dd>The optional <a href="https://tools.ietf.org/html/rfc3461">RFC 3461</a> envelope ID. Available in Postfix version
3.9 and later</dd>

<dt>EXTENSION</dt>

<dd>The optional address extension. </dd>

<dt>HOME</dt>

<dd>The recipient home directory. </dd>

<dt>LOCAL</dt>

<dd>The recipient address localpart. </dd>

<dt>LOGNAME</dt>

<dd>The recipient's username. </dd>

<dt>ORIGINAL_RECIPIENT</dt>

<dd>The entire recipient address, before any address rewriting or
aliasing. </dd>

<dt>RECIPIENT</dt>

<dd>The full recipient address. </dd>

<dt>SASL_METHOD</dt>

<dd>SASL authentication method specified in the remote client AUTH
command. Available in Postfix version 2.2 and later. </dd>

<dt>SASL_SENDER</dt>

<dd>SASL sender address specified in the remote client MAIL FROM
command. Available in Postfix version 2.2 and later. </dd>

<dt>SASL_USER</dt>

<dd>SASL username specified in the remote client AUTH command.
Available in Postfix version 2.2 and later. </dd>

<dt>SENDER</dt>

<dd>The full sender address. </dd>

<dt>SHELL</dt>

<dd>The recipient's login shell. </dd>

<dt>USER</dt>

<dd>The recipient username. </dd>

</dl>


Unlike other Postfix configuration parameters, the <a href="postconf.5.html#mailbox_command">mailbox_command</a>
parameter is not subjected to $name substitutions. This is to make
it easier to specify shell syntax (see example below).



If you can, avoid shell meta characters because they will force
Postfix to run an expensive shell process. If you're delivering
via "procmail" then running a shell won't make a noticeable difference
in the total cost.



Note: if you use the <a href="postconf.5.html#mailbox_command">mailbox_command</a> feature to deliver mail
system-wide, you must set up an alias that forwards mail for root
to a real user.


 The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. 


Examples:


<pre>
<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/procmail
<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/procmail -a "$EXTENSION"
<a href="postconf.5.html#mailbox_command">mailbox_command</a> = /some/where/maildrop -d "$USER"
 -f "$SENDER" "$EXTENSION"
</pre>

</DD>

<DT><a name="mailbox_command_maps">mailbox_command_maps</a>
(default: empty)</DT><DD>


Optional lookup tables with per-recipient external commands to use
for <a href="local.8.html">local(8)</a> mailbox delivery. Behavior is as with <a href="postconf.5.html#mailbox_command">mailbox_command</a>.


 The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


</DD>

<DT><a name="mailbox_delivery_lock">mailbox_delivery_lock</a>
(default: see "postconf -d" output)</DT><DD>


How to lock a UNIX-style <a href="local.8.html">local(8)</a> mailbox before attempting delivery.
For a list of available file locking methods, use the "postconf
-l" command.



This setting is ignored with maildir style delivery,
because such deliveries are safe without explicit locks.



Note: The dotlock method requires that the recipient UID or
GID has write access to the parent directory of the mailbox file.



Note: the default setting of this parameter is system dependent.


</DD>

<DT><a name="mailbox_size_limit">mailbox_size_limit</a>
(default: 51200000)</DT><DD>

 The maximal size of any <a href="local.8.html">local(8)</a> individual mailbox or maildir
file, or zero (no limit). In fact, this limits the size of any
file that is written to upon local delivery, including files written
by external commands that are executed by the <a href="local.8.html">local(8)</a> delivery
agent. The value cannot exceed LONG_MAX (typically, a 32-bit or
64-bit signed integer).



This limit must not be smaller than the message size limit.


</DD>

<DT><a name="mailbox_transport">mailbox_transport</a>
(default: empty)</DT><DD>


Optional message delivery transport that the <a href="local.8.html">local(8)</a> delivery
agent should use for mailbox delivery to all local recipients,
whether or not they are found in the UNIX passwd database.


 The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. 

</DD>

<DT><a name="mailbox_transport_maps">mailbox_transport_maps</a>
(default: empty)</DT><DD>

 Optional lookup tables with per-recipient message delivery
transports to use for <a href="local.8.html">local(8)</a> mailbox delivery, whether or not the
recipients are found in the UNIX passwd database. 

 The precedence of <a href="local.8.html">local(8)</a> delivery features from high to low
is: aliases, .forward files, <a href="postconf.5.html#mailbox_transport_maps">mailbox_transport_maps</a>, <a href="postconf.5.html#mailbox_transport">mailbox_transport</a>,
<a href="postconf.5.html#mailbox_command_maps">mailbox_command_maps</a>, <a href="postconf.5.html#mailbox_command">mailbox_command</a>, <a href="postconf.5.html#home_mailbox">home_mailbox</a>, <a href="postconf.5.html#mail_spool_directory">mail_spool_directory</a>,
<a href="postconf.5.html#fallback_transport_maps">fallback_transport_maps</a>, <a href="postconf.5.html#fallback_transport">fallback_transport</a> and <a href="postconf.5.html#luser_relay">luser_relay</a>. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


 For safety reasons, this feature does not allow $number
substitutions in regular expression maps. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="maillog_file">maillog_file</a>
(default: empty)</DT><DD>

 The name of an optional logfile that is written by the Postfix
<a href="postlogd.8.html">postlogd(8)</a> service. An empty value selects logging to syslogd(8).
Specify "/dev/stdout" to select logging to standard output. Stdout
logging requires that Postfix is started with "postfix start-fg".


 Note 1: The <a href="postconf.5.html#maillog_file">maillog_file</a> parameter value must contain a prefix
that is specified with the <a href="postconf.5.html#maillog_file_prefixes">maillog_file_prefixes</a> parameter. 

 Note 2: Some Postfix non-daemon programs may still log information
to syslogd(8), before they have processed their configuration
parameters and command-line options. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="maillog_file_compressor">maillog_file_compressor</a>
(default: gzip)</DT><DD>

 The program to run after rotating $<a href="postconf.5.html#maillog_file">maillog_file</a> with "postfix
logrotate". The command is run with the rotated logfile name as its
first argument. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="maillog_file_permissions">maillog_file_permissions</a>
(default: 0600)</DT><DD>

 The file access permissions that will be set when the file
$<a href="postconf.5.html#maillog_file">maillog_file</a> is created for the first time, or when the file is
created after an existing file is rotated. Specify one of: 0600
(only super-user read/write access), 0640 (adds 'group' read
access), or 0644 (also adds 'other' read access). The leading
'0' is optional. 

 This feature is available in Postfix 3.9 and later. 

</DD>

<DT><a name="maillog_file_prefixes">maillog_file_prefixes</a>
(default: /var, /dev/stdout)</DT><DD>

 A list of allowed prefixes for a <a href="postconf.5.html#maillog_file">maillog_file</a> value. This is a
safety feature to contain the damage from a single configuration
mistake. Specify one or more prefix strings, separated by comma or
whitespace. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="maillog_file_rotate_suffix">maillog_file_rotate_suffix</a>
(default: %Y%m%d-%H%M%S)</DT><DD>

 The format of the suffix to append to $<a href="postconf.5.html#maillog_file">maillog_file</a> while rotating
the file with "postfix logrotate". See strftime(3) for syntax. The
default suffix, YYYYMMDD-HHMMSS, allows logs to be rotated frequently.


 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="mailq_path">mailq_path</a>
(default: see "postconf -d" output)</DT><DD>


Sendmail compatibility feature that specifies where the Postfix
<a href="mailq.1.html">mailq(1)</a> command is installed. This command can be used to
list the Postfix mail queue.


</DD>

<DT><a name="manpage_directory">manpage_directory</a>
(default: see "postconf -d" output)</DT><DD>


Where the Postfix manual pages are installed.


</DD>

<DT><a name="maps_rbl_domains">maps_rbl_domains</a>
(default: empty)</DT><DD>


Obsolete feature: use the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a> feature instead.


</DD>

<DT><a name="maps_rbl_reject_code">maps_rbl_reject_code</a>
(default: 554)</DT><DD>


The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a>, <a href="postconf.5.html#reject_rhsbl_client">reject_rhsbl_client</a>,
<a href="postconf.5.html#reject_rhsbl_reverse_client">reject_rhsbl_reverse_client</a>, <a href="postconf.5.html#reject_rhsbl_sender">reject_rhsbl_sender</a> or
<a href="postconf.5.html#reject_rhsbl_recipient">reject_rhsbl_recipient</a> restriction.



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.


</DD>

<DT><a name="masquerade_classes">masquerade_classes</a>
(default: envelope_sender, header_sender, header_recipient)</DT><DD>


What addresses are subject to address masquerading.



By default, address masquerading is limited to envelope sender
addresses, and to header sender and header recipient addresses.
This allows you to use address masquerading on a mail gateway while
still being able to forward mail to users on individual machines.



Specify zero or more of: envelope_sender, envelope_recipient,
header_sender, header_recipient


</DD>

<DT><a name="masquerade_domains">masquerade_domains</a>
(default: empty)</DT><DD>


Optional list of domains whose subdomain structure will be stripped
off in email addresses.



The list is processed left to right, and processing stops at the
first match. Thus,


<blockquote>
<pre>
<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = foo.example.com example.com
</pre>
</blockquote>


strips "user@any.thing.foo.example.com" to "user@foo.example.com",
but strips "user@any.thing.else.example.com" to "user@example.com".



A domain name prefixed with ! means do not masquerade this domain
or its subdomains. Thus,


<blockquote>
<pre>
<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = !foo.example.com example.com
</pre>
</blockquote>


does not change "user@any.thing.foo.example.com" or "user@foo.example.com",
but strips "user@any.thing.else.example.com" to "user@example.com".


 Note: with Postfix version 2.2, message header address masquerading
happens only when message header address rewriting is enabled: 

<ul>

<li> The message is received with the Postfix <a href="sendmail.1.html">sendmail(1)</a> command,

<li> The message is received from a network client that matches
$<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a>,

<li> The message is received from the network, and the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter specifies a non-empty value.

</ul>

 To get the behavior before Postfix version 2.2, specify
"<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> = <a href="DATABASE_README.html#types">static</a>:all". 


Example:


<pre>
<a href="postconf.5.html#masquerade_domains">masquerade_domains</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
</pre>

</DD>

<DT><a name="masquerade_exceptions">masquerade_exceptions</a>
(default: empty)</DT><DD>


Optional list of user names that are not subjected to address
masquerading, even when their addresses match $<a href="postconf.5.html#masquerade_domains">masquerade_domains</a>.



By default, address masquerading makes no exceptions.



Specify a list of user names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. A "/file/name"
pattern is replaced
by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a name
matches a lookup key (the lookup result is ignored). Continue long
lines by starting the next line with whitespace. Specify "!pattern"
to exclude a name from the list. The form "!/file/name" is supported
only in Postfix version 2.4 and later. 


Examples:


<pre>
<a href="postconf.5.html#masquerade_exceptions">masquerade_exceptions</a> = root, mailer-daemon
<a href="postconf.5.html#masquerade_exceptions">masquerade_exceptions</a> = root
</pre>

</DD>

<DT><a name="master_service_disable">master_service_disable</a>
(default: empty)</DT><DD>

 Selectively disable <a href="master.8.html">master(8)</a> listener ports by service type
or by service name and type. Specify a list of service types
("inet", "unix", "fifo", or "pass") or "name/type" tuples, where
"name" is the first field of a <a href="master.5.html">master.cf</a> entry and "type" is a
service type. As with other Postfix matchlists, a search stops at
the first match. Specify "!pattern" to exclude a service from the
list. By default, all <a href="master.8.html">master(8)</a> listener ports are enabled. 

 Note: this feature does not support "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
patterns, nor does it support wildcards such as "*" or "all". This
is intentional. 

 Examples: 

<pre>
# With Postfix 2.6..2.10 use '.' instead of '/'.
# Turn on all <a href="master.8.html">master(8)</a> listener ports (the default).
<a href="postconf.5.html#master_service_disable">master_service_disable</a> =
# Turn off only the main SMTP listener port.
<a href="postconf.5.html#master_service_disable">master_service_disable</a> = smtp/inet
# Turn off all TCP/IP listener ports.
<a href="postconf.5.html#master_service_disable">master_service_disable</a> = inet
# Turn off all TCP/IP listener ports except "foo".
<a href="postconf.5.html#master_service_disable">master_service_disable</a> = !foo/inet, inet
</pre>

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="max_idle">max_idle</a>
(default: 100s)</DT><DD>


The maximum amount of time that an idle Postfix daemon process waits
for an incoming connection before terminating voluntarily. This
parameter
is ignored by the Postfix queue manager and by other long-lived
Postfix daemon processes.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="max_use">max_use</a>
(default: 100)</DT><DD>


The maximal number of incoming connections that a Postfix daemon
process will service before terminating voluntarily. This parameter
is ignored by the Postfix queue
manager and by other long-lived Postfix daemon processes.


</DD>

<DT><a name="maximal_backoff_time">maximal_backoff_time</a>
(default: 4000s)</DT><DD>


The maximal time between attempts to deliver a deferred message.


 This parameter should be set to a value greater than or equal
to $<a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a>. See also $<a href="postconf.5.html#queue_run_delay">queue_run_delay</a>. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="maximal_queue_lifetime">maximal_queue_lifetime</a>
(default: 5d)</DT><DD>


Consider a message as undeliverable, when delivery fails with a
temporary error, and the time in the queue has reached the
<a href="postconf.5.html#maximal_queue_lifetime">maximal_queue_lifetime</a> limit.


 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 


Specify 0 when mail delivery should be tried only once.


</DD>

<DT><a name="message_drop_headers">message_drop_headers</a>
(default: bcc, content-length, resent-bcc, return-path)</DT><DD>

 Names of message headers that the <a href="cleanup.8.html">cleanup(8)</a> daemon will remove
after applying <a href="header_checks.5.html">header_checks(5)</a> and before invoking Milter applications.
The default setting is compatible with Postfix < 3.0. 

 Specify a list of header names, separated by comma or space.
Names are matched in a case-insensitive manner. The list of supported
header names is limited only by available memory. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="message_reject_characters">message_reject_characters</a>
(default: empty)</DT><DD>

 The set of characters that Postfix will reject in message
content. The usual C-like escape sequences are recognized: <tt>\a
\b \f \n \r \t \v \ddd</tt> (up to three octal digits) and
<tt>\\</tt>. 

 Note 1: this feature does not recognize text that requires MIME
decoding. It inspects raw message content, just like <a href="postconf.5.html#header_checks">header_checks</a>
and <a href="postconf.5.html#body_checks">body_checks</a>. 

 Note 2: this feature is disabled with "<a href="postconf.5.html#receive_override_options">receive_override_options</a>
= <a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>". 

 Example: 

<pre>
<a href="postconf.5.html#message_reject_characters">message_reject_characters</a> = \0
</pre>

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="message_size_limit">message_size_limit</a>
(default: 10240000)</DT><DD>


The maximal size in bytes of a message, including envelope information.
The value cannot exceed LONG_MAX (typically, a 32-bit or 64-bit
signed integer).


 Note: be careful when making changes. Excessively small values
will result in the loss of non-delivery notifications, when a bounce
message size exceeds the local or remote MTA's message size limit.


</DD>

<DT><a name="message_strip_characters">message_strip_characters</a>
(default: empty)</DT><DD>

 The set of characters that Postfix will remove from message
content. The usual C-like escape sequences are recognized: <tt>\a
\b \f \n \r \t \v \ddd</tt> (up to three octal digits) and
<tt>\\</tt>. 

 Note 1: this feature does not recognize text that requires MIME
decoding. It inspects raw message content, just like <a href="postconf.5.html#header_checks">header_checks</a>
and <a href="postconf.5.html#body_checks">body_checks</a>. 

 Note 2: this feature is disabled with "<a href="postconf.5.html#receive_override_options">receive_override_options</a>
= <a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>". 

 Example: 

<pre>
<a href="postconf.5.html#message_strip_characters">message_strip_characters</a> = \0
</pre>

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="meta_directory">meta_directory</a>
(default: see 'postconf -d' output)</DT><DD>

 The location of non-executable files that are shared among
multiple Postfix instances, such as postfix-files, dynamicmaps.cf,
and the multi-instance template files <a href="postconf.5.html">main.cf</a>.proto and <a href="master.5.html">master.cf</a>.proto.
This directory should contain only Postfix-related files. Typically,
the <a href="postconf.5.html#meta_directory">meta_directory</a> parameter has the same default as the <a href="postconf.5.html#config_directory">config_directory</a>
parameter (/etc/postfix or /usr/local/etc/postfix). 

 For backwards compatibility with Postfix versions 2.6..2.11,
specify "<a href="postconf.5.html#meta_directory">meta_directory</a> = $<a href="postconf.5.html#daemon_directory">daemon_directory</a>" in <a href="postconf.5.html">main.cf</a> before
installing or upgrading Postfix, or specify "<a href="postconf.5.html#meta_directory">meta_directory</a> =
/path/name" on the "make makefiles", "make install" or "make upgrade"
command line. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="milter_command_timeout">milter_command_timeout</a>
(default: 30s)</DT><DD>

 The time limit for sending an SMTP command to a Milter (mail
filter) application, and for receiving the response. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_connect_macros">milter_connect_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to Milter (mail filter) applications
after completion of an SMTP connection. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_connect_timeout">milter_connect_timeout</a>
(default: 30s)</DT><DD>

 The time limit for connecting to a Milter (mail filter)
application, and for negotiating protocol options. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_content_timeout">milter_content_timeout</a>
(default: 300s)</DT><DD>

 The time limit for sending message content to a Milter (mail
filter) application, and for receiving the response. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_data_macros">milter_data_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to version 4 or higher Milter (mail
filter) applications after the SMTP DATA command. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_default_action">milter_default_action</a>
(default: Postfix ≥ 3.11: shutdown; Postfix < 3.11: tempfail)</DT><DD>

 The default action when a Milter (mail filter) response is
unavailable (for example, bad Postfix configuration or Milter
failure). Specify one of the following: 

<dl compact>

<dt>accept</dt> <dd>Proceed as if the mail filter was not present.
</dd>

<dt>reject</dt> <dd>Reject all further commands in this session
with a permanent status code.</dd>

<dt>tempfail</dt> <dd>Reject all further commands in this session
with a temporary status code. </dd>

<dt>shutdown</dt> <dd>With <a href="postconf.5.html#smtpd_milters">smtpd_milters</a>, close the SMTP connection
after sending a 421 SMTP reply; with <a href="postconf.5.html#non_smtpd_milters">non_smtpd_milters</a>, report a
queue file write error. Available in Postfix 3.11 and later. </dd>

<dt>quarantine</dt> <dd>Like "accept", but freeze the message in
the "<a href="QSHAPE_README.html#hold_queue">hold" queue</a>. Available with Postfix 2.6 and later. </dd>

</dl>

 The default action was "tempfail" with Postfix 3.10 and earlier.


 The default action is "shutdown" with Postfix 3.11 and later,
i.e. disconnect the SMTP client. With the old default, Postfix could
tempfail all messages that the client sends over a long-lived
connection, even if a Milter failure is only temporary. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_end_of_data_macros">milter_end_of_data_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to Milter (mail filter) applications
after the message end-of-data. See <a href="MILTER_README.html">MILTER_README</a> for a list of
available macro names and their meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_end_of_header_macros">milter_end_of_header_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to Milter (mail filter) applications
after the end of the message header. See <a href="MILTER_README.html">MILTER_README</a> for a list
of available macro names and their meanings. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="milter_header_checks">milter_header_checks</a>
(default: empty)</DT><DD>

 Optional lookup tables for content inspection of message headers
that are produced by Milter applications. See the <a href="header_checks.5.html">header_checks(5)</a>
manual page available actions. Currently, PREPEND is not implemented.


 The following example sends all mail that is marked as SPAM to
a spam handling machine. Note that matches are case-insensitive
by default. 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#milter_header_checks">milter_header_checks</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/<a href="postconf.5.html#milter_header_checks">milter_header_checks</a>
</pre>

<pre>
/etc/postfix/<a href="postconf.5.html#milter_header_checks">milter_header_checks</a>:
 /^X-SPAM-FLAG:\s+YES/ FILTER mysmtp:sanitizer.example.com:25
</pre>

 The <a href="postconf.5.html#milter_header_checks">milter_header_checks</a> mechanism could also be used for
allowlisting. For example it could be used to skip heavy content
inspection for DKIM-signed mail from known friendly domains. 

 This feature is available in Postfix 2.7, and as an optional
patch for Postfix 2.6. 

</DD>

<DT><a name="milter_helo_macros">milter_helo_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to Milter (mail filter) applications
after the SMTP HELO or EHLO command. See
<a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their meanings.


 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_macro_daemon_name">milter_macro_daemon_name</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</DT><DD>

 The {daemon_name} macro value for Milter (mail filter) applications.
See <a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their
meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_macro_defaults">milter_macro_defaults</a>
(default: empty)</DT><DD>

 Optional list of name=value pairs that specify default
values for arbitrary macros that Postfix may send to Milter
applications. These defaults are used when there is no corresponding
information from the message delivery context. 

 Specify name=value or {name=value} pairs separated
by comma or whitespace. Enclose a pair in "{}" when a value contains
comma or whitespace (this form ignores whitespace after the enclosing
"{", around the "=", and before the enclosing "}"). 

 This feature is available in Postfix 3.1 and later. 

</DD>

<DT><a name="milter_macro_v">milter_macro_v</a>
(default: $<a href="postconf.5.html#mail_name">mail_name</a> $<a href="postconf.5.html#mail_version">mail_version</a>)</DT><DD>

 The {v} macro value for Milter (mail filter) applications.
See <a href="MILTER_README.html">MILTER_README</a> for a list of available macro names and their
meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_mail_macros">milter_mail_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to Milter (mail filter) applications
after the SMTP MAIL FROM command. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_protocol">milter_protocol</a>
(default: 6)</DT><DD>

 The mail filter protocol version and optional protocol extensions
for communication with a Milter application; prior to Postfix 2.6
the default protocol is 2. Postfix
sends this version number during the initial protocol handshake.
It should match the version number that is expected by the mail
filter application (or by its Milter library). 

Protocol versions: 

<dl compact>

<dt>2</dt> <dd>Use Sendmail 8 mail filter protocol version 2 (default
with Sendmail version 8.11 .. 8.13 and Postfix version 2.3 ..
2.5).</dd>

<dt>3</dt> <dd>Use Sendmail 8 mail filter protocol version 3.</dd>

<dt>4</dt> <dd>Use Sendmail 8 mail filter protocol version 4.</dd>

<dt>6</dt> <dd>Use Sendmail 8 mail filter protocol version 6 (default
with Sendmail version 8.14 and Postfix version 2.6).</dd>

</dl>

Protocol extensions: 

<dl compact>

<dt>no_header_reply</dt> <dd> Specify this when the Milter application
will not reply for each individual message header.</dd>

</dl>

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_rcpt_macros">milter_rcpt_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to Milter (mail filter) applications
after the SMTP RCPT TO command. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="milter_unknown_command_macros">milter_unknown_command_macros</a>
(default: see "postconf -d" output)</DT><DD>

 The macros that are sent to version 3 or higher Milter (mail
filter) applications after an unknown SMTP command. See <a href="MILTER_README.html">MILTER_README</a>
for a list of available macro names and their meanings. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="mime_boundary_length_limit">mime_boundary_length_limit</a>
(default: 2048)</DT><DD>


The maximal length of MIME multipart boundary strings. The MIME
processor is unable to distinguish between boundary strings that
do not differ in the first $<a href="postconf.5.html#mime_boundary_length_limit">mime_boundary_length_limit</a> characters.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="mime_header_checks">mime_header_checks</a>
(default: $<a href="postconf.5.html#header_checks">header_checks</a>)</DT><DD>


Optional lookup tables for content inspection of MIME related
message headers, as described in the <a href="header_checks.5.html">header_checks(5)</a> manual page.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="mime_nesting_limit">mime_nesting_limit</a>
(default: 100)</DT><DD>


The maximal recursion level that the MIME processor will handle.
Postfix refuses mail that is nested deeper than the specified limit.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="minimal_backoff_time">minimal_backoff_time</a>
(default: 300s)</DT><DD>


The minimal time between attempts to deliver a deferred message;
prior to Postfix 2.4 the default value was 1000s.



This parameter also limits the time an unreachable destination is
kept in the short-term, in-memory, destination status cache.


 This parameter should be set greater than or equal to
$<a href="postconf.5.html#queue_run_delay">queue_run_delay</a>. See also $<a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a>. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="multi_instance_directories">multi_instance_directories</a>
(default: empty)</DT><DD>

 An optional list of non-default Postfix configuration directories;
these directories belong to additional Postfix instances that share
the Postfix executable files and documentation with the default
Postfix instance, and that are started, stopped, etc., together
with the default Postfix instance. Specify a list of pathnames
separated by comma or whitespace. 

 When $<a href="postconf.5.html#multi_instance_directories">multi_instance_directories</a> is empty, the <a href="postfix.1.html">postfix(1)</a> command
runs in single-instance mode and operates on a single Postfix
instance only. Otherwise, the <a href="postfix.1.html">postfix(1)</a> command runs in multi-instance
mode and invokes the multi-instance manager specified with the
<a href="postconf.5.html#multi_instance_wrapper">multi_instance_wrapper</a> parameter. The multi-instance manager in
turn executes <a href="postfix.1.html">postfix(1)</a> commands for the default instance and for
all Postfix instances in $<a href="postconf.5.html#multi_instance_directories">multi_instance_directories</a>. 

 Currently, this parameter setting is ignored except for the
default <a href="postconf.5.html">main.cf</a> file. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="multi_instance_enable">multi_instance_enable</a>
(default: no)</DT><DD>

 Allow this Postfix instance to be started, stopped, etc., by a
multi-instance manager. By default, new instances are created in
a safe state that prevents them from being started inadvertently.
This parameter is reserved for the multi-instance manager. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="multi_instance_group">multi_instance_group</a>
(default: empty)</DT><DD>

 The optional instance group name of this Postfix instance. A
group identifies closely-related Postfix instances that the
multi-instance manager can start, stop, etc., as a unit. This
parameter is reserved for the multi-instance manager. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="multi_instance_name">multi_instance_name</a>
(default: empty)</DT><DD>

 The optional instance name of this Postfix instance. This name
becomes also the default value for the <a href="postconf.5.html#syslog_name">syslog_name</a> parameter. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="multi_instance_wrapper">multi_instance_wrapper</a>
(default: empty)</DT><DD>

 The pathname of a multi-instance manager command that the
<a href="postfix.1.html">postfix(1)</a> command invokes when the <a href="postconf.5.html#multi_instance_directories">multi_instance_directories</a>
parameter value is non-empty. The pathname may be followed by
initial command arguments separated by whitespace; shell
metacharacters such as quotes are not supported in this context.


 The <a href="postfix.1.html">postfix(1)</a> command invokes the manager command with the
<a href="postfix.1.html">postfix(1)</a> non-option command arguments on the manager command line,
and with all installation configuration parameters exported into
the manager command process environment. The manager command in
turn invokes the <a href="postfix.1.html">postfix(1)</a> command for individual Postfix instances
as "postfix -c <a href="postconf.5.html#config_directory">config_directory</a> command". 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="multi_recipient_bounce_reject_code">multi_recipient_bounce_reject_code</a>
(default: 550)</DT><DD>


The numerical Postfix SMTP server response code when a remote SMTP
client request is blocked by the <a href="postconf.5.html#reject_multi_recipient_bounce">reject_multi_recipient_bounce</a>
restriction.



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="mydestination">mydestination</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a>, localhost)</DT><DD>

 The list of domains that are delivered via the $<a href="postconf.5.html#local_transport">local_transport</a>
mail delivery transport. By default this is the Postfix <a href="local.8.html">local(8)</a>
delivery agent which looks up all recipients in /etc/passwd and
/etc/aliases. The SMTP server validates recipient addresses with
$<a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> and rejects non-existent recipients. See also
the <a href="ADDRESS_CLASS_README.html#local_domain_class">local domain</a> class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file.



The default <a href="postconf.5.html#mydestination">mydestination</a> value specifies names for the local
machine only. On a mail domain gateway, you should also include
$<a href="postconf.5.html#mydomain">mydomain</a>.



The $<a href="postconf.5.html#local_transport">local_transport</a> delivery method is also selected for mail
addressed to user@[the.net.work.address] of the mail system (the
IP addresses specified with the <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> and <a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>
parameters).



Warnings:


<ul>

<li>Do not specify the names of virtual domains - those domains
are specified elsewhere. See <a href="VIRTUAL_README.html">VIRTUAL_README</a> for more information. 

<li>Do not specify the names of domains that this machine is
backup MX host for. See <a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> for how to
set up backup MX hosts. 

<li>By default, the Postfix SMTP server rejects mail for recipients
not listed with the <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a> parameter. See the
<a href="postconf.5.html">postconf(5)</a> manual for a description of the <a href="postconf.5.html#local_recipient_maps">local_recipient_maps</a>
and <a href="postconf.5.html#unknown_local_recipient_reject_code">unknown_local_recipient_reject_code</a> parameters. 

</ul>


Specify a list of host or domain names, "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
patterns, separated by commas and/or whitespace. A "/file/name"
pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>" lookup table
is matched when a name matches a lookup key (the lookup result is
ignored). Continue long lines by starting the next line with
whitespace. 


Examples:


<pre>
<a href="postconf.5.html#mydestination">mydestination</a> = $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a> $<a href="postconf.5.html#mydomain">mydomain</a>
<a href="postconf.5.html#mydestination">mydestination</a> = $<a href="postconf.5.html#myhostname">myhostname</a>, localhost.$<a href="postconf.5.html#mydomain">mydomain</a> www.$<a href="postconf.5.html#mydomain">mydomain</a>, ftp.$<a href="postconf.5.html#mydomain">mydomain</a>
</pre>

</DD>

<DT><a name="mydomain">mydomain</a>
(default: see "postconf -d" output)</DT><DD>


The internet domain name of this mail system. The default is to
use $<a href="postconf.5.html#myhostname">myhostname</a> minus the first component, or "localdomain" (Postfix
2.3 and later). $<a href="postconf.5.html#mydomain">mydomain</a> is used as
a default value for many other configuration parameters.



Example:


<pre>
<a href="postconf.5.html#mydomain">mydomain</a> = domain.tld
</pre>

</DD>

<DT><a name="myhostname">myhostname</a>
(default: see "postconf -d" output)</DT><DD>


The internet hostname of this mail system. The default is to use
the fully-qualified domain name (FQDN) from gethostname(), or to
use the non-FQDN result from gethostname() and append ".$<a href="postconf.5.html#mydomain">mydomain</a>".
$<a href="postconf.5.html#myhostname">myhostname</a> is used as a default value for many other configuration
parameters. 


Example:


<pre>
<a href="postconf.5.html#myhostname">myhostname</a> = host.example.com
</pre>

</DD>

<DT><a name="mynetworks">mynetworks</a>
(default: see "postconf -d" output)</DT><DD>


The list of "trusted" remote SMTP clients that have more privileges than
"strangers".



In particular, "trusted" SMTP clients are allowed to relay mail
through Postfix. See the <a href="postconf.5.html#smtpd_relay_restrictions">smtpd_relay_restrictions</a> parameter
description in the <a href="postconf.5.html">postconf(5)</a> manual.



You can specify the list of "trusted" network addresses by hand
or you can let Postfix do it for you (which is the default).
See the description of the <a href="postconf.5.html#mynetworks_style">mynetworks_style</a> parameter for more
information.



If you specify the <a href="postconf.5.html#mynetworks">mynetworks</a> list by hand,
Postfix ignores the <a href="postconf.5.html#mynetworks_style">mynetworks_style</a> setting.


 Specify a list of network addresses or network/netmask patterns,
separated by commas and/or whitespace. Continue long lines by
starting the next line with whitespace. 

 The netmask specifies the number of bits in the network part
of a host address. You can also specify "/file/name" or "<a href="DATABASE_README.html">type:table</a>"
patterns. A "/file/name" pattern is replaced by its contents; a
"<a href="DATABASE_README.html">type:table</a>" lookup table is matched when a table entry matches a
lookup string (the lookup result is ignored). 

 The list is matched left to right, and the search stops on the
first match. Specify "!pattern" to exclude an address or network
block from the list. The form "!/file/name" is supported only
in Postfix version 2.4 and later. 

 Note 1: Pattern matching of domain names is controlled by the
presence or absence of "<a href="postconf.5.html#mynetworks">mynetworks</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
parameter value. 

 Note 2: IP version 6 address information must be specified inside
<tt>[]</tt> in the <a href="postconf.5.html#mynetworks">mynetworks</a> value, and in files specified with
"/file/name". IP version 6 addresses contain the ":" character,
and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>" pattern. 

 Note 3: CIDR ranges cannot be specified in hash tables. Use cidr
tables if CIDR ranges are used. 

 Examples: 

<pre>
<a href="postconf.5.html#mynetworks">mynetworks</a> = 127.0.0.0/8 168.100.189.0/28
<a href="postconf.5.html#mynetworks">mynetworks</a> = !192.168.0.1, 192.168.0.0/28
<a href="postconf.5.html#mynetworks">mynetworks</a> = 127.0.0.0/8 168.100.189.0/28 [::1]/128 [2001:240:587::]/64
<a href="postconf.5.html#mynetworks">mynetworks</a> = $<a href="postconf.5.html#config_directory">config_directory</a>/mynetworks
<a href="postconf.5.html#mynetworks">mynetworks</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/network_table
<a href="postconf.5.html#mynetworks">mynetworks</a> = <a href="cidr_table.5.html">cidr</a>:/etc/postfix/network_table.cidr
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

</DD>

<DT><a name="mynetworks_style">mynetworks_style</a>
(default: Postfix ≥ 3.0: host, Postfix < 3.0: subnet)</DT><DD>


The method to generate the default value for the <a href="postconf.5.html#mynetworks">mynetworks</a> parameter.
This is the list of trusted networks for relay access control etc.


<ul>

<li>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = host" when Postfix should
"trust" only the local machine. 

<li>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = subnet" when Postfix
should "trust" remote SMTP clients in the same IP subnetworks as the local
machine. On Linux, this works correctly only with interfaces
specified with the "ifconfig" or "ip" command. 

<li>Specify "<a href="postconf.5.html#mynetworks_style">mynetworks_style</a> = class" when Postfix should
"trust" remote SMTP clients in the same IP class A/B/C networks as the
local machine. Caution: this may cause
Postfix to "trust" your entire provider's network. Instead, specify
an explicit <a href="postconf.5.html#mynetworks">mynetworks</a> list by hand, as described with the <a href="postconf.5.html#mynetworks">mynetworks</a>
configuration parameter. 

</ul>

</DD>

<DT><a name="myorigin">myorigin</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</DT><DD>


The domain name that locally-posted mail appears to come
from, and that locally posted mail is delivered to. The default,
$<a href="postconf.5.html#myhostname">myhostname</a>, is adequate for small sites. If you run a domain with
multiple machines, you should (1) change this to $<a href="postconf.5.html#mydomain">mydomain</a> and (2)
set up a domain-wide alias database that aliases each user to
user@that.users.mailhost.



Example:


<pre>
<a href="postconf.5.html#myorigin">myorigin</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
</pre>

</DD>

<DT><a name="nested_header_checks">nested_header_checks</a>
(default: $<a href="postconf.5.html#header_checks">header_checks</a>)</DT><DD>


Optional lookup tables for content inspection of non-MIME message
headers in attached messages, as described in the <a href="header_checks.5.html">header_checks(5)</a>
manual page.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="newaliases_path">newaliases_path</a>
(default: see "postconf -d" output)</DT><DD>


Sendmail compatibility feature that specifies the location of the
<a href="newaliases.1.html">newaliases(1)</a> command. This command can be used to rebuild the
<a href="local.8.html">local(8)</a> <a href="aliases.5.html">aliases(5)</a> database.


</DD>

<DT><a name="non_bdb_custom_mapping">non_bdb_custom_mapping</a>
(default: empty)</DT><DD>

 When non-Berkeley-DB migration is enabled, an optional mapping
from a <a href="DATABASE_README.html#types">hash</a>: or <a href="DATABASE_README.html#types">btree</a>: type to a non-Berkeley-DB type. This mapping
takes precedence over the default mapping from <a href="DATABASE_README.html#types">hash</a>: to
$<a href="postconf.5.html#default_database_type">default_database_type</a>, and from <a href="DATABASE_README.html#types">btree</a>: to $<a href="postconf.5.html#default_cache_db_type">default_cache_db_type</a>.


<ul>

<li> Specify a lookup table with a search keys that are a
Berkeley DB type (without ':') or type:name. 

<li> A search key with the form type:name takes precedence
over type (without ':'). 

<li> The lookup result must always be a non-Berkeley-DB type
(without ':') and must not contain a :name. 

<li> The mapping table type must not be hash or btree.

</ul>

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="non_bdb_migration_allow_root_prefixes">non_bdb_migration_allow_root_prefixes</a>
(default: see 'postconf -d <a href="postconf.5.html#non_bdb_migration_allow_root_prefixes">non_bdb_migration_allow_root_prefixes</a>' output)</DT><DD>

 A list of trusted pathname prefixes that must be matched when
the non-Berkeley-DB migration service (<a href="nbdb_reindexd.8.html">nbdb_reindexd(8)</a>) needs to
run <a href="postmap.1.html">postmap(1)</a> or <a href="postalias.1.html">postalias(1)</a> commands with "root" privilege.

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="non_bdb_migration_allow_user_prefixes">non_bdb_migration_allow_user_prefixes</a>
(default: see 'postconf -d <a href="postconf.5.html#non_bdb_migration_allow_user_prefixes">non_bdb_migration_allow_user_prefixes</a>' output)</DT><DD>

 A list of trusted pathname prefixes that must be matched when
the non-Berkeley-DB migration service (<a href="nbdb_reindexd.8.html">nbdb_reindexd(8)</a>) needs to
run <a href="postmap.1.html">postmap(1)</a> or <a href="postalias.1.html">postalias(1)</a> commands with non-root privilege. 

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="non_bdb_migration_level">non_bdb_migration_level</a>
(default: disable)</DT><DD>

 The non-Berkeley-DB migration service level. You are expected to use
the command "<a href="postfix-non-bdb.1.html">postfix non-bdb</a> name-of-level" to correctly
configure the migration service level (see <a href="postfix-non-bdb.1.html">postfix-non-bdb(1)</a>. 

<dl>

<dt>disable</dt>

<dd> Disable all non-Berkeley-DB migration features. See
<a href="NON_BERKELEYDB_README.html#disable">NON_BERKELEYDB_README</a> for possible negative implications
for integration with other software such as mailman. </dd>

<dt>enable-redirect (aliasing)</dt>

<dd> Enable redirection (aliasing) from Berkeley DB hash to
$<a href="postconf.5.html#default_database_type">default_database_type</a>, and from Berkeley DB btree to
$<a href="postconf.5.html#default_cache_db_type">default_cache_db_type</a>, but do not automatically create the new cdb
or lmdb indexed database files that Postfix programs need. See
<a href="NON_BERKELEYDB_README.html#enable-redirect">NON_BERKELEYDB_README</a> for details and limitations.
 </dd>

<dt>enable-reindex</dt>

<dd> In addition to enable-redirect, also create a non-Berkeley-DB
indexed database file when a daemon program wants to access a file
that does not yet exist. This feature uses the <a href="nbdb_reindexd.8.html">nbdb_reindexd(8)</a>
daemon to run <a href="postmap.1.html">postmap(1)</a> or <a href="postalias.1.html">postalias(1)</a>. See
<a href="NON_BERKELEYDB_README.html#enable-reindex">NON_BERKELEYDB_README</a> for details and limitations.


 NOTE: enable-reindex should be used only temporarily to
generate most of the non-Berkeley-DB indexed database files that Postfix
programs need. Leaving this level enabled may expose the system to
privilege-escalation attacks. There are no security concerns for using
enable-redirect. </dd>

</dl>

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="non_bdb_migration_log_redirect">non_bdb_migration_log_redirect</a>
(default: yes)</DT><DD>

 Log actions that redirect from a legacy Berkeley-DB database
type to a non-Berkeley-DB type. 

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="non_bdb_migration_service_name">non_bdb_migration_service_name</a>
(default: nbdb_reindex)</DT><DD>

 The name of a <a href="master.5.html">master.cf</a> service that implements the non-Berkeley-DB
migration service protocol. 

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="non_empty_end_of_header_action">non_empty_end_of_header_action</a>
(default: fix_quietly)</DT><DD>

 How the <a href="cleanup.8.html">cleanup(8)</a> daemon will process a message when the primary
message header is terminated with a non-empty line. 

<dl>

<dt> fix_quietly </dt> <dd> Default behavior: insert
an empty line before the erroneous text. This behavior is backwards
compatible with Postfix ≤ 3.10. </dd>

<dt> add_header </dt><dd> Insert a MIME-Error:
header and an empty line before the erroneous text. 
 Example: 
<pre>
MIME-Error: message header was not terminated by empty line
</pre> </dd>

<dt> reject </dt> <dd> Log the erroneous text and
reject the message content. 
 Example: 
<pre>
queueid reject: mime-error message header was terminated
with non-empty line: erroneous text; from=<sender>
to=<recipient>
</pre>
</dd>

</dl>

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="non_fqdn_reject_code">non_fqdn_reject_code</a>
(default: 504)</DT><DD>


The numerical Postfix SMTP server reply code when a client request
is rejected by the <a href="postconf.5.html#reject_non_fqdn_helo_hostname">reject_non_fqdn_helo_hostname</a>, <a href="postconf.5.html#reject_non_fqdn_sender">reject_non_fqdn_sender</a>
or <a href="postconf.5.html#reject_non_fqdn_recipient">reject_non_fqdn_recipient</a> restriction.


</DD>

<DT><a name="non_smtpd_milters">non_smtpd_milters</a>
(default: empty)</DT><DD>

 A list of Milter (mail filter) applications for new mail that
does not arrive via the Postfix <a href="smtpd.8.html">smtpd(8)</a> server. This includes local
submission via the <a href="sendmail.1.html">sendmail(1)</a> command line, new mail that arrives
via the Postfix <a href="qmqpd.8.html">qmqpd(8)</a> server, and old mail that is re-injected
into the queue with "postsuper -r". Specify space or comma as a
separator. See the <a href="MILTER_README.html">MILTER_README</a> document for details. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="notify_classes">notify_classes</a>
(default: resource, software)</DT><DD>


The list of error classes that are reported to the postmaster. These
postmaster notifications do not replace user notifications. The
default is to report only the most serious problems. The paranoid
may wish to turn on the policy (UCE and mail relaying) and protocol
error (broken mail software) reports.


 NOTE: postmaster notifications may contain confidential information
such as SASL passwords or message content. It is the system
administrator's responsibility to treat such information with care.



The error classes are:


<dl>

<dt>bounce (also implies 2bounce)</dt>

<dd>Send the postmaster copies of the headers of bounced mail, and
send transcripts of SMTP sessions when Postfix rejects mail. The
notification is sent to the address specified with the
<a href="postconf.5.html#bounce_notice_recipient">bounce_notice_recipient</a> configuration parameter (default: postmaster).
</dd>

<dt>2bounce</dt>

<dd>Send undeliverable bounced mail to the postmaster. The notification
is sent to the address specified with the <a href="postconf.5.html#2bounce_notice_recipient">2bounce_notice_recipient</a>
configuration parameter (default: postmaster). </dd>

<dt>data</dt>

<dd>Send the postmaster a transcript of the SMTP session with an
error because a critical data file was unavailable. The notification
is sent to the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a>
configuration parameter (default: postmaster). This feature
is available in Postfix 2.9 and later. </dd>

<dt>delay</dt>

<dd>Send the postmaster copies of the headers of delayed mail (see
<a href="postconf.5.html#delay_warning_time">delay_warning_time</a>). The
notification is sent to the address specified with the
<a href="postconf.5.html#delay_notice_recipient">delay_notice_recipient</a> configuration parameter (default: postmaster).
</dd>

<dt>policy</dt>

<dd>Send the postmaster a transcript of the SMTP session when a
client request was rejected because of (UCE) policy. The notification
is sent to the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a>
configuration parameter (default: postmaster). </dd>

<dt>protocol</dt>

<dd>Send the postmaster a transcript of the SMTP session in case
of client or server protocol errors. The notification is sent to
the address specified with the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration
parameter (default: postmaster). </dd>

<dt>resource</dt>

<dd>Inform the postmaster of mail not delivered due to resource
problems. The notification is sent to the address specified with
the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration parameter (default:
postmaster). </dd>

<dt>software</dt>

<dd>Inform the postmaster of mail not delivered due to software
problems. The notification is sent to the address specified with
the <a href="postconf.5.html#error_notice_recipient">error_notice_recipient</a> configuration parameter (default:
postmaster). </dd>

</dl>


Examples:


<pre>
<a href="postconf.5.html#notify_classes">notify_classes</a> = bounce, delay, policy, protocol, resource, software
<a href="postconf.5.html#notify_classes">notify_classes</a> = 2bounce, resource, software
</pre>

</DD>

<DT><a name="openssl_path">openssl_path</a>
(default: openssl)</DT><DD>


The location of the OpenSSL command line program openssl(1). This
is used by the "<a href="postfix-tls.1.html">postfix tls</a>" command to create private keys,
certificate signing requests, self-signed certificates, and to
compute public key digests for DANE TLSA records. In multi-instance
environments, this parameter is always determined from the configuration
of the default Postfix instance.


 Example: 

<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 # NetBSD pkgsrc:
 <a href="postconf.5.html#openssl_path">openssl_path</a> = /usr/pkg/bin/openssl
 # Local build:
 <a href="postconf.5.html#openssl_path">openssl_path</a> = /usr/local/bin/openssl
</pre>
</blockquote>


This feature is available in Postfix 3.1 and later.


</DD>

<DT><a name="owner_request_special">owner_request_special</a>
(default: yes)</DT><DD>


Enable special treatment for owner-listname entries in the
<a href="aliases.5.html">aliases(5)</a> file, and don't split owner-listname and
listname-request address localparts when the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>
is set to "-". This feature is useful for mailing lists.


</DD>

<DT><a name="parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
(default: see "postconf -d" output)</DT><DD>


A list of Postfix features where the pattern "example.com" also
matches subdomains of example.com,
instead of requiring an explicit ".example.com" pattern. This is
planned backwards compatibility: eventually, all Postfix features
are expected to require explicit ".example.com" style patterns when
you really want to match subdomains.


 The following Postfix feature names are supported. 

<dl>

<dt> Postfix version 1.0 and later</dt>

<dd>
<a href="postconf.5.html#debug_peer_list">debug_peer_list</a>,
<a href="postconf.5.html#fast_flush_domains">fast_flush_domains</a>,
<a href="postconf.5.html#mynetworks">mynetworks</a>,
<a href="postconf.5.html#permit_mx_backup_networks">permit_mx_backup_networks</a>,
<a href="postconf.5.html#relay_domains">relay_domains</a>,
<a href="postconf.5.html#transport_maps">transport_maps</a>
</dd>

<dt> Postfix version 1.1 and later</dt>

<dd>
<a href="postconf.5.html#qmqpd_authorized_clients">qmqpd_authorized_clients</a>,
<a href="SMTPD_ACCESS_README.html">smtpd_access_maps</a>,
</dd>

<dt> Postfix version 2.8 and later </dt>

<dd>
<a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a>
</dd>

<dt> Postfix version 3.0 and later </dt>

<dd>
<a href="postconf.5.html#smtpd_client_event_limit_exceptions">smtpd_client_event_limit_exceptions</a>
</dd>

</dl>

</DD>

<DT><a name="permit_mx_backup_networks">permit_mx_backup_networks</a>
(default: empty)</DT><DD>


Restrict the use of the <a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> SMTP access feature to
only domains whose primary MX hosts match the listed networks.
The parameter value syntax is the same as with the <a href="postconf.5.html#mynetworks">mynetworks</a>
parameter; note, however, that the default value is empty. 

 Pattern matching of domain names is controlled by the presence
or absence of "<a href="postconf.5.html#permit_mx_backup_networks">permit_mx_backup_networks</a>" in the
<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter value. 

</DD>

<DT><a name="pickup_service_name">pickup_service_name</a>
(default: pickup)</DT><DD>


The name of the <a href="pickup.8.html">pickup(8)</a> service. This service picks up local mail
submissions from the Postfix <a href="QSHAPE_README.html#maildrop_queue">maildrop queue</a>.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="pipe_delivery_status_filter">pipe_delivery_status_filter</a>
(default: $<a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a>)</DT><DD>

 Optional filter for the <a href="pipe.8.html">pipe(8)</a> delivery agent to change the
delivery status code or explanatory text of successful or unsuccessful
deliveries. See <a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a> for details. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="plaintext_reject_code">plaintext_reject_code</a>
(default: 450)</DT><DD>


The numerical Postfix SMTP server response code when a request
is rejected by the <a href="postconf.5.html#reject_plaintext_session">reject_plaintext_session</a> restriction.


 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="postlog_service_name">postlog_service_name</a>
(default: postlog)</DT><DD>

 The name of the <a href="postlogd.8.html">postlogd(8)</a> service entry in <a href="master.5.html">master.cf</a>.
This service appends logfile records to the file specified
with the <a href="postconf.5.html#maillog_file">maillog_file</a> parameter. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="postlogd_watchdog_timeout">postlogd_watchdog_timeout</a>
(default: 10s)</DT><DD>

 How much time a <a href="postlogd.8.html">postlogd(8)</a> process may take to process a request
before it is terminated by a built-in watchdog timer. This is a
safety mechanism that prevents <a href="postlogd.8.html">postlogd(8)</a> from becoming non-responsive
due to a bug in Postfix itself or in system software. This limit
cannot be set under 10s. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="postmulti_control_commands">postmulti_control_commands</a>
(default: reload flush)</DT><DD>

 The <a href="postfix.1.html">postfix(1)</a> commands that the <a href="postmulti.1.html">postmulti(1)</a> instance manager
treats as "control" commands, that operate on running instances. For
these commands, disabled instances are skipped. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="postmulti_start_commands">postmulti_start_commands</a>
(default: start)</DT><DD>

 The <a href="postfix.1.html">postfix(1)</a> commands that the <a href="postmulti.1.html">postmulti(1)</a> instance manager treats
as "start" commands. For these commands, disabled instances are "checked"
rather than "started", and failure to "start" a member instance of an
instance group will abort the start-up of later instances. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="postmulti_stop_commands">postmulti_stop_commands</a>
(default: see "postconf -d" output)</DT><DD>

 The <a href="postfix.1.html">postfix(1)</a> commands that the <a href="postmulti.1.html">postmulti(1)</a> instance manager treats
as "stop" commands. For these commands, disabled instances are skipped,
and enabled instances are processed in reverse order. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="postscreen_access_list">postscreen_access_list</a>
(default: <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>)</DT><DD>

 Permanent allow/denylist for remote SMTP client IP addresses.
<a href="postscreen.8.html">postscreen(8)</a> searches this list immediately after a remote SMTP
client connects. Specify a comma- or whitespace-separated list of
commands (in upper or lower case) or lookup tables. The search stops
upon the first command that fires for the client IP address. 

<dl>

<dt> <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a> </dt> <dd> Allowlist the client and
terminate the search if the client IP address matches $<a href="postconf.5.html#mynetworks">mynetworks</a>.
Do not subject the client to any before/after 220 greeting tests.
Pass the connection immediately to a Postfix SMTP server process.
 Pattern matching of domain names is controlled by the presence
or absence of "<a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a>" in the
<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter value. </dd>

<dt> <a href="DATABASE_README.html">type:table</a> </dt> <dd> Query the specified lookup
table. Each table lookup result is an access list, except that
access lists inside a table cannot specify <a href="DATABASE_README.html">type:table</a> entries. 
To discourage the use of hash, btree, etc. tables, there is no
support for substring matching like <a href="smtpd.8.html">smtpd(8)</a>. Use CIDR tables
instead. </dd>

<dt> permit </dt> <dd> Allowlist the client and terminate
the search. Do not subject the client to any before/after 220
greeting tests. Pass the connection immediately to a Postfix SMTP
server process. </dd>

<dt> reject </dt> <dd> Denylist the client and terminate
the search. Subject the client to the action configured with the
<a href="postconf.5.html#postscreen_denylist_action">postscreen_denylist_action</a> configuration parameter. </dd>

<dt> dunno </dt> <dd> All <a href="postscreen.8.html">postscreen(8)</a> access lists
implicitly have this command at the end. When dunno 
is executed inside a lookup table, return from the lookup table and
evaluate the next command. When dunno is executed
outside a lookup table, terminate the search, and subject the client
to the configured before/after 220 greeting tests. </dd>

</dl>

 Example: 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a> = <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>,
 <a href="cidr_table.5.html">cidr</a>:/etc/postfix/postscreen_access.cidr
 # Postfix < 3.6 use <a href="postconf.5.html#postscreen_blacklist_action">postscreen_blacklist_action</a>.
 <a href="postconf.5.html#postscreen_denylist_action">postscreen_denylist_action</a> = enforce
</pre>

<pre>
/etc/postfix/postscreen_access.<a href="cidr_table.5.html">cidr</a>:
 # Rules are evaluated in the order as specified.
 # Denylist 192.168.* except 192.168.0.1.
 192.168.0.1 dunno
 192.168.0.0/16 reject
</pre>

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_allowlist_interfaces">postscreen_allowlist_interfaces</a>
(default: <a href="DATABASE_README.html#types">static</a>:all)</DT><DD>

 A list of local <a href="postscreen.8.html">postscreen(8)</a> server IP addresses where a
non-allowlisted remote SMTP client can obtain <a href="postscreen.8.html">postscreen(8)</a>'s temporary
allowlist status. This status is required before the client can
talk to a Postfix SMTP server process. By default, a client can
obtain <a href="postscreen.8.html">postscreen(8)</a>'s allowlist status on any local <a href="postscreen.8.html">postscreen(8)</a>
server IP address. 

 When <a href="postscreen.8.html">postscreen(8)</a> listens on both primary and backup MX
addresses, the <a href="postconf.5.html#postscreen_allowlist_interfaces">postscreen_allowlist_interfaces</a> parameter can be
configured to give the temporary allowlist status only when a client
connects to a primary MX address. Once a client is allowlisted it
can talk to a Postfix SMTP server on any address. Thus, clients
that connect only to backup MX addresses will never become allowlisted,
and will never be allowed to talk to a Postfix SMTP server process.


 Specify a list of network addresses or network/netmask patterns,
separated by commas and/or whitespace. The netmask specifies the
number of bits in the network part of a host address. Continue long
lines by starting the next line with whitespace. 

 You can also specify "/file/name" or "<a href="DATABASE_README.html">type:table</a>" patterns. A
"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
lookup table is matched when a table entry matches a lookup string
(the lookup result is ignored). 

 The list is matched left to right, and the search stops on the
first match. Specify "!pattern" to exclude an address or network
block from the list. 

 Note: IP version 6 address information must be specified inside
[] in the <a href="postconf.5.html#postscreen_allowlist_interfaces">postscreen_allowlist_interfaces</a> value, and in files
specified with "/file/name". IP version 6 addresses contain the
":" character, and would otherwise be confused with a "<a href="DATABASE_README.html">type:table</a>"
pattern. 

 Example: 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 # Don't allowlist connections to the backup IP address.
 # Postfix < 3.6 use <a href="postconf.5.html#postscreen_whitelist_interfaces">postscreen_whitelist_interfaces</a>.
 <a href="postconf.5.html#postscreen_allowlist_interfaces">postscreen_allowlist_interfaces</a> = !168.100.189.8, <a href="DATABASE_README.html#types">static</a>:all
</pre>

 This feature is available in Postfix 3.6 and later. 

 Available as <a href="postconf.5.html#postscreen_whitelist_interfaces">postscreen_whitelist_interfaces</a> in Postfix 2.9 - 3.5. 

</DD>

<DT><a name="postscreen_bare_newline_action">postscreen_bare_newline_action</a>
(default: ignore)</DT><DD>

 The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client sends
a bare newline character, that is, a newline not preceded by carriage
return. Specify one of the following: 

<dl>

<dt> ignore </dt>

<dd> Ignore the failure of this test. Allow other tests to complete.
Do not repeat this test before the result from some
other test expires.
This option is useful for testing and collecting statistics
without blocking mail permanently. </dd>

<dt> enforce </dt>

<dd> Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects. </dd>

<dt> drop </dt>

<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects. </dd>

</dl>

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_bare_newline_enable">postscreen_bare_newline_enable</a>
(default: no)</DT><DD>

 Enable "bare newline" SMTP protocol tests in the <a href="postscreen.8.html">postscreen(8)</a>
server. These tests are expensive: a remote SMTP client must
disconnect after
it passes the test, before it can talk to a real Postfix SMTP server.


 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_bare_newline_ttl">postscreen_bare_newline_ttl</a>
(default: 30d)</DT><DD>

 The amount of time that <a href="postscreen.8.html">postscreen(8)</a> remembers that a client
IP address passed a "bare newline" SMTP protocol test, before it
address is required to pass that test again. The default
is long because a remote SMTP client must disconnect after it passes
the test,
before it can talk to a real Postfix SMTP server. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_blacklist_action">postscreen_blacklist_action</a>
(default: ignore)</DT><DD>

 Renamed to <a href="postconf.5.html#postscreen_denylist_action">postscreen_denylist_action</a> in Postfix 3.6. 

 This feature is available in Postfix 2.8 - 3.5. 

</DD>

<DT><a name="postscreen_cache_cleanup_interval">postscreen_cache_cleanup_interval</a>
(default: 12h)</DT><DD>

 The amount of time between <a href="postscreen.8.html">postscreen(8)</a> cache cleanup runs.
Cache cleanup increases the load on the cache database and should
therefore not be run frequently. This feature requires that the
cache database supports the "delete" and "sequence" operators.
Specify a zero interval to disable cache cleanup. 

 After each cache cleanup run, the <a href="postscreen.8.html">postscreen(8)</a> daemon logs the
number of entries that were retained and dropped. A cleanup run is
logged as "partial" when the daemon terminates early after "postfix
reload", "postfix stop", or no requests for $<a href="postconf.5.html#max_idle">max_idle</a>
seconds. 

 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_cache_map">postscreen_cache_map</a>
(default: Postfix ≥ 3.11: $<a href="postconf.5.html#default_cache_db_type">default_cache_db_type</a>:$<a href="postconf.5.html#data_directory">data_directory</a>/postscreen_cache; Postfix < 3.11: <a href="DATABASE_README.html#types">btree</a>:$<a href="postconf.5.html#data_directory">data_directory</a>/postscreen_cache)</DT><DD>

 Persistent storage for the <a href="postscreen.8.html">postscreen(8)</a> server decisions. 

 To share a <a href="postscreen.8.html">postscreen(8)</a> cache between multiple <a href="postscreen.8.html">postscreen(8)</a>
instances, use "<a href="postconf.5.html#postscreen_cache_map">postscreen_cache_map</a> = <a href="proxymap.8.html">proxy</a>:<a href="lmdb_table.5.html">lmdb</a>:/path/to/file"
or "<a href="proxymap.8.html">proxy</a>:<a href="DATABASE_README.html#types">btree</a>:/path/to/file".
This requires Postfix version 2.9 or later; earlier <a href="proxymap.8.html">proxymap(8)</a>
implementations don't support cache cleanup. For an alternative
approach see the <a href="memcache_table.5.html">memcache_table(5)</a> manpage. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_cache_retention_time">postscreen_cache_retention_time</a>
(default: 7d)</DT><DD>

 The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will cache an expired
temporary allowlist entry before it is removed. This prevents clients
from being logged as "NEW" just because their cache entry expired
an hour ago. It also prevents the cache from filling up with clients
that passed some deep protocol test once and never came back. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_client_connection_count_limit">postscreen_client_connection_count_limit</a>
(default: $<a href="postconf.5.html#smtpd_client_connection_count_limit">smtpd_client_connection_count_limit</a>)</DT><DD>

 How many simultaneous connections any remote SMTP client is
allowed to have
with the <a href="postscreen.8.html">postscreen(8)</a> daemon. By default, this limit is the same
as with the Postfix SMTP server. Note that the triage process can
take several seconds, with the time spent in <a href="postconf.5.html#postscreen_greet_wait">postscreen_greet_wait</a>
delay, and with the time spent talking to the <a href="postscreen.8.html">postscreen(8)</a> built-in
dummy SMTP protocol engine. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_command_count_limit">postscreen_command_count_limit</a>
(default: 20)</DT><DD>

 The limit on the total number of commands per SMTP session for
<a href="postscreen.8.html">postscreen(8)</a>'s built-in SMTP protocol engine. This SMTP engine
defers or rejects all attempts to deliver mail, therefore there is
no need to enforce separate limits on the number of junk commands
and error commands. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_command_filter">postscreen_command_filter</a>
(default: $<a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a>)</DT><DD>

 A mechanism to transform commands from remote SMTP clients.
See <a href="postconf.5.html#smtpd_command_filter">smtpd_command_filter</a> for further details. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="postscreen_command_time_limit">postscreen_command_time_limit</a>
(default: normal: 300s, <a href="STRESS_README.html">overload</a>: 10s)</DT><DD>

 The time limit to read an entire command line with <a href="postscreen.8.html">postscreen(8)</a>'s
built-in SMTP protocol engine. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_denylist_action">postscreen_denylist_action</a>
(default: ignore)</DT><DD>

 The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client is
permanently denylisted with the <a href="postconf.5.html#postscreen_access_list">postscreen_access_list</a> parameter.
Specify one of the following: 

<dl>

<dt> ignore (default) </dt>

<dd> Ignore this result. Allow other tests to complete. Repeat
this test the next time the client connects.
This option is useful for testing and collecting statistics
without blocking mail. </dd>

<dt> enforce </dt>

<dd> Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects. </dd>

<dt> drop </dt>

<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects. </dd>

</dl>

 This feature is available in Postfix 3.6 and later. 

 Available as <a href="postconf.5.html#postscreen_blacklist_action">postscreen_blacklist_action</a> in Postfix 2.8 - 3.5. 

</DD>

<DT><a name="postscreen_disable_vrfy_command">postscreen_disable_vrfy_command</a>
(default: $<a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a>)</DT><DD>

 Disable the SMTP VRFY command in the <a href="postscreen.8.html">postscreen(8)</a> daemon. See
<a href="postconf.5.html#disable_vrfy_command">disable_vrfy_command</a> for details. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_discard_ehlo_keyword_address_maps">postscreen_discard_ehlo_keyword_address_maps</a>
(default: $<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>)</DT><DD>

 Lookup tables, indexed by the remote SMTP client address, with
case insensitive lists of EHLO keywords (pipelining, starttls, auth,
etc.) that the <a href="postscreen.8.html">postscreen(8)</a> server will not send in the EHLO response
to a remote SMTP client. See <a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a> for details.
The table is not searched by hostname for robustness reasons. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="postscreen_discard_ehlo_keywords">postscreen_discard_ehlo_keywords</a>
(default: $<a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a>)</DT><DD>

 A case insensitive list of EHLO keywords (pipelining, starttls,
auth, etc.) that the <a href="postscreen.8.html">postscreen(8)</a> server will not send in the EHLO
response to a remote SMTP client. See <a href="postconf.5.html#smtpd_discard_ehlo_keywords">smtpd_discard_ehlo_keywords</a>
for details. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="postscreen_dnsbl_action">postscreen_dnsbl_action</a>
(default: ignore)</DT><DD>

The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client's combined
DNSBL score is equal to or greater than a threshold (as defined
with the <a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> and <a href="postconf.5.html#postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a>
parameters). Specify one of the following: 

<dl>

<dt> ignore (default) </dt>

<dd> Ignore the failure of this test. Allow other tests to complete.
Repeat this test the next time the client connects.
This option is useful for testing and collecting statistics
without blocking mail. </dd>

<dt> enforce </dt>

<dd> Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects. </dd>

<dt> drop </dt>

<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects. </dd>

</dl>

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_dnsbl_allowlist_threshold">postscreen_dnsbl_allowlist_threshold</a>
(default: 0)</DT><DD>

 Allow a remote SMTP client to skip "before" and "after 220
greeting" protocol tests, based on its combined DNSBL score as
defined with the <a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> parameter. 

 Specify a negative value to enable this feature. When a client
passes the <a href="postconf.5.html#postscreen_dnsbl_allowlist_threshold">postscreen_dnsbl_allowlist_threshold</a> without having
failed other tests, all pending or disabled tests are flagged as
completed with an expiration time based on the DNS reply TTL.
When a test was already completed, its expiration time is updated
if it was less than the value based on the DNS reply TTL. See
also <a href="postconf.5.html#postscreen_dnsbl_max_ttl">postscreen_dnsbl_max_ttl</a> and <a href="postconf.5.html#postscreen_dnsbl_min_ttl">postscreen_dnsbl_min_ttl</a>. 

 This feature is available in Postfix 3.6 and later. 

 Available as <a href="postconf.5.html#postscreen_dnsbl_whitelist_threshold">postscreen_dnsbl_whitelist_threshold</a> in Postfix 2.11
- 3.5. 

</DD>

<DT><a name="postscreen_dnsbl_max_ttl">postscreen_dnsbl_max_ttl</a>
(default: ${<a href="postconf.5.html#postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>?{$<a href="postconf.5.html#postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>}:{1}}h)</DT><DD>

 The maximum amount of time that <a href="postscreen.8.html">postscreen(8)</a> remembers that a
client IP address passed a DNS-based reputation test, before it is
required to pass that test again. If the DNS
reply specifies a shorter TTL value, that value will be used unless
it would be smaller than <a href="postconf.5.html#postscreen_dnsbl_min_ttl">postscreen_dnsbl_min_ttl</a>. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours). 

 This feature is available in Postfix 3.1. The default setting
is backwards-compatible with older Postfix versions. 

</DD>

<DT><a name="postscreen_dnsbl_min_ttl">postscreen_dnsbl_min_ttl</a>
(default: 60s)</DT><DD>

 The minimum amount of time that <a href="postscreen.8.html">postscreen(8)</a> remembers that a
client IP address passed a DNS-based reputation test, before it
is required to pass that test again. If the DNS
reply specifies a larger TTL value, that value will be used unless
it would be larger than <a href="postconf.5.html#postscreen_dnsbl_max_ttl">postscreen_dnsbl_max_ttl</a>. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 3.1. 

</DD>

<DT><a name="postscreen_dnsbl_reply_map">postscreen_dnsbl_reply_map</a>
(default: empty)</DT><DD>

 A mapping from an actual DNSBL domain name which includes a secret
password, to the DNSBL domain name that postscreen will reply with
when it rejects mail. When no mapping is found, the actual DNSBL
domain will be used. 

 For maximal stability it is best to use a file that is read
into memory such as <a href="pcre_table.5.html">pcre</a>:, <a href="regexp_table.5.html">regexp</a>: or <a href="DATABASE_README.html#types">texthash</a>: (<a href="DATABASE_README.html#types">texthash</a>: is similar
to <a href="DATABASE_README.html#types">hash</a>:, except a) there is no need to run <a href="postmap.1.html">postmap(1)</a> before the
file can be used, and b) <a href="DATABASE_README.html#types">texthash</a>: does not detect changes after
the file is read). 

 Example: 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#postscreen_dnsbl_reply_map">postscreen_dnsbl_reply_map</a> = <a href="DATABASE_README.html#types">texthash</a>:/etc/postfix/dnsbl_reply
</pre>

<pre>
/etc/postfix/dnsbl_reply:
 secret.zen.spamhaus.org zen.spamhaus.org
</pre>

 NOTE: This feature differs from the Postfix SMTP server's
<a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> feature, where 1) the table search key includes the
optional "=address-filter", and where 2) the lookup result
contains free text with $name variables. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_dnsbl_sites">postscreen_dnsbl_sites</a>
(default: empty)</DT><DD>

Optional list of patterns with DNS allow/denylist domains, filters
and weight
factors. When the list is non-empty, the <a href="dnsblog.8.html">dnsblog(8)</a> daemon will
query these domains with the reversed IP addresses of remote SMTP
clients,
and <a href="postscreen.8.html">postscreen(8)</a> will update an SMTP client's DNSBL score with
each non-error reply as described below. 

 NOTE: Always respect the usage policies of reputation services.
Avoid public or ISP resolvers, unless the queries use your unique
API key. 

 Caution: when postscreen rejects mail, its SMTP response contains
the DNSBL
domain name. Use the <a href="postconf.5.html#postscreen_dnsbl_reply_map">postscreen_dnsbl_reply_map</a> feature to hide
"password" information in DNSBL domain names. 

 When a client's score is equal to or greater than the threshold
specified with <a href="postconf.5.html#postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a>, <a href="postscreen.8.html">postscreen(8)</a> can drop
the connection with the remote SMTP client. 

 Specify a list of domain=filter*weight patterns, separated by
comma or whitespace. 

<ul>

<li> When a pattern specifies no "=filter", <a href="postscreen.8.html">postscreen(8)</a> will
use any non-error DNSBL query result. Otherwise, <a href="postscreen.8.html">postscreen(8)</a>
will use only DNSBL
query results that match the filter. The filter has the form d.d.d.d,
where each d is a number, or a pattern inside [] that contains one
or more ";"-separated numbers or number..number ranges. 

<li> When a pattern specifies no "*weight", the weight of the
pattern is 1. Otherwise, the weight must be an integral number.
Specify a negative number for allowlisting. 

<li> When a pattern matches one or more DNSBL query results,
<a href="postscreen.8.html">postscreen(8)</a> adds that pattern's weight once to the remote SMTP
client's DNSBL score. 

</ul>

 Examples: 

 To use example.com as a high-confidence blocklist, and to
block mail with example.net and example.org only when both agree:


<pre>
<a href="postconf.5.html#postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a> = 2
<a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> = example.com*2, example.net, example.org
</pre>

 To filter only DNSBL replies containing 127.0.0.4: 

<pre>
<a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a> = example.com=127.0.0.4
</pre>

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_dnsbl_threshold">postscreen_dnsbl_threshold</a>
(default: 1)</DT><DD>

 The inclusive lower bound for blocking a remote SMTP client, based on
its combined DNSBL score as defined with the <a href="postconf.5.html#postscreen_dnsbl_sites">postscreen_dnsbl_sites</a>
parameter. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_dnsbl_timeout">postscreen_dnsbl_timeout</a>
(default: 10s)</DT><DD>

 The time limit for DNSBL or DNSWL lookups. This is separate from
the timeouts in the <a href="dnsblog.8.html">dnsblog(8)</a> daemon which are defined by system
resolver(3) routines. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 3.0. 

</DD>

<DT><a name="postscreen_dnsbl_ttl">postscreen_dnsbl_ttl</a>
(default: 1h)</DT><DD>

 The amount of time that <a href="postscreen.8.html">postscreen(8)</a> remembers that a client
IP address passed a DNS-based reputation test, before it is required
to pass that test again. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is h (hours). 

 This feature is available in Postfix 2.8-3.0. It was
replaced by <a href="postconf.5.html#postscreen_dnsbl_max_ttl">postscreen_dnsbl_max_ttl</a> in Postfix 3.1. 

</DD>

<DT><a name="postscreen_dnsbl_whitelist_threshold">postscreen_dnsbl_whitelist_threshold</a>
(default: 0)</DT><DD>

 Renamed to <a href="postconf.5.html#postscreen_dnsbl_allowlist_threshold">postscreen_dnsbl_allowlist_threshold</a> in Postfix 3.6. 

 This feature is available in Postfix 2.11 - 3.5. 

</DD>

<DT><a name="postscreen_enforce_tls">postscreen_enforce_tls</a>
(default: $<a href="postconf.5.html#smtpd_enforce_tls">smtpd_enforce_tls</a>)</DT><DD>

 Mandatory TLS: announce STARTTLS support to remote SMTP clients, and
require that clients use TLS encryption. See smtpd_postscreen_enforce_tls
for details. 

 This feature is available in Postfix 2.8 and later.
Preferably, use <a href="postconf.5.html#postscreen_tls_security_level">postscreen_tls_security_level</a> instead. 

</DD>

<DT><a name="postscreen_expansion_filter">postscreen_expansion_filter</a>
(default: see "postconf -d" output)</DT><DD>

 List of characters that are permitted in <a href="postconf.5.html#postscreen_reject_footer">postscreen_reject_footer</a>
attribute expansions. See <a href="postconf.5.html#smtpd_expansion_filter">smtpd_expansion_filter</a> for further
details. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="postscreen_forbidden_commands">postscreen_forbidden_commands</a>
(default: $<a href="postconf.5.html#smtpd_forbidden_commands">smtpd_forbidden_commands</a>)</DT><DD>

 List of commands that the <a href="postscreen.8.html">postscreen(8)</a> server considers in
violation of the SMTP protocol. See <a href="postconf.5.html#smtpd_forbidden_commands">smtpd_forbidden_commands</a> for
syntax, and <a href="postconf.5.html#postscreen_non_smtp_command_action">postscreen_non_smtp_command_action</a> for possible actions.


 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_greet_action">postscreen_greet_action</a>
(default: ignore)</DT><DD>

The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client speaks
before its turn within the time specified with the <a href="postconf.5.html#postscreen_greet_wait">postscreen_greet_wait</a>
parameter. Specify one of the following: 

<dl>

<dt> ignore (default) </dt>

<dd> Ignore the failure of this test. Allow other tests to complete.
Repeat this test the next time the client connects.
This option is useful for testing and collecting statistics
without blocking mail. </dd>

<dt> enforce </dt>

<dd> Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects. </dd>

<dt> drop </dt>

<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects. </dd>

</dl>

 In either case, <a href="postscreen.8.html">postscreen(8)</a> will not allowlist the remote SMTP client
IP address. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_greet_banner">postscreen_greet_banner</a>
(default: $<a href="postconf.5.html#smtpd_banner">smtpd_banner</a>)</DT><DD>

 The text in the optional "220-text..." server
response that
<a href="postscreen.8.html">postscreen(8)</a> sends ahead of the real Postfix SMTP server's "220
text..." response, in an attempt to confuse bad SMTP clients so
that they speak before their turn (pre-greet). Specify an empty
value to disable this feature. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_greet_ttl">postscreen_greet_ttl</a>
(default: 1d)</DT><DD>

 The amount of time that <a href="postscreen.8.html">postscreen(8)</a> remembers that a client
IP address passed a PREGREET test, before it is required to pass
that test again. The default is relatively short, because
a good client can immediately talk to a real Postfix SMTP server. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_greet_wait">postscreen_greet_wait</a>
(default: normal: 6s, <a href="STRESS_README.html">overload</a>: 2s)</DT><DD>

 The amount of time that <a href="postscreen.8.html">postscreen(8)</a> will wait for an SMTP
client to send a command before its turn, and for DNS blocklist
lookup results to arrive (default: up to 2 seconds under stress,
up to 6 seconds otherwise). 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_helo_required">postscreen_helo_required</a>
(default: $<a href="postconf.5.html#smtpd_helo_required">smtpd_helo_required</a>)</DT><DD>

 Require that a remote SMTP client sends HELO or EHLO before
commencing a MAIL transaction. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_non_smtp_command_action">postscreen_non_smtp_command_action</a>
(default: drop)</DT><DD>

 The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client sends
non-SMTP commands as specified with the <a href="postconf.5.html#postscreen_forbidden_commands">postscreen_forbidden_commands</a>
parameter. Specify one of the following: 

<dl>

<dt> ignore </dt>

<dd> Ignore the failure of this test. Allow other tests to complete.
Do not repeat this test before the result from some
other test expires.
This option is useful for testing and collecting statistics
without blocking mail permanently. </dd>

<dt> enforce </dt>

<dd> Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects. </dd>

<dt> drop </dt>

<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects. This action is the
same as with the Postfix SMTP server's <a href="postconf.5.html#smtpd_forbidden_commands">smtpd_forbidden_commands</a>
feature. </dd>

</dl>

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_non_smtp_command_enable">postscreen_non_smtp_command_enable</a>
(default: no)</DT><DD>

 Enable "non-SMTP command" tests in the <a href="postscreen.8.html">postscreen(8)</a> server. These
tests are expensive: a client must disconnect after it passes the
test, before it can talk to a real Postfix SMTP server. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_non_smtp_command_ttl">postscreen_non_smtp_command_ttl</a>
(default: 30d)</DT><DD>

 The amount of time that <a href="postscreen.8.html">postscreen(8)</a> remembers that a client
IP address passed a "non_smtp_command" SMTP protocol test, before
it is required to pass that test again. The default
is long because a client must disconnect after it passes the test,
before it can talk to a real Postfix SMTP server. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_pipelining_action">postscreen_pipelining_action</a>
(default: enforce)</DT><DD>

 The action that <a href="postscreen.8.html">postscreen(8)</a> takes when a remote SMTP client
sends
multiple commands instead of sending one command and waiting for
the server to respond. Specify one of the following: 

<dl>

<dt> ignore </dt>

<dd> Ignore the failure of this test. Allow other tests to complete.
Do not repeat this test before the result from some
other test expires.
This option is useful for testing and collecting statistics
without blocking mail permanently. </dd>

<dt> enforce </dt>

<dd> Allow other tests to complete. Reject attempts to deliver mail
with a 550 SMTP reply, and log the helo/sender/recipient information.
Repeat this test the next time the client connects. </dd>

<dt> drop </dt>

<dd> Drop the connection immediately with a 521 SMTP reply. Repeat
this test the next time the client connects. </dd>

</dl>

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_pipelining_enable">postscreen_pipelining_enable</a>
(default: no)</DT><DD>

 Enable "pipelining" SMTP protocol tests in the <a href="postscreen.8.html">postscreen(8)</a>
server. These tests are expensive: a good client must disconnect
after it passes the test, before it can talk to a real Postfix SMTP
server. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_pipelining_ttl">postscreen_pipelining_ttl</a>
(default: 30d)</DT><DD>

 The amount of time that <a href="postscreen.8.html">postscreen(8)</a> remembers that a client
IP address passed a "pipelining" SMTP protocol test, before it is
required to pass that test again. The default is
long because a good client must disconnect after it passes the test,
before it can talk to a real Postfix SMTP server. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_post_queue_limit">postscreen_post_queue_limit</a>
(default: $<a href="postconf.5.html#default_process_limit">default_process_limit</a>)</DT><DD>

 The number of clients that can be waiting for service from a
real Postfix SMTP server process. When this queue is full, all
clients will
receive a 421 response. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_pre_queue_limit">postscreen_pre_queue_limit</a>
(default: $<a href="postconf.5.html#default_process_limit">default_process_limit</a>)</DT><DD>

 The number of non-allowlisted clients that can be waiting for
a decision whether they will receive service from a real Postfix
SMTP server
process. When this queue is full, all non-allowlisted clients will
receive a 421 response. 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_reject_footer">postscreen_reject_footer</a>
(default: $<a href="postconf.5.html#smtpd_reject_footer">smtpd_reject_footer</a>)</DT><DD>

 Optional information that is appended after a 4XX or 5XX
<a href="postscreen.8.html">postscreen(8)</a> server
response. See <a href="postconf.5.html#smtpd_reject_footer">smtpd_reject_footer</a> for further details. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="postscreen_reject_footer_maps">postscreen_reject_footer_maps</a>
(default: $<a href="postconf.5.html#smtpd_reject_footer_maps">smtpd_reject_footer_maps</a>)</DT><DD>

 Optional lookup table for information that is appended after a 4XX
or 5XX <a href="postscreen.8.html">postscreen(8)</a> server response. See <a href="postconf.5.html#smtpd_reject_footer_maps">smtpd_reject_footer_maps</a> for
further details. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="postscreen_tls_security_level">postscreen_tls_security_level</a>
(default: $<a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a>)</DT><DD>

 The SMTP TLS security level for the <a href="postscreen.8.html">postscreen(8)</a> server; when
a non-empty value is specified, this overrides the obsolete parameters
<a href="postconf.5.html#postscreen_use_tls">postscreen_use_tls</a> and <a href="postconf.5.html#postscreen_enforce_tls">postscreen_enforce_tls</a>. See <a href="postconf.5.html#smtpd_tls_security_level">smtpd_tls_security_level</a>
for details. 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="postscreen_upstream_proxy_protocol">postscreen_upstream_proxy_protocol</a>
(default: empty)</DT><DD>

 The name of the proxy protocol used by an optional before-postscreen
proxy agent. When a proxy agent is used, this protocol conveys local
and remote address and port information. Specify
"<a href="postconf.5.html#postscreen_upstream_proxy_protocol">postscreen_upstream_proxy_protocol</a> = haproxy" to enable the haproxy
protocol; version 2 is supported with Postfix 3.5 and later. 

 This feature is available in Postfix 2.10 and later. 

</DD>

<DT><a name="postscreen_upstream_proxy_timeout">postscreen_upstream_proxy_timeout</a>
(default: 5s)</DT><DD>

 The time limit for the proxy protocol specified with the
<a href="postconf.5.html#postscreen_upstream_proxy_protocol">postscreen_upstream_proxy_protocol</a> parameter. 

 This feature is available in Postfix 2.10 and later. 

</DD>

<DT><a name="postscreen_use_tls">postscreen_use_tls</a>
(default: $<a href="postconf.5.html#smtpd_use_tls">smtpd_use_tls</a>)</DT><DD>

 Opportunistic TLS: announce STARTTLS support to remote SMTP clients,
but do not require that clients use TLS encryption. 

 This feature is available in Postfix 2.8 and later.
Preferably, use <a href="postconf.5.html#postscreen_tls_security_level">postscreen_tls_security_level</a> instead. 

</DD>

<DT><a name="postscreen_watchdog_timeout">postscreen_watchdog_timeout</a>
(default: 10s)</DT><DD>

 How much time a <a href="postscreen.8.html">postscreen(8)</a> process may take to respond to
a remote SMTP client command or to perform a cache operation before it
is terminated by a built-in watchdog timer. This is a safety
mechanism that prevents <a href="postscreen.8.html">postscreen(8)</a> from becoming non-responsive
due to a bug in Postfix itself or in system software. To avoid
false alarms and unnecessary cache corruption this limit cannot be
set under 10s. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.8. 

</DD>

<DT><a name="postscreen_whitelist_interfaces">postscreen_whitelist_interfaces</a>
(default: <a href="DATABASE_README.html#types">static</a>:all)</DT><DD>

 Renamed to <a href="postconf.5.html#postscreen_allowlist_interfaces">postscreen_allowlist_interfaces</a> in Postfix 3.6. 

 This feature is available in Postfix 2.9 - 3.5. 

</DD>

<DT><a name="prepend_delivered_header">prepend_delivered_header</a>
(default: command, file, forward)</DT><DD>

 The message delivery contexts where the Postfix <a href="local.8.html">local(8)</a> delivery
agent prepends a Delivered-To: message header with the address
that the mail was delivered to. This information is used for mail
delivery loop detection. 


By default, the Postfix local delivery agent prepends a Delivered-To:
header when forwarding mail and when delivering to file (mailbox)
and command. Turning off the Delivered-To: header when forwarding
mail is not recommended.



Specify zero or more of forward, file, or command.



Example:


<pre>
<a href="postconf.5.html#prepend_delivered_header">prepend_delivered_header</a> = forward
</pre>

</DD>

<DT><a name="process_id">process_id</a>
(read-only)</DT><DD>


The process ID of a Postfix command or daemon process.


</DD>

<DT><a name="process_id_directory">process_id_directory</a>
(default: pid)</DT><DD>


The location of Postfix PID files relative to $<a href="postconf.5.html#queue_directory">queue_directory</a>.
This is a read-only parameter.


</DD>

<DT><a name="process_name">process_name</a>
(read-only)</DT><DD>


The process name of a Postfix command or daemon process.


</DD>

<DT><a name="propagate_unmatched_extensions">propagate_unmatched_extensions</a>
(default: canonical, virtual)</DT><DD>


What address lookup tables copy an address extension from the lookup
key to the lookup result.



For example, with a <a href="virtual.5.html">virtual(5)</a> mapping of "joe@example.com =>
joe.user@example.net", the address "joe+foo@example.com"
would rewrite to "joe.user+foo@example.net".



Specify zero or more of canonical, virtual, alias,
forward, include or generic. These cause
address extension
propagation with <a href="canonical.5.html">canonical(5)</a>, <a href="virtual.5.html">virtual(5)</a>, and <a href="aliases.5.html">aliases(5)</a> maps,
with <a href="local.8.html">local(8)</a> .forward and :include: file lookups, and with <a href="smtp.8.html">smtp(8)</a>
generic maps, respectively. 


Note: enabling this feature for types other than canonical
and virtual is likely to cause problems when mail is forwarded
to other sites, especially with mail that is sent to a mailing list
exploder address.



Examples:


<pre>
<a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual, alias,
 forward, include
<a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a> = canonical, virtual
</pre>

</DD>

<DT><a name="proxy_interfaces">proxy_interfaces</a>
(default: empty)</DT><DD>


The remote network interface addresses that this mail system receives mail
on by way of a proxy or network address translation unit.



This feature is available in Postfix 2.0 and later.


 You must specify your "outside" proxy/NAT addresses when your
system is a backup MX host for other domains, otherwise mail delivery
loops will happen when the primary MX host is down. 


Example:


<pre>
<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a> = 1.2.3.4
</pre>

</DD>

<DT><a name="proxy_read_maps">proxy_read_maps</a>
(default: see "postconf -d" output)</DT><DD>


The lookup tables that the <a href="proxymap.8.html">proxymap(8)</a> server is allowed to
access for the read-only service.



Specify zero or more "type:name" lookup tables, separated by
whitespace or comma.
Table references that don't begin with <a href="proxymap.8.html">proxy</a>: are ignored.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="proxy_write_maps">proxy_write_maps</a>
(default: see "postconf -d" output)</DT><DD>

 The lookup tables that the <a href="proxymap.8.html">proxymap(8)</a> server is allowed to
access for the read-write service. Postfix-owned local database
files should be stored under the Postfix-owned <a href="postconf.5.html#data_directory">data_directory</a>.
Table references that don't begin with <a href="proxymap.8.html">proxy</a>: are ignored. 


This feature is available in Postfix 2.5 and later.


</DD>

<DT><a name="proxymap_service_name">proxymap_service_name</a>
(default: proxymap)</DT><DD>

 The name of the proxymap read-only table lookup service. This
service is normally implemented by the <a href="proxymap.8.html">proxymap(8)</a> daemon. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="proxywrite_service_name">proxywrite_service_name</a>
(default: proxywrite)</DT><DD>

 The name of the proxywrite read-write table lookup service.
This service is normally implemented by the <a href="proxymap.8.html">proxymap(8)</a> daemon.


 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="qmgr_clog_warn_time">qmgr_clog_warn_time</a>
(default: 300s)</DT><DD>


The minimal delay between warnings that a specific destination is
clogging up the Postfix <a href="QSHAPE_README.html#active_queue">active queue</a>. Specify 0 to disable.


 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


This feature is enabled with the <a href="postconf.5.html#helpful_warnings">helpful_warnings</a> parameter.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="qmgr_daemon_timeout">qmgr_daemon_timeout</a>
(default: 1000s)</DT><DD>

 How much time a Postfix queue manager process may take to handle
a request before it is terminated by a built-in watchdog timer.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="qmgr_fudge_factor">qmgr_fudge_factor</a>
(default: 100)</DT><DD>


Obsolete feature: the percentage of delivery resources that a busy
mail system will use up for delivery of a large mailing list
message.



This feature exists only in the <a href="qmgr.8.html">oqmgr(8)</a> old queue manager. The
current queue manager solves the problem in a better way.


</DD>

<DT><a name="qmgr_ipc_timeout">qmgr_ipc_timeout</a>
(default: 60s)</DT><DD>

 The time limit for the queue manager to send or receive information
over an internal communication channel. The purpose is to break
out of deadlock situations. If the time limit is exceeded the
software either retries or aborts the operation. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="qmgr_message_active_limit">qmgr_message_active_limit</a>
(default: 20000)</DT><DD>


The maximal number of messages in the <a href="QSHAPE_README.html#active_queue">active queue</a>.


</DD>

<DT><a name="qmgr_message_recipient_limit">qmgr_message_recipient_limit</a>
(default: 20000)</DT><DD>

 The maximal number of recipients held in memory by the Postfix
queue manager, and the maximal size of the short-term,
in-memory "dead" destination status cache. 

</DD>

<DT><a name="qmgr_message_recipient_minimum">qmgr_message_recipient_minimum</a>
(default: 10)</DT><DD>


The minimal number of in-memory recipients for any message. This
takes priority over any other in-memory recipient limits (i.e.,
the global <a href="postconf.5.html#qmgr_message_recipient_limit">qmgr_message_recipient_limit</a> and the per transport
_recipient_limit) if necessary. The minimum value allowed for this
parameter is 1.


</DD>

<DT><a name="qmqpd_authorized_clients">qmqpd_authorized_clients</a>
(default: empty)</DT><DD>


What remote QMQP clients are allowed to connect to the Postfix QMQP
server port.



By default, no client is allowed to use the service. This is
because the QMQP server will relay mail to any destination.



Specify a list of client patterns. A list pattern specifies a host
name, a domain name, an internet address, or a network/mask pattern,
where the mask specifies the number of bits in the network part.
When a pattern specifies a file name, its contents are substituted
for the file name; when a pattern is a "<a href="DATABASE_README.html">type:table</a>" table specification,
table lookup is used instead. An IPv6 address must be enclosed in
<tt>[]</tt>. 


Patterns are separated by whitespace and/or commas. In order to
reverse the result, precede a pattern with an
exclamation point (!). The form "!/file/name" is supported only
in Postfix version 2.4 and later.


 Pattern matching of domain names is controlled by the presence
or absence of "<a href="postconf.5.html#qmqpd_authorized_clients">qmqpd_authorized_clients</a>" in the
<a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a> parameter value. 


Example:


<pre>
<a href="postconf.5.html#qmqpd_authorized_clients">qmqpd_authorized_clients</a> = !192.168.0.1, 192.168.0.0/24
</pre>

</DD>

<DT><a name="qmqpd_client_port_logging">qmqpd_client_port_logging</a>
(default: no)</DT><DD>

 Enable logging of the remote QMQP client port in addition to
the hostname and IP address. The logging format is "host[address]:port".


 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="qmqpd_error_delay">qmqpd_error_delay</a>
(default: 1s)</DT><DD>


How long the Postfix QMQP server will pause before sending a negative
reply to the remote QMQP client. The purpose is to slow down confused
or malicious clients.


 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="qmqpd_timeout">qmqpd_timeout</a>
(default: 300s)</DT><DD>


The time limit for sending or receiving information over the network.
If a read or write operation blocks for more than $<a href="postconf.5.html#qmqpd_timeout">qmqpd_timeout</a>
seconds the Postfix QMQP server gives up and disconnects.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="queue_directory">queue_directory</a>
(default: see "postconf -d" output)</DT><DD>


The location of the Postfix top-level queue directory. This is the
root directory of Postfix daemon processes that run chrooted.


</DD>

<DT><a name="queue_file_attribute_count_limit">queue_file_attribute_count_limit</a>
(default: 100)</DT><DD>


The maximal number of (name=value) attributes that may be stored
in a Postfix queue file. The limit is enforced by the <a href="cleanup.8.html">cleanup(8)</a>
server.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="queue_minfree">queue_minfree</a>
(default: 0)</DT><DD>


The minimal amount of free space in bytes in the queue file system
that is needed to receive mail. This is currently used by the
Postfix SMTP server to decide if it will accept any mail at all.



By default, the Postfix SMTP server rejects MAIL FROM commands when
the amount of free space is less than 1.5*$<a href="postconf.5.html#message_size_limit">message_size_limit</a>
(Postfix version 2.1 and later).
To specify a higher minimum free space limit, specify a <a href="postconf.5.html#queue_minfree">queue_minfree</a>
value that is at least 1.5*$<a href="postconf.5.html#message_size_limit">message_size_limit</a>.



With Postfix versions 2.0 and earlier, a <a href="postconf.5.html#queue_minfree">queue_minfree</a> value of
zero means there is no minimum required amount of free space.


</DD>

<DT><a name="queue_run_delay">queue_run_delay</a>
(default: 300s)</DT><DD>


The time between <a href="QSHAPE_README.html#deferred_queue">deferred queue</a> scans by the queue manager;
prior to Postfix 2.4 the default value was 1000s.


 This parameter should be set less than or equal to
$<a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a>. See also $<a href="postconf.5.html#maximal_backoff_time">maximal_backoff_time</a>. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="queue_service_name">queue_service_name</a>
(default: qmgr)</DT><DD>


The name of the <a href="qmgr.8.html">qmgr(8)</a> service. This service manages the Postfix
queue and schedules delivery requests.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="rbl_reply_maps">rbl_reply_maps</a>
(default: empty)</DT><DD>


Optional lookup tables with RBL or RHSBL response templates. The
table search key is the reject_rbl_* or reject_rhsbl_* argument,
including any optional "=address-filter". With Postfix 3.10
and later, if the result is "not found" and the search key has the
form domain=address-filter, then <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> will also
search with the domain. 

 By default, Postfix uses the
template as specified with the <a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a> configuration
parameter. See there for a discussion of the response template
syntax.


 Example: 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/rbl_reply
 <a href="postconf.5.html#smtpd_recipient_restrictions">smtpd_recipient_restrictions</a> =
 <a href="postconf.5.html#permit_mynetworks">permit_mynetworks</a>,
 <a href="postconf.5.html#reject_rbl_client">reject_rbl_client</a> secret.zen.dq.spamhaus.net=127.0.0.[2..11],
 ...
 
/etc/postfix/rbl_reply:
 # See https://www.postfix.org/postconf.5.html#<a href="postconf.5.html#default_rbl_reply">default_rbl_reply</a>
 # for the definition of the $client_address and $rbl_class etc.
 # variables.
 secret.zen.dq.spamhaus.net=127.0.0.[2..11]
 554 $rbl_class $rbl_what blocked using ZEN - see <a href="https://www.spamhaus.org/query/ip/$client_address">https://www.spamhaus.org/query/ip/$client_address</a> for details
</pre>

<pre>
 # Postfix ≥ 3.10: if a search key domain=address-filter
 # is not found, then <a href="postconf.5.html#rbl_reply_maps">rbl_reply_maps</a> will also search with the
 # domain.
 secret.zen.dq.spamhaus.net
 554 $rbl_class $rbl_what blocked using ZEN - see <a href="https://www.spamhaus.org/query/ip/$client_address">https://www.spamhaus.org/query/ip/$client_address</a> for details
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 


NOTE: This feature differs from <a href="postconf.5.html#postscreen_dnsbl_reply_map">postscreen_dnsbl_reply_map</a> where
the table search key is only a domain name (no "=address-filter",
no "*weight" factor) and where the lookup result
should be only a domain name (no free text, no $name variables).


 Execute the command "postmap /etc/postfix/rbl_reply" after you
change the rbl_reply file, to (re)build a default-type indexed file.
Execute "postmap type:/etc/postfix/rbl_reply" to specify an
explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 


This feature is available in Postfix 2.0 and later.
The "=address-filter" feature is available in Postfix 2.8 and later.


</DD>

<DT><a name="readme_directory">readme_directory</a>
(default: see "postconf -d" output)</DT><DD>


The location of Postfix README files that describe how to build,
configure or operate a specific Postfix subsystem or feature.


</DD>

<DT><a name="receive_override_options">receive_override_options</a>
(default: empty)</DT><DD>

 Enable or disable recipient validation, built-in content
filtering, or address mapping. Typically, these are specified in
<a href="master.5.html">master.cf</a> as command-line arguments for the <a href="smtpd.8.html">smtpd(8)</a>, <a href="qmqpd.8.html">qmqpd(8)</a> or
<a href="pickup.8.html">pickup(8)</a> daemons. 

 Specify zero or more of the following options. The options
override <a href="postconf.5.html">main.cf</a> settings and are either implemented by <a href="smtpd.8.html">smtpd(8)</a>,
<a href="qmqpd.8.html">qmqpd(8)</a>, or <a href="pickup.8.html">pickup(8)</a> themselves, or they are forwarded to the
cleanup server. 

<dl>

<dt><a name="no_unknown_recipient_checks">no_unknown_recipient_checks</a></dt>

<dd>Do not try to reject unknown recipients (SMTP server only).
This is typically specified AFTER an external content filter.
</dd>

<dt><a name="no_address_mappings">no_address_mappings</a></dt>

<dd>Disable canonical address mapping, virtual alias map expansion,
address masquerading, and automatic BCC (blind carbon-copy)
recipients. This is typically specified BEFORE an external content
filter. </dd>

<dt><a name="no_header_body_checks">no_header_body_checks</a></dt>

<dd>Disable header/body_checks. This is typically specified AFTER
an external content filter. </dd>

<dt><a name="no_milters">no_milters</a></dt>

<dd>Disable Milter (mail filter) applications. This is typically
specified AFTER an external content filter. </dd>

</dl>


Note: when the "BEFORE content filter" <a href="postconf.5.html#receive_override_options">receive_override_options</a>
setting is specified in the <a href="postconf.5.html">main.cf</a> file, specify the "AFTER content
filter" <a href="postconf.5.html#receive_override_options">receive_override_options</a> setting in <a href="master.5.html">master.cf</a> (and vice
versa).



Examples:


<pre>
<a href="postconf.5.html#receive_override_options">receive_override_options</a> =
 <a href="postconf.5.html#no_unknown_recipient_checks">no_unknown_recipient_checks</a>, <a href="postconf.5.html#no_header_body_checks">no_header_body_checks</a>
<a href="postconf.5.html#receive_override_options">receive_override_options</a> = <a href="postconf.5.html#no_address_mappings">no_address_mappings</a>
</pre>


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="recipient_bcc_maps">recipient_bcc_maps</a>
(default: empty)</DT><DD>


Optional BCC (blind carbon-copy) address lookup tables, indexed by
envelope recipient address. The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix.



Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.



The table search order is as follows:


<ul>

<li> Look up the "user+extension@domain.tld" address including the
optional address extension.

<li> Look up the "user@domain.tld" address without the optional
address extension.

<li> Look up the "user+extension" address local part when the
recipient domain equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "user" address local part when the recipient domain
equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "@domain.tld" part.

</ul>


Note: with Postfix 2.3 and later the BCC address is added as if it
was specified with NOTIFY=NONE. The sender will not be notified
when the BCC address is undeliverable, as long as all down-stream
software implements <a href="https://tools.ietf.org/html/rfc3461">RFC 3461</a>.



Note: with Postfix 2.2 and earlier the sender will unconditionally
be notified when the BCC address is undeliverable.


 Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
after Postfix forwards mail internally, or after Postfix generates
mail itself. 

 Note: automatic BCC recipients are subject to address
canonicalization (add missing domain), <a href="postconf.5.html#canonical_maps">canonical_maps</a>, <a href="postconf.5.html#masquerade_domains">masquerade_domains</a>,
and <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>. 


Example:


<pre>
<a href="postconf.5.html#recipient_bcc_maps">recipient_bcc_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/recipient_bcc
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/recipient_bcc" after
you change the recipient_bcc file, to (re)build a default-type indexed
file. Execute "postmap type:/etc/postfix/recipient_bcc" to
specify an explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="recipient_canonical_classes">recipient_canonical_classes</a>
(default: envelope_recipient, header_recipient)</DT><DD>

 What addresses are subject to <a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> address
mapping. By default, <a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> address mapping is
applied to envelope recipient addresses, and to header recipient
addresses. 

 Specify one or more of: envelope_recipient, header_recipient


 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="recipient_canonical_maps">recipient_canonical_maps</a>
(default: empty)</DT><DD>


Optional address mapping lookup tables for envelope and header
recipient addresses.
The table format and lookups are documented in <a href="canonical.5.html">canonical(5)</a>.



Note: $<a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> is processed before $<a href="postconf.5.html#canonical_maps">canonical_maps</a>.



Example:


<pre>
<a href="postconf.5.html#recipient_canonical_maps">recipient_canonical_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/recipient_canonical
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/recipient_canonical"
after you change the recipient_canonical file, to (re)build a
default-type indexed file. Execute "postmap
type:/etc/postfix/recipient_canonical" to specify an explicit
type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

</DD>

<DT><a name="recipient_delimiter">recipient_delimiter</a>
(default: empty)</DT><DD>

 The set of characters that can separate an email address
localpart, user name, or a .forward file name from its extension.
For example, with "<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = +", the software tries
user+foo@example.com before trying user@example.com, user+foo before
trying user, and .forward+foo before trying .forward. 

 More formally, an email address localpart or user name is
separated from its extension by the first character that matches
the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> set. The delimiter character and extension
may then be used to generate an extended .forward file name. This
implementation recognizes one delimiter character and one extension
per email address localpart or email address. With Postfix 2.10 and
earlier, the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> specifies a single character. 

 See <a href="canonical.5.html">canonical(5)</a>, <a href="local.8.html">local(8)</a>, <a href="relocated.5.html">relocated(5)</a> and <a href="virtual.5.html">virtual(5)</a> for the
effects of <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> on lookups in aliases, canonical,
virtual, and relocated maps, and see the <a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a>
parameter for propagating an extension from one email address to
another. 

 When used in <a href="postconf.5.html#command_execution_directory">command_execution_directory</a>, <a href="postconf.5.html#forward_path">forward_path</a>, or
<a href="postconf.5.html#luser_relay">luser_relay</a>, ${<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>} is replaced with the actual
recipient delimiter that was found in the recipient email address
(Postfix 2.11 and later), or it is replaced with the <a href="postconf.5.html">main.cf</a>
<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> parameter value (Postfix 2.10 and earlier).


 The <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> is not applied to the mailer-daemon
address, the postmaster address, or the double-bounce address. With
the default "<a href="postconf.5.html#owner_request_special">owner_request_special</a> = yes" setting, the <a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>
is also not applied to addresses with the special "owner-" prefix
or the special "-request" suffix. 


Examples:


<pre>
# Handle Postfix-style extensions.
<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = +
</pre>

<pre>
# Handle both Postfix and qmail extensions (Postfix 2.11 and later).
<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a> = +-
</pre>

<pre>
# Use .forward for mail without address extension, and for mail with
# an unrecognized address extension.
<a href="postconf.5.html#forward_path">forward_path</a> = $home/.forward${<a href="postconf.5.html#recipient_delimiter">recipient_delimiter</a>}${extension},
 $home/.forward
</pre>

</DD>

<DT><a name="reject_code">reject_code</a>
(default: 554)</DT><DD>


The numerical Postfix SMTP server response code when a remote SMTP
client request is rejected by the "reject" restriction.



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.


</DD>

<DT><a name="reject_tempfail_action">reject_tempfail_action</a>
(default: <a href="postconf.5.html#defer_if_permit">defer_if_permit</a>)</DT><DD>

 The Postfix SMTP server's action when a reject-type restriction
fails due to a temporary error condition. Specify "defer" to defer
the remote SMTP client request immediately. With the default
"<a href="postconf.5.html#defer_if_permit">defer_if_permit</a>" action, the Postfix SMTP server continues to look
for opportunities to reject mail, and defers the client request
only if it would otherwise be accepted. 

 For finer control, see: <a href="postconf.5.html#unverified_recipient_tempfail_action">unverified_recipient_tempfail_action</a>,
<a href="postconf.5.html#unverified_sender_tempfail_action">unverified_sender_tempfail_action</a>, <a href="postconf.5.html#unknown_address_tempfail_action">unknown_address_tempfail_action</a>,
and <a href="postconf.5.html#unknown_helo_hostname_tempfail_action">unknown_helo_hostname_tempfail_action</a>. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="relay_clientcerts">relay_clientcerts</a>
(default: empty)</DT><DD>

 List of tables with remote SMTP client-certificate fingerprints or
public key fingerprints (Postfix 2.9 and later) for which the Postfix
SMTP server will allow access with the <a href="postconf.5.html#permit_tls_clientcerts">permit_tls_clientcerts</a>
feature. The fingerprint digest algorithm is configurable via the
<a href="postconf.5.html#smtpd_tls_fingerprint_digest">smtpd_tls_fingerprint_digest</a> parameter (hard-coded as md5 prior to
Postfix version 2.5). 

 The default algorithm is sha256 with Postfix ≥ 3.6
and the <a href="postconf.5.html#compatibility_level">compatibility_level</a> set to 3.6 or higher. With Postfix
≤ 3.5, the default algorithm is md5. The best-practice
algorithm is now sha256. Recent advances in hash function
cryptanalysis have led to md5 and sha1 being deprecated in favor of
sha256. However, as long as there are no known "second pre-image"
attacks against the older algorithms, their use in this context, though
not recommended, is still likely safe. 

 Postfix lookup tables are in the form of (key, value) pairs.
Since we only need the key, the value can be chosen freely, e.g.
the name of the user or host:
D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80 lutzpc.at.home 

 Example: 

<pre>
<a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/relay_clientcerts
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

For more fine-grained control, use <a href="postconf.5.html#check_ccert_access">check_ccert_access</a> to select
an appropriate <a href="access.5.html">access(5)</a> policy for each client.
See <a href="RESTRICTION_CLASS_README.html">RESTRICTION_CLASS_README</a>.

 Execute the command "postmap /etc/postfix/relay_clientcerts"
after you change the <a href="postconf.5.html#relay_clientcerts">relay_clientcerts</a> file, to (re)build a default-type
indexed file. Execute "postmap type:/etc/postfix/relay_clientcerts"
to specify an explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

This feature is available with Postfix version 2.2.

</DD>

<DT><a name="relay_destination_concurrency_limit">relay_destination_concurrency_limit</a>
(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</DT><DD>

 The maximal number of parallel deliveries to the same destination
via the relay message delivery transport. This limit is enforced
by the queue manager. The message delivery transport name is the
first field in the entry in the <a href="master.5.html">master.cf</a> file. 

 This feature is available in Postfix 2.0 and later. 

</DD>

<DT><a name="relay_destination_recipient_limit">relay_destination_recipient_limit</a>
(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</DT><DD>

 The maximal number of recipients per message for the relay
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file. 

 Setting this parameter to a value of 1 changes the meaning of
<a href="postconf.5.html#relay_destination_concurrency_limit">relay_destination_concurrency_limit</a> from concurrency per domain
into concurrency per recipient. 

 This feature is available in Postfix 2.0 and later. 

</DD>

<DT><a name="relay_domains">relay_domains</a>
(default: Postfix ≥ 3.0: empty, Postfix < 3.0: $<a href="postconf.5.html#mydestination">mydestination</a>)</DT><DD>

 What destination domains (and subdomains thereof) this system
will relay mail to. For details about how
the <a href="postconf.5.html#relay_domains">relay_domains</a> value is used, see the description of the
<a href="postconf.5.html#permit_auth_destination">permit_auth_destination</a> and <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a> SMTP recipient
restrictions. 

 Domains that match $<a href="postconf.5.html#relay_domains">relay_domains</a> are delivered with the
$<a href="postconf.5.html#relay_transport">relay_transport</a> mail delivery transport. The SMTP server validates
recipient addresses with $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> and rejects non-existent
recipients. See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the
<a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a> file. 

 Note: Postfix will not automatically forward mail for domains
that list this system as their primary or backup MX host. See the
<a href="postconf.5.html#permit_mx_backup">permit_mx_backup</a> restriction in the <a href="postconf.5.html">postconf(5)</a> manual page. 

 Specify a list of host or domain names, "/file/name" patterns
or "<a href="DATABASE_README.html">type:table</a>" lookup tables, separated by commas and/or whitespace.
Continue long lines by starting the next line with whitespace. A
"/file/name" pattern is replaced by its contents; a "<a href="DATABASE_README.html">type:table</a>"
lookup table is matched when a (parent) domain appears as lookup
key. Specify "!pattern" to exclude a domain from the list. The form
"!/file/name" is supported only in Postfix version 2.4 and later.


 Pattern matching of domain names is controlled by the presence
or absence of "<a href="postconf.5.html#relay_domains">relay_domains</a>" in the <a href="postconf.5.html#parent_domain_matches_subdomains">parent_domain_matches_subdomains</a>
parameter value. 

</DD>

<DT><a name="relay_domains_reject_code">relay_domains_reject_code</a>
(default: 554)</DT><DD>


The numerical Postfix SMTP server response code when a client
request is rejected by the <a href="postconf.5.html#reject_unauth_destination">reject_unauth_destination</a> recipient
restriction.



Do not change this unless you have a complete understanding of <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>.


</DD>

<DT><a name="relay_recipient_maps">relay_recipient_maps</a>
(default: empty)</DT><DD>

 Optional lookup tables with all valid addresses in the domains
that match $<a href="postconf.5.html#relay_domains">relay_domains</a>. Specify @domain as a wild-card for
domains that have no valid recipient list, and become a source of
backscatter mail: Postfix accepts spam for non-existent recipients
and then floods innocent people with undeliverable mail. Technically,
tables
listed with $<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> are used as lists: Postfix needs
to know only if a lookup string is found or not, but it does not
use the result from the table lookup. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.



If this parameter is non-empty, then the Postfix SMTP server will reject
mail to unknown relay users. This feature is off by default.



See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>
file.



Example:


<pre>
<a href="postconf.5.html#relay_recipient_maps">relay_recipient_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/relay_recipients
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/relay_recipients"
after you change the relay_recipients file, to (re)build a default-type
indexed file. Execute "postmap type:/etc/postfix/relay_recipients"
to specify an explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 


This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="relay_transport">relay_transport</a>
(default: relay)</DT><DD>


The default mail delivery transport and next-hop destination for
the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domain</a> address class: recipient domains that match
$<a href="postconf.5.html#relay_domains">relay_domains</a>. 

 For recipient domains in the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domain</a> address class: 

<ul>

<li> In order of decreasing precedence, the message delivery
transport is taken from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2) $<a href="postconf.5.html#relay_transport">relay_transport</a>.


<li> In order of decreasing precedence, the nexthop destination
is taken from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2) $<a href="postconf.5.html#relay_transport">relay_transport</a>, 3)
$<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> or $<a href="postconf.5.html#relayhost">relayhost</a> or the recipient
domain. 

</ul>


Specify a string of the form transport:nexthop, where transport
is the name of a mail delivery transport defined in <a href="master.5.html">master.cf</a>.
The :nexthop destination is optional; its syntax is documented
in the manual page of the corresponding delivery agent.



See also the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domains</a> address class in the <a href="ADDRESS_CLASS_README.html">ADDRESS_CLASS_README</a>
file.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="relayhost">relayhost</a>
(default: empty)</DT><DD>


The next-hop destination(s) for non-local mail; takes precedence
over non-<a href="ADDRESS_CLASS_README.html#local_domain_class">local domains</a> in recipient addresses. This information
will not be used when the sender matches $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>.


 In order of decreasing precedence: 

<ul>

<li> For recipient domains in the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domain</a> address class
(domains matching $<a href="postconf.5.html#relay_domains">relay_domains</a>), the nexthop destination is taken
from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2) $<a href="postconf.5.html#relay_transport">relay_transport</a>, 3)
$<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> or $<a href="postconf.5.html#relayhost">relayhost</a> or the recipient
domain. 

<li> For recipient domains in the <a href="ADDRESS_CLASS_README.html#default_domain_class">default domain</a> address class
(domains that do not match $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>,
$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>,
or $<a href="postconf.5.html#relay_domains">relay_domains</a>), the nexthop destination is taken from 1)
$<a href="postconf.5.html#transport_maps">transport_maps</a>, 2) $<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> or
$<a href="postconf.5.html#default_transport">default_transport</a>, 3) $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> or $<a href="postconf.5.html#relayhost">relayhost</a>
or the recipient domain. 

</ul>


On an intranet, specify the organizational domain name. If your
internal DNS uses no MX records, specify the name of the intranet
gateway host instead.



In the case of SMTP delivery, specify one or more destinations in
the form of a domain name, hostname, hostname:service, [hostname]:service,
[hostaddress] or [hostaddress]:service, separated by comma or whitespace.
The form [hostname] turns off MX or SRV lookups. Multiple destinations
are supported in Postfix 3.5 and later. Each destination is tried
in the specified order.


 If an SMTP destination is a load balancer, and there are no
alternative destinations, specify the load balancer multiple times.
Without the duplicate info, the Postfix SMTP client would not
reconnect immediately to the same load balancer after a remote SMTP
server failure. 


If you're connected via UUCP, see the <a href="UUCP_README.html">UUCP_README</a> file for useful
information.



Examples:


<pre>
<a href="postconf.5.html#relayhost">relayhost</a> = $<a href="postconf.5.html#mydomain">mydomain</a>
<a href="postconf.5.html#relayhost">relayhost</a> = [gateway.example.com]
<a href="postconf.5.html#relayhost">relayhost</a> = mail1.example:587, mail2.example:587
<a href="postconf.5.html#relayhost">relayhost</a> = [an.ip.add.ress]
</pre>

</DD>

<DT><a name="relocated_maps">relocated_maps</a>
(default: empty)</DT><DD>


Optional lookup tables with new contact information for users or
domains that no longer exist. The table format and lookups are
documented in <a href="relocated.5.html">relocated(5)</a>.



Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.



Examples:


<pre>
<a href="postconf.5.html#relocated_maps">relocated_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/relocated
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/relocated" after you
change the relocated file, to (re)build a default-type indexed file.
Execute "postmap type:/etc/postfix/relocated" to specify an
explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

</DD>

<DT><a name="relocated_prefix_enable">relocated_prefix_enable</a>
(default: yes)</DT><DD>

 Prepend the prefix "5.1.6 User has moved to " to all
<a href="postconf.5.html#relocated_maps">relocated_maps</a> lookup results. With "<a href="postconf.5.html#relocated_prefix_enable">relocated_prefix_enable</a> =
no", all lookup results must contain a valid <a href="https://tools.ietf.org/html/rfc3463">RFC 3463</a> compliant
enhanced status code and text (format: "[45].number.number text...").


Example:


<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#relocated_maps">relocated_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/relocated
 <a href="postconf.5.html#relocated_prefix_enable">relocated_prefix_enable</a> = no
 
/etc/postfix/relocated:
 user@example.com 5.2.1 User account is disabled
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/relocated" after you
change the relocated file, to (re)build a default-type indexed file.
Execute "postmap type:/etc/postfix/relocated" to specify an
explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

 This feature is available in Postfix 3.11 and later. 

</DD>

<DT><a name="remote_header_rewrite_domain">remote_header_rewrite_domain</a>
(default: empty)</DT><DD>

 Rewrite or add message headers in mail from remote clients if
the <a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter value is non-empty,
updating incomplete addresses with the domain specified in the
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> parameter, and adding missing headers.


 The
<a href="postconf.5.html#local_header_rewrite_clients">local_header_rewrite_clients</a> parameter controls what clients Postfix
considers local. 

 Examples: 

 The safe setting: append "domain.invalid" to incomplete header
addresses from remote SMTP clients, so that those addresses cannot
be confused with local addresses. 

<blockquote>
<pre>
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> = domain.invalid
</pre>
</blockquote>

 The default, purist, setting: don't rewrite headers from remote
clients at all. 

<blockquote>
<pre>
<a href="postconf.5.html#remote_header_rewrite_domain">remote_header_rewrite_domain</a> =
</pre>
</blockquote>

</DD>

<DT><a name="require_home_directory">require_home_directory</a>
(default: no)</DT><DD>


Require that a <a href="local.8.html">local(8)</a> recipient's home directory exists
before mail delivery is attempted. By default this test is disabled.
It can be useful for environments that import home directories to
the mail server (IMPORTING HOME DIRECTORIES IS NOT RECOMMENDED).


</DD>

<DT><a name="requiretls_enable">requiretls_enable</a>
(default: yes)</DT><DD>

 Enable support for the ESMTP verb "REQUIRETLS" in the "MAIL
FROM" command. As defined in <a href="https://tools.ietf.org/html/rfc8689">RFC 8689</a>, when a message specifies
REQUIRETLS: 

<ul>

<li> deliveries with SMTP or LMTP must use a TLS connection, 

<li> to a securely looked up MX server (e.g., DNSSEC or MTA-STS),


<li> with a matched server certificate (Postfix SMTP or LMTP
client TLS security levels "secure", "verify", "fingerprint",
dane-only, or opportunistic "dane"), 

<li> and the server must announce "REQUIRETLS" support after
the STARTTLS handshake. 

</ul>

 When delivering a message that specifies REQUIRETLS, the Postfix
SMTP client will try one or more servers, limited by the
<a href="postconf.5.html#smtp_mx_address_limit">smtp_mx_address_limit</a> and <a href="postconf.5.html#smtp_mx_session_limit">smtp_mx_session_limit</a> parameters, until
it finds an MX server that satisfies the above requirements. If
such a server is not found, the Postfix SMTP or LMTP client returns
the message as undeliverable. 

 Notes: 

<ul>

<li> With the Postfix SMTP or LMTP clients, REQUIRETLS enforcement
is controlled with <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> or <a href="postconf.5.html#lmtp_requiretls_policy">lmtp_requiretls_policy</a>. It
is initially not enforced for deliveries to local servers, including
LMTP message stores and local content filters. 

<li> The ESMTP REQUIRETLS option overrides the "TLS-Required:
no" message header. 

</ul>

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="requiretls_esmtp_header">requiretls_esmtp_header</a>
(default: yes)</DT><DD>

 Record the ESMTP REQUIRETLS request in a "Require-TLS-ESMTP:
yes" message header. This is needed to propagate the REQUIRETLS
request through an external content filter that is configured with
<a href="postconf.5.html#smtpd_proxy_filter">smtpd_proxy_filter</a>, with <a href="postconf.5.html#content_filter">content_filter</a>, or with a FILTER action in
an SMTPD <a href="access.5.html">access(5)</a> table, <a href="header_checks.5.html">header_checks(5)</a> or <a href="header_checks.5.html">body_checks(5)</a>. The
header is not needed with Milter-based content filters. 

 This header will be visible to remote and local recipients. It
can safely be disabled if a configuration does not use any of the
above content filters that need the header. 

 This feature is available in Postfix 3.11 and later. 

</DD>

<DT><a name="requiretls_redact_dsn">requiretls_redact_dsn</a>
(default: yes)</DT><DD>

 When sending a delivery status notification for an original
message received with the REQUIRETLS option, do not send the original
message body (as if that message was received with "RET=HDRS") and
do not enforce REQUIRETLS (as if that message was received without
REQUIRETLS). For a detailed discussion see <a href="https://tools.ietf.org/html/rfc8689">RFC 8689</a> section 5. 

 Note: the 'reverse' path for sending a delivery status notification
may differ from the 'forward' path for receiving the original message.
Not every hop in the reverse path may support REQUIRETLS, even
though every hop in the forward path supported it. The setting
"<a href="postconf.5.html#requiretls_redact_dsn">requiretls_redact_dsn</a> = no" may therefore result in the loss of a
delivery status notification. 

</DD>

<DT><a name="reset_owner_alias">reset_owner_alias</a>
(default: no)</DT><DD>

 Reset the <a href="local.8.html">local(8)</a> delivery agent's idea of the owner-alias
attribute, when delivering mail to a child alias that does not have
its own owner alias. 

 This feature is available in Postfix 2.8 and later. With older
Postfix releases, the behavior is as if this parameter is set to
"yes". 

 As documented in <a href="aliases.5.html">aliases(5)</a>, when an alias name has a
companion alias named owner-name, this will replace the
envelope sender address, so that delivery errors will be
reported to the owner alias instead of the sender. This configuration
is recommended for mailing lists. 

 A less known property of the owner alias is that it also forces
the <a href="local.8.html">local(8)</a> delivery agent to write local and remote addresses
from alias expansion to a new queue file, instead of attempting to
deliver mail to local addresses as soon as they come out of alias
expansion. 

 Writing local addresses from alias expansion to a new queue
file allows for robust handling of temporary delivery errors: errors
with one local member have no effect on deliveries to other members
of the list. On the other hand, delivery to local addresses as
soon as they come out of alias expansion is fragile: a temporary
error with one local address from alias expansion will cause the
entire alias to be expanded repeatedly until the error goes away,
or until the message expires in the queue. In that case, a problem
with one list member results in multiple message deliveries to other
list members. 

 The default behavior of Postfix 2.8 and later is to keep the
owner-alias attribute of the parent alias, when delivering mail to
a child alias that does not have its own owner alias. Then, local
addresses from that child alias will be written to a new queue file,
and a temporary error with one local address will not affect delivery
to other mailing list members. 

 Unfortunately, older Postfix releases reset the owner-alias
attribute when delivering mail to a child alias that does not have
its own owner alias. To be precise, this resets only the decision
to create a new queue file, not the decision to override the envelope
sender address. The <a href="local.8.html">local(8)</a> delivery agent then attempts to
deliver local addresses as soon as they come out of child alias
expansion. If delivery to any address from child alias expansion
fails with a temporary error condition, the entire mailing list may
be expanded repeatedly until the mail expires in the queue, resulting
in multiple deliveries of the same message to mailing list members.


</DD>

<DT><a name="resolve_dequoted_address">resolve_dequoted_address</a>
(default: yes)</DT><DD>

 Resolve a recipient address safely instead of correctly, by
looking inside quotes. 

 By default, the Postfix address resolver does not quote the
address localpart as per <a href="https://tools.ietf.org/html/rfc822">RFC 822</a>, so that additional @ or % or !
operators remain visible. This behavior is safe but it is also
technically incorrect. 

 If you specify "<a href="postconf.5.html#resolve_dequoted_address">resolve_dequoted_address</a> = no", then
the Postfix
resolver will not know about additional @ etc. operators in the
address localpart. This opens opportunities for obscure mail relay
attacks with user@domain@domain addresses when Postfix provides
backup MX service for Sendmail systems. 

</DD>

<DT><a name="resolve_null_domain">resolve_null_domain</a>
(default: no)</DT><DD>

 Resolve an address that ends in the "@" null domain as if the
local hostname were specified, instead of rejecting the address as
invalid. 

 This feature is available in Postfix 2.1 and later.
Earlier versions always resolve the null domain as the local
hostname. 

 The Postfix SMTP server uses this feature to reject mail from
or to addresses that end in the "@" null domain, and from addresses
that rewrite into a form that ends in the "@" null domain. 

</DD>

<DT><a name="resolve_numeric_domain">resolve_numeric_domain</a>
(default: no)</DT><DD>

 Resolve "user@ipaddress" as "user@[ipaddress]", instead of
rejecting the address as invalid. 

 This feature is available in Postfix 2.3 and later.

</DD>

<DT><a name="respectful_logging">respectful_logging</a>
(default: see 'postconf -d' output)</DT><DD>

 Avoid logging that implies white is better than black. Instead
use 'allowlist', 'denylist', and variations of those words. 

 This feature is available in Postfix 3.6 and later. 

</DD>

<DT><a name="rewrite_service_name">rewrite_service_name</a>
(default: rewrite)</DT><DD>


The name of the address rewriting service. This service rewrites
addresses to standard form and resolves them to a (delivery method,
next-hop host, recipient) triple.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="sample_directory">sample_directory</a>
(default: /etc/postfix)</DT><DD>


The name of the directory with example Postfix configuration files.
Starting with Postfix 2.1, these files have been replaced with the
<a href="postconf.5.html">postconf(5)</a> manual page.


</DD>

<DT><a name="send_cyrus_sasl_authzid">send_cyrus_sasl_authzid</a>
(default: no)</DT><DD>

 When authenticating to a remote SMTP or LMTP server with the
default setting "no", send no SASL authoriZation ID (authzid); send
only the SASL authentiCation ID (authcid) plus the authcid's password.


 The non-default setting "yes" enables the behavior of older
Postfix versions. These always send a SASL authzid that is equal
to the SASL authcid, but this causes interoperability problems
with some SMTP servers. 

 This feature is available in Postfix 2.4.4 and later. 

</DD>

<DT><a name="sender_based_routing">sender_based_routing</a>
(default: no)</DT><DD>


This parameter should not be used. It was replaced by <a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
in Postfix version 2.3.


</DD>

<DT><a name="sender_bcc_maps">sender_bcc_maps</a>
(default: empty)</DT><DD>

 Optional BCC (blind carbon-copy) address lookup tables, indexed
by envelope sender address. The BCC address (multiple results are not
supported) is added when mail enters from outside of Postfix. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.



The table search order is as follows:


<ul>

<li> Look up the "user+extension@domain.tld" address including the
optional address extension.

<li> Look up the "user@domain.tld" address without the optional
address extension.

<li> Look up the "user+extension" address local part when the
sender domain equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>
or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "user" address local part when the sender domain
equals $<a href="postconf.5.html#myorigin">myorigin</a>, $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> or $<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>.

<li> Look up the "@domain.tld" part.

</ul>


Note: with Postfix 2.3 and later the BCC address is added as if it
was specified with NOTIFY=NONE. The sender will not be notified
when the BCC address is undeliverable, as long as all down-stream
software implements <a href="https://tools.ietf.org/html/rfc3461">RFC 3461</a>.



Note: with Postfix 2.2 and earlier the sender will be notified
when the BCC address is undeliverable.


 Note: automatic BCC recipients are produced only for new mail.
To avoid mailer loops, automatic BCC recipients are not generated
after Postfix forwards mail internally, or after Postfix generates
mail itself. 

 Note: automatic BCC recipients are subject to address
canonicalization (add missing domain), <a href="postconf.5.html#canonical_maps">canonical_maps</a>, <a href="postconf.5.html#masquerade_domains">masquerade_domains</a>,
and <a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a>. 


Example:


<pre>
<a href="postconf.5.html#sender_bcc_maps">sender_bcc_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/sender_bcc
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/sender_bcc" after you
change the sender_bcc file, to (re)build a default-type indexed file.
Execute "postmap type:/etc/postfix/sender_bcc" to specify an
explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="sender_canonical_classes">sender_canonical_classes</a>
(default: envelope_sender, header_sender)</DT><DD>

 What addresses are subject to <a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> address
mapping. By default, <a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> address mapping is
applied to envelope sender addresses, and to header sender addresses.


 Specify one or more of: envelope_sender, header_sender 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="sender_canonical_maps">sender_canonical_maps</a>
(default: empty)</DT><DD>


Optional address mapping lookup tables for envelope and header
sender addresses.
The table format and lookups are documented in <a href="canonical.5.html">canonical(5)</a>.



Example: you want to rewrite the SENDER address "user@ugly.example"
to "user@pretty.example", while still being able to send mail to
the RECIPIENT address "user@ugly.example".



Note: $<a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> is processed before $<a href="postconf.5.html#canonical_maps">canonical_maps</a>.



Example:


<pre>
<a href="postconf.5.html#sender_canonical_maps">sender_canonical_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/sender_canonical
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/sender_canonical"
after you change the sender_canonical file, to (re)build a default-type
indexed file. Execute "postmap type:/etc/postfix/sender_canonical"
to specify an explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

</DD>

<DT><a name="sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a>
(default: empty)</DT><DD>

 A sender-dependent override for the global <a href="postconf.5.html#default_transport">default_transport</a>
parameter setting. The tables are searched by the envelope sender
address and @domain. A lookup result of DUNNO terminates the search
without overriding the global <a href="postconf.5.html#default_transport">default_transport</a> parameter setting.
This information is overruled with the <a href="transport.5.html">transport(5)</a> table. 

 This setting affects only the <a href="ADDRESS_CLASS_README.html#default_domain_class">default domain</a> address class
(recipient domains that do not match $<a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>,
$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>,
or $<a href="postconf.5.html#relay_domains">relay_domains</a>): 

<ul>

<li> In order of decreasing precedence, the delivery transport
is taken from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2)
$<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> or $<a href="postconf.5.html#default_transport">default_transport</a>.


<li> In order of decreasing precedence, the nexthop destination
is taken from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2)
$<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> or $<a href="postconf.5.html#default_transport">default_transport</a>, 3)
$<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> or $<a href="postconf.5.html#relayhost">relayhost</a> or the recipient
domain. 

</ul>

 Note: this overrides <a href="postconf.5.html#default_transport">default_transport</a>, not <a href="postconf.5.html#transport_maps">transport_maps</a>, and
therefore the expected syntax is that of <a href="postconf.5.html#default_transport">default_transport</a>, not the
syntax of <a href="postconf.5.html#transport_maps">transport_maps</a>. Specifically, this does not support the
<a href="postconf.5.html#transport_maps">transport_maps</a> syntax for null transport, null nexthop, or null
email addresses. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


 For safety reasons, this feature does not allow $number
substitutions in regular expression maps. 

 This feature is available in Postfix 2.7 and later. 

</DD>

<DT><a name="sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a>
(default: empty)</DT><DD>

 A sender-dependent override for the global <a href="postconf.5.html#relayhost">relayhost</a> parameter
setting. The tables are searched by the envelope sender address and
@domain. A lookup result of DUNNO terminates the search without
overriding the global <a href="postconf.5.html#relayhost">relayhost</a> parameter setting (Postfix 2.6 and
later). 

 In order of decreasing precedence: 

<ul>

<li> For recipient domains in the <a href="ADDRESS_CLASS_README.html#relay_domain_class">relay domain</a> address class
(domains matching $<a href="postconf.5.html#relay_domains">relay_domains</a>), the nexthop destination is taken
from 1) $<a href="postconf.5.html#transport_maps">transport_maps</a>, 2) $<a href="postconf.5.html#relay_transport">relay_transport</a>, 3)
$<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> or $<a href="postconf.5.html#relayhost">relayhost</a> or the recipient
domain. 

<li> For recipient domains in the <a href="ADDRESS_CLASS_README.html#default_domain_class">default domain</a> address class
(domains that do not match <a href="postconf.5.html#mydestination">mydestination</a>, $<a href="postconf.5.html#inet_interfaces">inet_interfaces</a>,
$<a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a>, $<a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a>, $<a href="postconf.5.html#virtual_mailbox_domains">virtual_mailbox_domains</a>,
$<a href="postconf.5.html#relay_domains">relay_domains</a>), the nexthop destination is taken from 1)
$<a href="postconf.5.html#transport_maps">transport_maps</a>, 2) $<a href="postconf.5.html#sender_dependent_default_transport_maps">sender_dependent_default_transport_maps</a> or
$<a href="postconf.5.html#default_transport">default_transport</a>, 3) $<a href="postconf.5.html#sender_dependent_relayhost_maps">sender_dependent_relayhost_maps</a> or $<a href="postconf.5.html#relayhost">relayhost</a>
or the recipient domain. 

</ul>


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


 For safety reasons, this feature does not allow $number
substitutions in regular expression maps. 


This feature is available in Postfix 2.3 and later.


</DD>

<DT><a name="sendmail_fix_line_endings">sendmail_fix_line_endings</a>
(default: always)</DT><DD>

 Controls how the Postfix sendmail command converts email message
line endings from <CR><LF> into UNIX format (<LF>).


<dl>

<dt> always </dt> <dd> Always convert message lines ending
in <CR><LF>. This setting is the default with Postfix
2.9 and later. </dd>

<dt> strict </dt> <dd> Convert message lines ending in
<CR><LF> only if the first input line ends in
<CR><LF>. This setting is backwards-compatible with
Postfix 2.8 and earlier. </dd>

<dt> never </dt> <dd> Never convert message lines ending in
<CR><LF>. This setting exists for completeness only.
</dd>

</dl>

 This feature is available in Postfix 2.9 and later. 

</DD>

<DT><a name="sendmail_path">sendmail_path</a>
(default: see "postconf -d" output)</DT><DD>


A Sendmail compatibility feature that specifies the location of
the Postfix <a href="sendmail.1.html">sendmail(1)</a> command. This command can be used to
submit mail into the Postfix queue.


</DD>

<DT><a name="service_name">service_name</a>
(read-only)</DT><DD>

 The <a href="master.5.html">master.cf</a> service name of a Postfix daemon process. This
can be used to distinguish the logging from different services that
use the same program name. 

 Example <a href="master.5.html">master.cf</a> entries: 

<pre>
# Distinguish inbound MTA logging from submission and submissions logging.
smtp inet n - n - - smtpd
submission inet n - n - - smtpd
 -o <a href="postconf.5.html#syslog_name">syslog_name</a>=postfix/$<a href="postconf.5.html#service_name">service_name</a>
submissions inet n - n - - smtpd
 -o <a href="postconf.5.html#syslog_name">syslog_name</a>=postfix/$<a href="postconf.5.html#service_name">service_name</a>
</pre>

<pre>
# Distinguish outbound MTA logging from inbound relay logging.
smtp unix - - n - - smtp
relay unix - - n - - smtp
 -o <a href="postconf.5.html#syslog_name">syslog_name</a>=postfix/$<a href="postconf.5.html#service_name">service_name</a>
</pre>

 This feature is available in Postfix 3.3 and later. 

</DD>

<DT><a name="service_throttle_time">service_throttle_time</a>
(default: 60s)</DT><DD>


How long the Postfix <a href="master.8.html">master(8)</a> waits before forking a server that
appears to be malfunctioning.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="setgid_group">setgid_group</a>
(default: postdrop)</DT><DD>


The group ownership of set-gid Postfix commands and of group-writable
Postfix directories. When this parameter value is changed you need
to re-run "postfix set-permissions" (with Postfix version 2.0 and
earlier: "/etc/postfix/post-install set-permissions".


</DD>

<DT><a name="shlib_directory">shlib_directory</a>
(default: see 'postconf -d' output)</DT><DD>

 The location of Postfix dynamically-linked libraries
(libpostfix-*.so), and the default location of Postfix database
plugins (postfix-*.so) that have a relative pathname in the
dynamicmaps.cf file. The <a href="postconf.5.html#shlib_directory">shlib_directory</a> parameter defaults to
"no" when Postfix dynamically-linked libraries and database plugins
are disabled at compile time, otherwise it typically defaults to
/usr/lib/postfix or /usr/local/lib/postfix. 

 Notes: 

<ul>

<li> The directory specified with <a href="postconf.5.html#shlib_directory">shlib_directory</a> should contain
only Postfix-related files. Postfix dynamically-linked libraries
and database plugins should not be installed in a "public" system
directory such as /usr/lib or /usr/local/lib. Linking Postfix
dynamically-linked library files or database plugins into non-Postfix
programs is not supported. Postfix dynamically-linked libraries
and database plugins implement a Postfix-internal API that changes
without maintaining compatibility. 

<li> You can change the <a href="postconf.5.html#shlib_directory">shlib_directory</a> value after Postfix is
built. However, you may have to run ldconfig or equivalent to prevent
Postfix programs from failing because the libpostfix-*.so files are
not found. No ldconfig command is needed if you keep the libpostfix-*.so
files in the compiled-in default $<a href="postconf.5.html#shlib_directory">shlib_directory</a> location. 

</ul>

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="show_user_unknown_table_name">show_user_unknown_table_name</a>
(default: yes)</DT><DD>


Display the name of the recipient table in the "User unknown"
responses. The extra detail makes troubleshooting easier but also
reveals information that is nobody else's business.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="showq_service_name">showq_service_name</a>
(default: showq)</DT><DD>


The name of the <a href="showq.8.html">showq(8)</a> service. This service produces mail queue
status reports.



This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="smtp_address_preference">smtp_address_preference</a>
(default: any)</DT><DD>

 The address type ("ipv6", "ipv4" or "any") that the Postfix
SMTP client will try first, when a destination has IPv6 and IPv4
addresses with equal MX preference. This feature has no effect
unless the <a href="postconf.5.html#inet_protocols">inet_protocols</a> setting enables both IPv4 and IPv6. 

 Postfix SMTP client address preference has evolved. With Postfix
2.8 the default is "ipv6"; earlier implementations are hard-coded
to prefer IPv6 over IPv4. 

 Notes for mail delivery between sites that have both IPv4 and
IPv6 connectivity: 

<ul>

<li> The setting "<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> = ipv6" is unsafe.
All deliveries will suffer delays during an IPv6 outage, even
while the destination is still reachable over IPv4. Mail may be
stuck in the queue with Postfix versions < 3.3 that do not
implement "<a href="postconf.5.html#smtp_balance_inet_protocols">smtp_balance_inet_protocols</a>". For similar reasons, the
setting "<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> = ipv4" is also unsafe. 

<li> The setting "<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> = any" is safe. With
this, and "<a href="postconf.5.html#smtp_balance_inet_protocols">smtp_balance_inet_protocols</a> = yes" (the default), only
half of deliveries will suffer delays if there is an outage
that affects IPv6 or IPv4, as long as it does not affect both. 

<li> The setting "<a href="postconf.5.html#smtp_address_preference">smtp_address_preference</a> = ipv4" is not a
solution for remote servers that flag email received over IPv6 as
more 'spammy' (the client IPv6 address has a bad or missing PTR or
AAAA record, bad network neighbors, etc.). Instead, configure Postfix
to receive mail over both IPv4 and IPv6, and to deliver mail over
only IPv4. 

<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#inet_protocols">inet_protocols</a> = all
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>
 smtp ...other fields... smtp -o <a href="postconf.5.html#inet_protocols">inet_protocols</a>=ipv4
</pre>
</blockquote>

</ul>

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="smtp_address_verify_target">smtp_address_verify_target</a>
(default: rcpt)</DT><DD>

 In the context of email address verification, the SMTP protocol
stage that determines whether an email address is deliverable.
Specify one of "rcpt" or "data". The latter is needed with remote
SMTP servers that reject recipients after the DATA command. Use
<a href="postconf.5.html#transport_maps">transport_maps</a> to apply this feature selectively: 

<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#transport_maps">transport_maps</a> = <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/transport
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/transport:
 smtp-domain-that-verifies-after-data smtp-data-target:
 lmtp-domain-that-verifies-after-data lmtp-data-target:
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
 smtp-data-target unix - - n - - smtp
 -o <a href="postconf.5.html#smtp_address_verify_target">smtp_address_verify_target</a>=data
 lmtp-data-target unix - - n - - lmtp
 -o <a href="postconf.5.html#lmtp_address_verify_target">lmtp_address_verify_target</a>=data
</pre>
</blockquote>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Unselective use of the "data" target does no harm, but will
result in unnecessary "lost connection after DATA" events at remote
SMTP/LMTP servers. 

 Execute the command "postmap /etc/postfix/transport" after you
change the transport file, to (re)build a default-type indexed file.
Execute "postmap type:/etc/postfix/transport" to specify an
explicit type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="smtp_always_send_ehlo">smtp_always_send_ehlo</a>
(default: yes)</DT><DD>


Always send EHLO at the start of an SMTP session.



With "<a href="postconf.5.html#smtp_always_send_ehlo">smtp_always_send_ehlo</a> = no", the Postfix SMTP client sends
EHLO only when
the word "ESMTP" appears in the server greeting banner (example:
220 spike.porcupine.org ESMTP Postfix).


</DD>

<DT><a name="smtp_balance_inet_protocols">smtp_balance_inet_protocols</a>
(default: yes)</DT><DD>

 When a remote destination resolves to a combination of IPv4 and
IPv6 addresses, ensure that the Postfix SMTP client can try both
address types before it runs into the <a href="postconf.5.html#smtp_mx_address_limit">smtp_mx_address_limit</a>. 

 This avoids an interoperability problem when a destination resolves
to primarily IPv6 addresses, the smtp_address_limit feature eliminates
most or all IPv4 addresses, and the destination is not reachable over
IPv6. 

 This feature is available in Postfix 3.3 and later. 

</DD>

<DT><a name="smtp_bind_address">smtp_bind_address</a>
(default: empty)</DT><DD>


An optional numerical network address that the Postfix SMTP client
should bind to when making an IPv4 connection.



This can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP clients, or
it can be specified in the <a href="master.5.html">master.cf</a> file for a specific client,
for example:


<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
 smtp ... smtp -o <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a>=11.22.33.44
</pre>
</blockquote>

 See <a href="postconf.5.html#smtp_bind_address_enforce">smtp_bind_address_enforce</a> for how Postfix should handle
errors (Postfix 3.7 and later). 

 Note 1: when <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies no more than one IPv4
address, and that address is a non-loopback address, it is
automatically used as the <a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a>. This supports virtual
IP hosting, but can be a problem on multi-homed firewalls. See the
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> documentation for more detail. 

 Note 2: address information may be enclosed inside <tt>[]</tt>,
but this form is not required here. 

</DD>

<DT><a name="smtp_bind_address6">smtp_bind_address6</a>
(default: empty)</DT><DD>


An optional numerical network address that the Postfix SMTP client
should bind to when making an IPv6 connection.


 This feature is available in Postfix 2.2 and later. 


This can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP clients, or
it can be specified in the <a href="master.5.html">master.cf</a> file for a specific client,
for example:


<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
 smtp ... smtp -o <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a>=1:2:3:4:5:6:7:8
</pre>
</blockquote>

 See <a href="postconf.5.html#smtp_bind_address_enforce">smtp_bind_address_enforce</a> for how Postfix should handle
errors (Postfix 3.7 and later). 

 Note 1: when <a href="postconf.5.html#inet_interfaces">inet_interfaces</a> specifies no more than one IPv6
address, and that address is a non-loopback address, it is
automatically used as the <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a>. This supports virtual
IP hosting, but can be a problem on multi-homed firewalls. See the
<a href="postconf.5.html#inet_interfaces">inet_interfaces</a> documentation for more detail. 

 Note 2: address information may be enclosed inside <tt>[]</tt>,
but this form is not recommended here. 

</DD>

<DT><a name="smtp_bind_address_enforce">smtp_bind_address_enforce</a>
(default: no)</DT><DD>

 Defer delivery when the Postfix SMTP client cannot apply the
<a href="postconf.5.html#smtp_bind_address">smtp_bind_address</a> or <a href="postconf.5.html#smtp_bind_address6">smtp_bind_address6</a> setting. By default, the
Postfix SMTP client will continue delivery after logging a warning.


 This feature is available in Postfix 3.7 and later. 

</DD>

<DT><a name="smtp_body_checks">smtp_body_checks</a>
(default: empty)</DT><DD>

 Restricted <a href="header_checks.5.html">body_checks(5)</a> tables for the Postfix SMTP client.
These tables are searched while mail is being delivered. Actions
that change the delivery time or destination are not available.


 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="smtp_cname_overrides_servername">smtp_cname_overrides_servername</a>
(default: version dependent)</DT><DD>

 When the remote SMTP servername is a DNS CNAME, replace the
servername with the result from CNAME expansion for the purpose of
logging, SASL password lookup, TLS
policy decisions, or TLS certificate verification. The value "no"
hardens Postfix <a href="postconf.5.html#smtp_tls_per_site">smtp_tls_per_site</a> hostname-based policies against
false hostname information in DNS CNAME records, and makes SASL
password file lookups more predictable. This is the default setting
as of Postfix 2.3. 

 This feature is available in Postfix 2.2.9 and later, deprecated
as of Postfix 3.11. 

</DD>

<DT><a name="smtp_connect_timeout">smtp_connect_timeout</a>
(default: 30s)</DT><DD>


The Postfix SMTP client time limit for completing a TCP connection, or
zero (use the operating system built-in time limit).



When no connection can be made within the deadline, the Postfix
SMTP client
tries the next address on the mail exchanger list. Specify 0 to
disable the time limit (i.e. use whatever timeout is implemented by
the operating system).


 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="smtp_connection_cache_destinations">smtp_connection_cache_destinations</a>
(default: empty)</DT><DD>

 Permanently enable SMTP connection caching for the specified
destinations. With SMTP connection caching, a connection is not
closed immediately after completion of a mail transaction. Instead,
the connection is kept open for up to $<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a>
seconds. This allows connections to be reused for other deliveries,
and can improve mail delivery performance. 

 Specify a comma or white space separated list of destinations
or pseudo-destinations: 

<ul>

<li> if mail is sent without a <a href="postconf.5.html#relayhost">relay host</a>: a domain name (the
right-hand side of an email address, without the [] around a numeric
IP address),

<li> if mail is sent via a <a href="postconf.5.html#relayhost">relay host</a>: a <a href="postconf.5.html#relayhost">relay host</a> name (without
[] or non-default TCP port), as specified in <a href="postconf.5.html">main.cf</a> or in the
transport map,

<li> if mail is sent via a UNIX-domain socket: a pathname (without
the unix: prefix),

<li> a /file/name with domain names and/or <a href="postconf.5.html#relayhost">relay host</a> names as
defined above,

<li> a "<a href="DATABASE_README.html">type:table</a>" with domain names and/or <a href="postconf.5.html#relayhost">relay host</a> names on
the left-hand side. The right-hand side result from "<a href="DATABASE_README.html">type:table</a>"
lookups is ignored.

</ul>

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_connection_cache_on_demand">smtp_connection_cache_on_demand</a>
(default: yes)</DT><DD>

 Temporarily enable SMTP connection caching while a destination
has a high volume of mail in the <a href="QSHAPE_README.html#active_queue">active queue</a>. With SMTP connection
caching, a connection is not closed immediately after completion
of a mail transaction. Instead, the connection is kept open for
up to $<a href="postconf.5.html#smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a> seconds. This allows
connections to be reused for other deliveries, and can improve mail
delivery performance. 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_connection_cache_time_limit">smtp_connection_cache_time_limit</a>
(default: 2s)</DT><DD>

 When SMTP connection caching is enabled, the amount of time that
an unused SMTP client socket is kept open before it is closed. Do
not specify larger values without permission from the remote sites.


 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_connection_reuse_count_limit">smtp_connection_reuse_count_limit</a>
(default: 0)</DT><DD>

 When SMTP connection caching is enabled, the number of times
that an SMTP session may be reused before it is closed, or zero (no
limit). With a reuse count limit of N, a connection is used up to
N+1 times. 

 NOTE: This feature is unsafe. When a high-volume destination
has multiple inbound MTAs, then the slowest inbound MTA will attract
the most connections to that destination. This limitation does not
exist with the <a href="postconf.5.html#smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a> feature. 

 This feature is available in Postfix 2.11. 

</DD>

<DT><a name="smtp_connection_reuse_time_limit">smtp_connection_reuse_time_limit</a>
(default: 300s)</DT><DD>

 The amount of time during which Postfix will use an SMTP
connection repeatedly. The timer starts when the connection is
initiated (i.e. it includes the connect, greeting and helo latency,
in addition to the latencies of subsequent mail delivery transactions).


 This feature addresses a performance stability problem with
remote SMTP servers. This problem is not specific to Postfix: it
can happen when any MTA sends large amounts of SMTP email to a site
that has multiple MX hosts. 

 The problem starts when one of a set of MX hosts becomes slower
than the rest. Even though SMTP clients connect to fast and slow
MX hosts with equal probability, the slow MX host ends up with more
simultaneous inbound connections than the faster MX hosts, because
the slow MX host needs more time to serve each client request. 

 The slow MX host becomes a connection attractor. If one MX
host becomes N times slower than the rest, it dominates mail delivery
latency unless there are more than N fast MX hosts to counter the
effect. And if the number of MX hosts is smaller than N, the mail
delivery latency becomes effectively that of the slowest MX host
divided by the total number of MX hosts. 

 The solution uses connection caching in a way that differs from
Postfix version 2.2. By limiting the amount of time during which a connection
can be used repeatedly (instead of limiting the number of deliveries
over that connection), Postfix not only restores fairness in the
distribution of simultaneous connections across a set of MX hosts,
it also favors deliveries over connections that perform well, which
is exactly what we want. 

 The default reuse time limit, 300s, is comparable to the various
smtp transaction timeouts which are fair estimates of maximum excess
latency for a slow delivery. Note that hosts may accept thousands
of messages over a single connection within the default connection
reuse time limit. This number is much larger than the default Postfix
version 2.2 limit of 10 messages per cached connection. It may prove necessary
to lower the limit to avoid interoperability issues with MTAs that
exhibit bugs when many messages are delivered via a single connection.
A lower reuse time limit risks losing the benefit of connection
reuse when the average connection and mail delivery latency exceeds
the reuse time limit. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="smtp_data_done_timeout">smtp_data_done_timeout</a>
(default: 600s)</DT><DD>


The Postfix SMTP client time limit for sending the SMTP ".", and
for receiving the remote SMTP server response.



When no response is received within the deadline, a warning is
logged that the mail may be delivered multiple times.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="smtp_data_init_timeout">smtp_data_init_timeout</a>
(default: 120s)</DT><DD>


The Postfix SMTP client time limit for sending the SMTP DATA command,
and for receiving the remote SMTP server response.



Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).


</DD>

<DT><a name="smtp_data_xfer_timeout">smtp_data_xfer_timeout</a>
(default: 180s)</DT><DD>


The Postfix SMTP client time limit for sending the SMTP message content.
When the connection makes no progress for more than $<a href="postconf.5.html#smtp_data_xfer_timeout">smtp_data_xfer_timeout</a>
seconds the Postfix SMTP client terminates the transfer.



Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds).


</DD>

<DT><a name="smtp_defer_if_no_mx_address_found">smtp_defer_if_no_mx_address_found</a>
(default: no)</DT><DD>


Defer mail delivery when no MX record resolves to an IP address.



The default (no) is to return the mail as undeliverable. With older
Postfix versions the default was to keep trying to deliver the mail
until someone fixed the MX record or until the mail was too old.



Note: the Postfix SMTP client always ignores MX records with equal
or worse preference
than the local MTA itself.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="smtp_delivery_status_filter">smtp_delivery_status_filter</a>
(default: $<a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a>)</DT><DD>

 Optional filter for the <a href="smtp.8.html">smtp(8)</a> delivery agent to change the
delivery status code or explanatory text of successful or unsuccessful
deliveries. See <a href="postconf.5.html#default_delivery_status_filter">default_delivery_status_filter</a> for details. 

 NOTE: This feature modifies Postfix SMTP client error or non-error
messages that may or may not be derived from remote SMTP server
responses. In contrast, the <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a> feature modifies
remote SMTP server responses only. 

</DD>

<DT><a name="smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a>
(default: $<a href="postconf.5.html#default_destination_concurrency_limit">default_destination_concurrency_limit</a>)</DT><DD>

 The maximal number of parallel deliveries to the same destination
via the smtp message delivery transport. This limit is enforced by
the queue manager. The message delivery transport name is the first
field in the entry in the <a href="master.5.html">master.cf</a> file. 

</DD>

<DT><a name="smtp_destination_recipient_limit">smtp_destination_recipient_limit</a>
(default: $<a href="postconf.5.html#default_destination_recipient_limit">default_destination_recipient_limit</a>)</DT><DD>

 The maximal number of recipients per message for the smtp
message delivery transport. This limit is enforced by the queue
manager. The message delivery transport name is the first field in
the entry in the <a href="master.5.html">master.cf</a> file. 

 Setting this parameter to a value of 1 changes the meaning of
<a href="postconf.5.html#smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a> from concurrency per domain
into concurrency per recipient. 

</DD>

<DT><a name="smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a>
(default: empty)</DT><DD>

 Lookup tables, indexed by the remote SMTP server address, with
case insensitive lists of EHLO keywords (pipelining, starttls, auth,
etc.) that the Postfix SMTP client will ignore in the EHLO response from a
remote SMTP server. See <a href="postconf.5.html#smtp_discard_ehlo_keywords">smtp_discard_ehlo_keywords</a> for details. The
table is not indexed by hostname for consistency with
<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_discard_ehlo_keywords">smtp_discard_ehlo_keywords</a>
(default: empty)</DT><DD>

 A case insensitive list of EHLO keywords (pipelining, starttls,
auth, etc.) that the Postfix SMTP client will ignore in the EHLO
response from a remote SMTP server. 

 This feature is available in Postfix 2.2 and later. 

 Notes: 

<ul>

<li> Specify the silent-discard pseudo keyword to prevent
this action from being logged. 

<li> Use the <a href="postconf.5.html#smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a> feature to
discard EHLO keywords selectively. 

</ul>

</DD>

<DT><a name="smtp_dns_reply_filter">smtp_dns_reply_filter</a>
(default: empty)</DT><DD>

 Optional filter for Postfix SMTP client DNS lookup results.
Specify zero or more lookup tables. The lookup tables are searched
in the given order for a match with the DNS lookup result, converted
to the following form: 

<pre>
 name ttl class type preference value
</pre>

 The class field is always "IN", the preference
field exists only for MX records, the names of hosts, domains, etc.
end in ".", and those names are in ASCII form (xn--mumble form in
the case of UTF8 names). 

 When a match is found, the table lookup result specifies an
action. By default, the table query and the action name are
case-insensitive. Currently, only the IGNORE action is
implemented. 

 Notes: 

<ul>

<li> Postfix DNS reply filters have no effect on implicit DNS
lookups through nsswitch.conf or equivalent mechanisms. 

<li> The Postfix SMTP/LMTP client uses <a href="postconf.5.html#smtp_dns_reply_filter">smtp_dns_reply_filter</a>
and <a href="postconf.5.html#lmtp_dns_reply_filter">lmtp_dns_reply_filter</a> only to discover a remote SMTP or LMTP
service (record types MX, A, AAAA, and TLSA). These lookups are
also made to implement the features <a href="postconf.5.html#reject_unverified_sender">reject_unverified_sender</a> and
<a href="postconf.5.html#reject_unverified_recipient">reject_unverified_recipient</a>. 

<li> The Postfix SMTP/LMTP client defers mail delivery when
a filter removes all lookup results from a successful query. 

<li> Postfix SMTP server uses <a href="postconf.5.html#smtpd_dns_reply_filter">smtpd_dns_reply_filter</a> only to
look up MX, A, AAAA, and TXT records to implement the features
<a href="postconf.5.html#reject_unknown_helo_hostname">reject_unknown_helo_hostname</a>, <a href="postconf.5.html#reject_unknown_sender_domain">reject_unknown_sender_domain</a>,
<a href="postconf.5.html#reject_unknown_recipient_domain">reject_unknown_recipient_domain</a>, reject_rbl_*, and reject_rhsbl_*.


<li> The Postfix SMTP server logs a warning or defers mail
delivery when a filter removes all lookup results from a successful
query. 

</ul>

 Example: ignore Google AAAA records in Postfix SMTP client DNS
lookups, because Google sometimes hard-rejects mail from IPv6 clients
with valid PTR etc. records. 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#smtp_dns_reply_filter">smtp_dns_reply_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/smtp_dns_reply_filter
</pre>

<pre>
/etc/postfix/smtp_dns_reply_filter:
 # /domain ttl IN AAAA address/ action, all case-insensitive.
 # Note: the domain name ends in ".".
 /^\S+\.google\.com\.\s+\S+\s+\S+\s+AAAA\s+/ IGNORE
</pre>

 This feature is available in Postfix 3.0 and later. 

</DD>

<DT><a name="smtp_dns_resolver_options">smtp_dns_resolver_options</a>
(default: empty)</DT><DD>

 DNS Resolver options for the Postfix SMTP client. Specify zero
or more of the following options, separated by comma or whitespace.
Option names are case-sensitive. Some options refer to domain names
that are specified in the file /etc/resolv.conf or equivalent. 

<dl>

<dt>res_defnames</dt>

<dd> Append the current domain name to single-component names (those
that do not contain a "." character). This can produce incorrect
results, and is the hard-coded behavior prior to Postfix 2.8. </dd>

<dt>res_dnsrch</dt>

<dd> Search for host names in the current domain and in parent
domains. This can produce incorrect results and is therefore not
recommended. </dd>

</dl>

 This feature is available in Postfix 2.8 and later. 

</DD>

<DT><a name="smtp_dns_support_level">smtp_dns_support_level</a>
(default: empty)</DT><DD>

 Level of DNS support in the Postfix SMTP client. With
"<a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>" left at its empty default value, the legacy
"<a href="postconf.5.html#disable_dns_lookups">disable_dns_lookups</a>" parameter controls whether DNS is enabled in
the Postfix SMTP client, otherwise the legacy parameter is ignored.


 Specify one of the following: 

<dl>

<dt>disabled</dt>

<dd>Disable DNS lookups. No MX lookups are performed and hostname
to address lookups are unconditionally "native". This setting is
not appropriate for hosts that deliver mail to the public Internet.
Some obsolete how-to documents recommend disabling DNS lookups in
some configurations with content_filters. This is no longer required
and strongly discouraged. </dd>

<dt>enabled</dt>

<dd>Enable DNS lookups. Nexthop destination domains not enclosed
in "[]" will be subject to MX lookups. If "dns" and "native" are
included in the "<a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a>" parameter value, DNS will be
queried first to resolve MX-host A records, followed by "native"
lookups if no answer is found in DNS. </dd>

<dt>dnssec</dt>

<dd>Enable <a href="https://tools.ietf.org/html/rfc4033">DNSSEC</a>
lookups. The "dnssec" setting differs from the "enabled" setting
above in the following ways: <ul> <li>Any MX lookups will set
RES_USE_DNSSEC and RES_USE_EDNS0 to request DNSSEC-validated
responses. If the MX response is DNSSEC-validated the corresponding
hostnames are considered validated. <li> The address lookups of
validated hostnames are also validated, (provided of course
"<a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a>" includes "dns", see below). <li>Temporary
failures in DNSSEC-enabled hostname-to-address resolution block any
"native" lookups. Additional "native" lookups only happen when
DNSSEC lookups hard-fail (NODATA or NXDOMAIN). </ul> </dd>

</dl>

 The Postfix SMTP client considers non-MX "[nexthop]" and
"[nexthop]:port" destinations equivalent to statically-validated
MX records of the form "nexthop. IN MX 0 nexthop." Therefore,
with "dnssec" support turned on, validated hostname-to-address
lookups apply to the nexthop domain of any "[nexthop]" or
"[nexthop]:port" destination. This is also true for LMTP "inet:host"
and "inet:host:port" destinations, as LMTP hostnames are never
subject to MX lookups. 

The "dnssec" setting is recommended only if you plan to use the
<a href="TLS_README.html#client_tls_dane">dane</a> or <a
href="TLS_README.html#client_tls_dane">dane-only</a> TLS security
level, otherwise enabling DNSSEC support in Postfix offers no
additional security. Postfix DNSSEC support relies on an upstream
recursive nameserver that validates DNSSEC signatures. Such a DNS
server will always filter out forged DNS responses, even when Postfix
itself is not configured to use DNSSEC. 

 When using Postfix DANE support the "<a href="postconf.5.html#smtp_host_lookup">smtp_host_lookup</a>" parameter
should include "dns", as <a
href="https://tools.ietf.org/html/rfc7672">DANE</a> is not applicable
to hosts resolved via "native" lookups. 

 As mentioned above, Postfix is not a validating <a
href="https://tools.ietf.org/html/rfc4035#section-4.9">stub
resolver</a>; it relies on the system's configured DNSSEC-validating
<a href="https://tools.ietf.org/html/rfc4035#section-3.2">recursive
nameserver</a> to perform all DNSSEC validation. Since this
nameserver's DNSSEC-validated responses will be fully trusted, it
is strongly recommended that the MTA host have a local DNSSEC-validating
recursive caching nameserver listening on a loopback address, and
be configured to use only this nameserver for all lookups. Otherwise,
Postfix may remain subject to man-in-the-middle attacks that forge
responses from the recursive nameserver

DNSSEC support requires a version of Postfix compiled against a
reasonably-modern DNS resolver(3) library that implements the
RES_USE_DNSSEC and RES_USE_EDNS0 resolver options. 

 This feature is available in Postfix 2.11 and later. 

</DD>

<DT><a name="smtp_enforce_tls">smtp_enforce_tls</a>
(default: no)</DT><DD>

 Enforcement mode: require that remote SMTP servers use TLS
encryption, and never send mail in the clear. This also requires
that the remote SMTP server hostname matches the information in
the remote server certificate, and that the remote SMTP server
certificate was issued by a CA that is trusted by the Postfix SMTP
client. If the certificate doesn't verify or the hostname doesn't
match, delivery is deferred and mail stays in the queue. 

 The server hostname is matched against all names provided as
dNSNames in the SubjectAlternativeName. If no dNSNames are specified,
the CommonName is checked. The behavior may be changed with the
<a href="postconf.5.html#smtp_tls_enforce_peername">smtp_tls_enforce_peername</a> option. 

 This option is useful only if you are definitely sure that you
will only connect to servers that support <a href="https://tools.ietf.org/html/rfc2487">RFC 2487</a> _and_ that
provide valid server certificates. Typical use is for clients that
send all their email to a dedicated mailhub. 

 This feature is available in Postfix 2.2 and later. With
Postfix 2.3 and later use <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> instead. 

</DD>

<DT><a name="smtp_fallback_relay">smtp_fallback_relay</a>
(default: $<a href="postconf.5.html#fallback_relay">fallback_relay</a>)</DT><DD>

 Optional list of relay destinations that will be used when an
SMTP destination is not found, or when delivery fails due to a
non-permanent error. With Postfix 2.2 and earlier this parameter
is called <a href="postconf.5.html#fallback_relay">fallback_relay</a>. 

 By default, <a href="postconf.5.html#smtp_fallback_relay">smtp_fallback_relay</a> is empty, mail is returned to
the sender when a destination is not found, and delivery is deferred
after it fails due to a non-permanent error. 

 With bulk email deliveries, it can be beneficial to run the
fallback relay MTA on the same host, so that it can reuse the sender
IP address. This speeds up deliveries that are delayed by IP-based
reputation systems (greylist, etc.). 

 The fallback relays must be SMTP destinations. Specify a domain,
host, host:port, [host]:port, [address] or [address]:port; the form
[host] turns off MX lookups. If you specify multiple SMTP
destinations, Postfix will try them in the specified order. 

 To prevent mailer loops between MX hosts and fall-back hosts,
Postfix version 2.2 and later will not use the fallback relays for
destinations that it is MX host for (assuming DNS lookup is turned on).


</DD>

<DT><a name="smtp_generic_maps">smtp_generic_maps</a>
(default: empty)</DT><DD>

 Optional lookup tables that perform address rewriting in the
Postfix SMTP client, typically to transform a locally valid address into
a globally valid address when sending mail across the Internet.
This is needed when the local machine does not have its own Internet
domain name, but uses something like localdomain.local
instead. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


 The table format and lookups are documented in <a href="generic.5.html">generic(5)</a>;
examples are shown in the <a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a> and
<a href="STANDARD_CONFIGURATION_README.html">STANDARD_CONFIGURATION_README</a> documents. 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_header_checks">smtp_header_checks</a>
(default: empty)</DT><DD>

 Restricted <a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP client.
These tables are searched while mail is being delivered. Actions
that change the delivery time or destination are not available.


 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="smtp_helo_name">smtp_helo_name</a>
(default: $<a href="postconf.5.html#myhostname">myhostname</a>)</DT><DD>


The hostname to send in the SMTP HELO or EHLO command.



The default value is the machine hostname. Specify a hostname or
[ip.add.re.ss].



This information can be specified in the <a href="postconf.5.html">main.cf</a> file for all SMTP
clients, or it can be specified in the <a href="master.5.html">master.cf</a> file for a specific
client, for example:


<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
 mysmtp ... smtp -o <a href="postconf.5.html#smtp_helo_name">smtp_helo_name</a>=foo.bar.com
</pre>
</blockquote>


This feature is available in Postfix 2.0 and later.


</DD>

<DT><a name="smtp_helo_timeout">smtp_helo_timeout</a>
(default: 300s)</DT><DD>


The Postfix SMTP client time limit for sending the HELO or EHLO command,
and for receiving the initial remote SMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="smtp_host_lookup">smtp_host_lookup</a>
(default: dns)</DT><DD>


What mechanisms the Postfix SMTP client uses to look up a host's
IP address. This parameter is ignored when DNS lookups are disabled
(see: <a href="postconf.5.html#disable_dns_lookups">disable_dns_lookups</a> and <a href="postconf.5.html#smtp_dns_support_level">smtp_dns_support_level</a>). The "dns"
mechanism is always tried before "native" if both are listed.



Specify one of the following:


<dl>

<dt>dns</dt>

<dd>Hosts can be found in the DNS (preferred). </dd>

<dt>native</dt>

<dd>Use the native naming service only (nsswitch.conf, or equivalent
mechanism). </dd>

<dt>dns, native</dt>

<dd>Use the native service for hosts not found in the DNS. </dd>

</dl>


This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="smtp_line_length_limit">smtp_line_length_limit</a>
(default: 998)</DT><DD>


The maximal length of message header and body lines that Postfix
will send via SMTP. This limit does not include the <CR><LF>
at the end of each line. Longer lines are broken by inserting
"<CR><LF><SPACE>", to minimize the damage to MIME
formatted mail. Specify zero to disable this limit.



The Postfix limit of 998 characters not including <CR><LF>
is consistent with the SMTP limit of 1000 characters including
<CR><LF>. The Postfix limit was 990 with Postfix 2.8
and earlier.


</DD>

<DT><a name="smtp_log_tls_feature_status">smtp_log_tls_feature_status</a>
(default: yes)</DT><DD>

 Enable logging of TLS feature information in delivery status
logging. This summarizes how features such as TLS and REQUIRETLS
were used. A list of examples is at the end of this text. 

<ul>

<li> The logging is inserted between the "<tt>delays=a/b/c/d</tt>"
and the "<tt>dsn=x.y.z, status=...</tt>" information. 

<li> The general format is "<tt>tls=feature/feature/...</tt>".
See below for examples. 

<li> The first feature name is the TLS security level:
'<tt>none</tt>', '<tt>may</tt>', '<tt>encrypt</tt>', etc. Other
features are shown only if activated. The REQUIRETLS extension's
feature name is '<tt>requiretls</tt>'. 

<li> When a '<tt>:downgrade-level</tt>' is appended to
a feature name, the feature was downgraded to the indicated level.
A downgrade-level <tt>none</tt> indicates that the feature
was unavailable. The result of a downgrade may violate a strict
policy, but may still be compliant with a permissive policy. 

<li> When "<tt>!</tt>" is prepended to a feature, the policy
for that feature was violated and the connection was not used.


<li> When "?" is appended to a feature, the policy for that
feature was undecided. This is typically the result of a lost
connection or an incorrect configuration. 

</ul>

 Examples for TLS security levels: 

<dl>

<dt> tls=none </dt> <dd> A connection with TLS disabled. </dd>

<dt> tls=may </dt> <dd> Opportunistic TLS. The connection was used
after a successful TLS handshake. </dd>

<dt> tls=may? </dt> <dd> Opportunistic TLS. The status was undecided
because no connection was made, or no server could be reached. </dd>

<dt> tls=may:none </dt> <dd> Opportunistic TLS. The client was
willing to use TLS, but the remote server did not support STARTTLS,
and the connection was used in plaintext as permitted by the
opportunistic TLS policy. </dd>

<dt> tls=dane </dt> <dd> DANE policy compliant, no downgrade. </dd>

<dt> tls=dane:halfdane </dt> <dd> Opportunistic DANE. The connection
security was downgraded to '<tt>halfdane</tt>' to indicate that
mail server records were not DNSSEC-signed. </dd>

<dt> tls=dane:encrypt </dt> <dd> Opportunistic DANE. The connection
security was downgraded to '<tt>encrypt</tt>' because none of the TLSA
records were usable. </dd>

<dt> tls=dane? </dt> <dd> DANE policy status was undecided, because the
connection failed before or in the TLS handshake. </dd>

</dl>

 Examples for REQUIRETLS policies (set with <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a>),
where "<tt>xxx</tt>" is a TLS security level: 

<dl>

<dt> tls=xxx/requiretls </dt> <dd> 'Enforce' policy compliant.
After a successful TLS handshake that required a certificate match,
the remote server announced REQUIRETLS support, and the client sent
REQUIRETLS.

<dt> tls=xxx/!requiretls:nocertmatch </dt> <dd> 'Enforce' policy
violation. The connection was not used because the remote server
certificate did not match as required by the TLS security policy,
or no connection was made because the TLS security policy disabled
server certificate matching. </dd>

<dt> tls=xxx/requiretls:nocertmatch </dt> <dd> 'Opportunistic+starttls'
or 'opportunistic' policy compliant. After a successful TLS handshake
that did not require a server certificate match, the remote server
announced REQUIRETLS support, and the client sent REQUIRETLS. </dd>

<dt> tls=xxx/!requiretls:nostarttls </dt> <dd> 'Enforce' or
'opportunistic+starttls' policy violation. The connection was not
used because the remote server did not support STARTTLS. </dd>

<dt> tls=xxx/!requiretls:noencryption </dt> <dd> 'Enforce' or
'opportunistic+starttls' policy violation. No connection was made
because the TLS security policy disabled encryption. </dd>

<dt> tls=xxx/!requiretls:none </dt> <dd> 'Enforce' policy violation.
After a successful TLS handshake, the connection was not used because
the remote server did not support REQUIRETLS. </dd>

<dt> tls=xxx/requiretls:none </dt> <dd> 'Opportunistic+starttls'
policy compliant. After a successful TLS handshake, the remote
server did not announce REQUIRETLS support, and the connection was
used without sending REQUIRETLS. </dd>

<dt> tls=xxx/requiretls:none </dt> <dd> 'Opportunistic' policy
compliant. The remote server did not announce support for STARTTLS
or REQUIRETLS, and the connection was used without sending REQUIRETLS.
</dd>

<dt> tls=xxx/requiretls? </dt> <dd> Policy status was undecided,
because the connection failed before or in the TLS handshake, or
no connection was made due to a policy configuration error. </dd>

</dl>

 This feature is available in Postfix 3.11 and later. 

</DD>

<DT><a name="smtp_mail_timeout">smtp_mail_timeout</a>
(default: 300s)</DT><DD>


The Postfix SMTP client time limit for sending the MAIL FROM command,
and for receiving the remote SMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="smtp_mime_header_checks">smtp_mime_header_checks</a>
(default: empty)</DT><DD>

 Restricted mime_<a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP
client. These tables are searched while mail is being delivered.
Actions that change the delivery time or destination are not
available. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="smtp_min_data_rate">smtp_min_data_rate</a>
(default: 500)</DT><DD>

 The minimum plaintext data transfer rate in bytes/second for
DATA requests, when deadlines are enabled with <a href="postconf.5.html#smtp_per_request_deadline">smtp_per_request_deadline</a>.
After a write operation transfers N plaintext message bytes (possibly
after TLS encryption), and after the DATA request deadline is
decremented by the elapsed time of that write operation, the DATA
request deadline is incremented by N/smtp_min_data_rate seconds.
However, the deadline will never be incremented beyond the time
limit specified with <a href="postconf.5.html#smtp_data_xfer_timeout">smtp_data_xfer_timeout</a>. 

 This feature is available in Postfix 3.7 and later. 

</DD>

<DT><a name="smtp_mx_address_limit">smtp_mx_address_limit</a>
(default: 5)</DT><DD>


The maximal number of MX (mail exchanger) IP addresses that can
result from Postfix SMTP client mail exchanger lookups, or zero (no
limit). Prior to
Postfix version 2.3, this limit was disabled by default.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="smtp_mx_session_limit">smtp_mx_session_limit</a>
(default: 2)</DT><DD>

 The maximal number of SMTP sessions per delivery request before
the Postfix SMTP client
gives up or delivers to a fall-back <a href="postconf.5.html#relayhost">relay host</a>, or zero (no
limit). This restriction ignores sessions that fail to complete the
SMTP initial handshake (Postfix version 2.2 and earlier) or that fail to
complete the EHLO and TLS handshake (Postfix version 2.3 and later). 

 This feature is available in Postfix 2.1 and later. 

</DD>

<DT><a name="smtp_nested_header_checks">smtp_nested_header_checks</a>
(default: empty)</DT><DD>

 Restricted nested_<a href="header_checks.5.html">header_checks(5)</a> tables for the Postfix SMTP
client. These tables are searched while mail is being delivered.
Actions that change the delivery time or destination are not
available. 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="smtp_never_send_ehlo">smtp_never_send_ehlo</a>
(default: no)</DT><DD>

 Never send EHLO at the start of an SMTP session. See also the
<a href="postconf.5.html#smtp_always_send_ehlo">smtp_always_send_ehlo</a> parameter. 

</DD>

<DT><a name="smtp_per_record_deadline">smtp_per_record_deadline</a>
(default: no)</DT><DD>

 Change the behavior of the smtp_*_timeout time limits, from a
time limit per read or write system call, to a time limit to send
or receive a complete record (an SMTP command line, SMTP response
line, SMTP message content line, or TLS protocol message). This
limits the impact from hostile peers that trickle data one byte at
a time. 

 Note: when per-record deadlines are enabled, a short timeout
may cause problems with TLS over very slow network connections.
The reasons are that a TLS protocol message can be up to 16 kbytes
long (with TLSv1), and that an entire TLS protocol message must be
sent or received within the per-record deadline. 

 This feature is available in Postfix 2.9-3.6. With older
Postfix releases, the behavior is as if this parameter is set to
"no". Postfix 3.7 and later use <a href="postconf.5.html#smtp_per_request_deadline">smtp_per_request_deadline</a>. 

</DD>

<DT><a name="smtp_per_request_deadline">smtp_per_request_deadline</a>
(default: no)</DT><DD>

 Change the behavior of the smtp_*_timeout time limits, from a
time limit per plaintext or TLS read or write call, to a combined
time limit for sending a complete SMTP request and for receiving a
complete SMTP response. The deadline limits only the time spent
waiting for plaintext or TLS read or write calls, not time spent
elsewhere. The per-request deadline limits the impact from hostile
peers that trickle data one byte at a time. 

 See <a href="postconf.5.html#smtp_min_data_rate">smtp_min_data_rate</a> for how the per-request deadline is
managed during the DATA phase. 

 Note: when per-request deadlines are enabled, a short time limit
may cause problems with TLS over very slow network connections. The
reason is that a TLS protocol message can be up to 16 kbytes long
(with TLSv1), and that an entire TLS protocol message must be
transferred within the per-request deadline. 

 This feature is available in Postfix 3.7 and later. A weaker
feature, called <a href="postconf.5.html#smtp_per_record_deadline">smtp_per_record_deadline</a>, is available with Postfix
2.9-3.6. 

 This feature is available in Postfix 3.7 and later. 

</DD>

<DT><a name="smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a>
(default: 10s)</DT><DD>


How long the Postfix SMTP client pauses before sending
".<CR><LF>" in order to work around the PIX firewall
"<CR><LF>.<CR><LF>" bug.



Choosing too short a time makes this workaround ineffective when
sending large messages over slow network connections.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="smtp_pix_workaround_maps">smtp_pix_workaround_maps</a>
(default: empty)</DT><DD>

 Lookup tables, indexed by the remote SMTP server address, with
per-destination workarounds for CISCO PIX firewall bugs. The table
is not indexed by hostname for consistency with
<a href="postconf.5.html#smtp_discard_ehlo_keyword_address_maps">smtp_discard_ehlo_keyword_address_maps</a>. 


Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


 This feature is available in Postfix 2.4 and later. 

</DD>

<DT><a name="smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a>
(default: 500s)</DT><DD>

 How long a message must be queued before the Postfix SMTP client
turns on the PIX firewall "<CR><LF>.<CR><LF>"
bug workaround for delivery through firewalls with "smtp fixup"
mode turned on. 

 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 


By default, the workaround is turned off for mail that is queued
for less than 500 seconds. In other words, the workaround is normally
turned off for the first delivery attempt.



Specify 0 to enable the PIX firewall
"<CR><LF>.<CR><LF>" bug workaround upon the
first delivery attempt.


</DD>

<DT><a name="smtp_pix_workarounds">smtp_pix_workarounds</a>
(default: disable_esmtp, delay_dotcrlf)</DT><DD>

 A list that specifies zero or more workarounds for CISCO PIX
firewall bugs. These workarounds are implemented by the Postfix
SMTP client. Workaround names are separated by comma or space, and
are case insensitive. This parameter setting can be overruled with
per-destination <a href="postconf.5.html#smtp_pix_workaround_maps">smtp_pix_workaround_maps</a> settings. 

<dl>

<dt>delay_dotcrlf<dd> Insert a delay before sending
".<CR><LF>" after the end of the message content. The
delay is subject to the <a href="postconf.5.html#smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a> and
<a href="postconf.5.html#smtp_pix_workaround_threshold_time">smtp_pix_workaround_threshold_time</a> parameter settings. </dd>

<dt>disable_esmtp<dd> Disable all extended SMTP commands:
send HELO instead of EHLO. </dd>

</dl>

 This feature is available in Postfix 2.4 and later. The default
settings are backwards compatible with earlier Postfix versions.


</DD>

<DT><a name="smtp_quit_timeout">smtp_quit_timeout</a>
(default: 300s)</DT><DD>


The Postfix SMTP client time limit for sending the QUIT command,
and for receiving the remote SMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>
(default: yes)</DT><DD>


Quote addresses in Postfix SMTP client MAIL FROM and RCPT TO commands
as required
by <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>. This includes putting quotes around an address localpart
that ends in ".".



The default is to comply with <a href="https://tools.ietf.org/html/rfc5321">RFC 5321</a>. If you have to send mail to
a broken SMTP server, configure a special SMTP client in <a href="master.5.html">master.cf</a>:


<blockquote>
<pre>
/etc/postfix/<a href="master.5.html">master.cf</a>:
 broken-smtp . . . smtp -o <a href="postconf.5.html#smtp_quote_rfc821_envelope">smtp_quote_rfc821_envelope</a>=no
</pre>
</blockquote>


and route mail for the destination in question to the "broken-smtp"
message delivery with a <a href="transport.5.html">transport(5)</a> table.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="smtp_randomize_addresses">smtp_randomize_addresses</a>
(default: yes)</DT><DD>


Randomize the order of equal-preference MX host addresses. This
is a performance feature of the Postfix SMTP client.


</DD>

<DT><a name="smtp_rcpt_timeout">smtp_rcpt_timeout</a>
(default: 300s)</DT><DD>


The Postfix SMTP client time limit for sending the SMTP RCPT TO
command, and for receiving the remote SMTP server response.


 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

</DD>

<DT><a name="smtp_reply_filter">smtp_reply_filter</a>
(default: empty)</DT><DD>

 A mechanism to transform replies from remote SMTP servers one
line at a time. This is a last-resort tool to work around server
replies that break interoperability with the Postfix SMTP client.
Other uses involve fault injection to test Postfix's handling of
invalid responses. 

 Notes: 

<ul>

<li> In the case of a multi-line reply, the Postfix SMTP client
uses the final reply line's numerical SMTP reply code and enhanced
status code. 

<li> The numerical SMTP reply code (XYZ) takes precedence over
the enhanced status code (X.Y.Z). When the enhanced status code
initial digit differs from the SMTP reply code initial digit, or
when no enhanced status code is present, the Postfix SMTP client
uses a generic enhanced status code (X.0.0) instead. 

</ul>

 Specify the name of a "<a href="DATABASE_README.html">type:table</a>" lookup table. The search
string is a single SMTP reply line as received from the remote SMTP
server, except that the trailing <CR><LF> are removed.
When the lookup succeeds, the result replaces the single SMTP reply
line. 

 Examples: 

<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#smtp_reply_filter">smtp_reply_filter</a> = <a href="pcre_table.5.html">pcre</a>:/etc/postfix/reply_filter
</pre>

<pre>
/etc/postfix/reply_filter:
 # Some Microsoft servers violate <a href="https://tools.ietf.org/html/rfc2554">RFC 2554</a> section 4, causing Postfix
 # to complain with "non-empty initial GSSAPI challenge from server"
 /^334\s+GSSAPI\s+supported/ 334
</pre>

<pre>
 # Transform garbage into "250-filler..." so that it looks like
 # one line from a multi-line reply. It does not matter what we
 # substitute here as long it has the right syntax. The Postfix
 # SMTP client will use the final line's numerical SMTP reply
 # code and enhanced status code.
 !/^([2-5][0-9][0-9]($|[- ]))/ 250-filler for garbage
</pre>

 This feature is available in Postfix 2.7. 

</DD>

<DT><a name="smtp_requiretls_policy">smtp_requiretls_policy</a>
(default: see 'postconf -d <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a>' output)</DT><DD>

 How the Postfix SMTP and LMTP client will enforce REQUIRETLS
for messages received with the REQUIRETLS option. Policy examples
for SMTP and LMTP are at the end. 

<ul>

<li> Specify a list of items, separated with whitespace or
comma; continue a long line by starting the next line with whitespace.


<li> Each item must be an action (see below), or a <a href="DATABASE_README.html">type:table</a>
lookup table that must return an action (it must not return a
<a href="DATABASE_README.html">type:table</a>). 

<li> In the text that follows, the TLS next-hop destination for
TCP connections is the recipient domain by default, but this can
be overruled with destinations specified with <a href="postconf.5.html#transport_maps">transport_maps</a>,
<a href="postconf.5.html#relayhost">relayhost</a>, <a href="postconf.5.html#content_filter">content_filter</a>, or other routing features. The next-hop
destination for LMTP over UNIX-domain connections is always the
value of <a href="postconf.5.html#myhostname">myhostname</a>. 

<li> A <a href="DATABASE_README.html">type:table</a> lookup table is searched with the TLS next-hop
destination (without any [ ], :service, or :port).
A non-ASCII next-hop destination is converted into ASCII form
(Punycode) before making a policy query; lookup tables must answer
ASCII-form queries. 

<li> A fixed-string table (such as <a href="lmdb_table.5.html">lmdb</a>:, <a href="CDB_README.html">cdb</a>:, or <a href="DATABASE_README.html#types">hash</a>:) is
also searched with the next-hop ".parent" domains (in a table key,
prepend a '.' to a parent domain name). These ".parent" domain
queries are not made with pattern-based lookup tables such as <a href="regexp_table.5.html">regexp</a>:
or <a href="pcre_table.5.html">pcre</a>: or with <a href="socketmap_table.html">socketmap</a>: or <a href="tcp_table.5.html">tcp</a>: tables. 

</ul>

 Supported actions, assuming that TLS feature status logging is
enabled with "<a href="postconf.5.html#smtp_log_tls_feature_status">smtp_log_tls_feature_status</a> = yes" (the default): 

<dl>

<dt> enforce </dt> <dd> Skip servers that do not support
STARTTLS, skip connections without a server certificate match, and
skip servers that don't support REQUIRETLS after STARTTLS. 
If a suitable server is found, request REQUIRETLS, deliver the
message, and log "<tt>tls=level/requiretls</tt>" in delivery
status logging, where <tt>level</tt> shows the current SMTP
client TLS security level. If no suitable server is found,
return the message as undeliverable and log a policy violation
"<tt>tls=level/!requiretls:nocertmatch</tt>",
"<tt>tls=level/!requiretls:noencryption</tt>", or
"<tt>tls=level/!requiretls:nostarttls</tt>", as described
under <a href="postconf.5.html#smtp_log_tls_feature_status">smtp_log_tls_feature_status</a>. NOTE: this is also used
implicitly when no REQUIRETLS policy match is found. </dd>

<dt> opportunistic+starttls </dt> <dd> Skip servers
that don't announce STARTTLS support, but do not require a server
certificate match or remote REQUIRETLS support. If a
suitable server is found, send REQUIRETLS if that server supports
REQUIRETLS and log "<tt>tls=level/requiretls</tt>" or
"<tt>tls=level/requiretls:nomatch</tt>" in delivery status
logging, or simply deliver the message as if the sender did not
request REQUIRETLS and log "<tt>tls=level/requiretls:none</tt>,
where <tt>level</tt> shows the current SMTP client TLS
security level. If no suitable server is found, return the
message as undeliverable and log a policy violation
"<tt>tls=level/!requiretls:noencryption</tt>" or
"<tt>tls=level/!requiretls:nostarttls</tt>" as described
under <a href="postconf.5.html#smtp_log_tls_feature_status">smtp_log_tls_feature_status</a>. This relaxed policy can
be appropriate for an outbound perimeter MTA, when forwarding
messages from internal systems to the Internet, at a time that many
domains support TLS but have no DANE or MTA-STS policies. </dd>

<dt> opportunistic </dt> <dd> Do not require STARTTLS,
a server certificate match, or remote REQUIRETLS support. 
Request REQUIRETLS if the server supports both STARTTLS and REQUIRETLS
and log "<tt>tls=level/requiretls</tt>" or
"<tt>tls=level/requiretls:nomatch</tt>" in delivery status
logging, otherwise simply deliver the message as if the sender did
not request REQUIRETLS and log "<tt>tls=level/requiretls:none</tt>,
where <tt>level</tt> shows the current SMTP client TLS
security level. This REQUIRETLS policy is non-intrusive,
because there can be no REQUIRETLS policy violation. This
weak policy can be appropriate for an inbound perimeter MTA, when
forwarding messages from the Internet to internal servers or content
filters that may not support STARTTLS or REQUIRETLS, using internal
connections instead of the public Internet. This setting may also
be useful for an outbound MTA to discover what destinations support
some form of REQUIRETLS without risking mail delivery problems.
 </dd>

<dt> disable </dt> <dd> Disable REQUIRETLS support.
Deliver all messages as if the sender did not request REQUIRETLS.
This may be used as a last-resort workaround when a server announces
REQUIRETLS support, but the support is inoperable. </dd>

</dl>

 Notes: 

<ul>

<li> To match any name below the domain "example.com" specify
a table entry with the storage key ".example.com" in <a href="DATABASE_README.html">type:table</a>
lookup tables that need an exact match. This is appropriate, for
example, with <a href="lmdb_table.5.html">lmdb</a>:, <a href="CDB_README.html">cdb</a>: or <a href="DATABASE_README.html#types">hash</a>:. 

<li> Do not specify a match pattern for ".domain" with <a href="regexp_table.5.html">regexp</a>:,
<a href="pcre_table.5.html">pcre</a>:, <a href="socketmap_table.html">socketmap</a>:, or <a href="tcp_table.5.html">tcp</a>:, as <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> will
not query those tables with that form. 

</ul>

 SMTP client examples. See <a href="REQUIRETLS_README.html">REQUIRETLS_README</a> for discussion. 

<ul>

<li> The simplest policy: when a sender requests REQUIRETLS,
request REQUIRETLS when an external or internal server supports
both STARTTLS and REQUIRETLS (lines 4, 5), and enforce a TLS
certificate match only if the destination publishes a DANE or STS
policy (line 3). When the sender requests REQUIRETLS, and an external
or internal server does not support both STARTTLS and REQUIRETLS,
simply deliver the message as if the sender did not request REQUIRETLS
(lines 4, 5). 
<pre>
1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
2 <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = may
3 <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = ...dane/sts plugin...
4 <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> = opportunistic
5 <a href="postconf.5.html#lmtp_requiretls_policy">lmtp_requiretls_policy</a> = opportunistic
</pre>

<li> The default SMTP client REQUIRETLS policy (lines 4-12):
when a sender requests REQUIRETLS, require that an external server
supports STARTTLS and REQUIRETLS, and require that its server
certificate matches a DANE or STS policy (lines 3, 12); make
REQUIRETLS support optional for delivery to internal destinations
or content filters specified as a symbolic name (lines 5-8) or as
a numeric address (lines 9-11). An internationalized domain name
must be specified in ASCII form (lines 6-7); the default policy
below uses ${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} which returns $<a href="postconf.5.html#mydomain">mydomain</a>
when the domain name contains only ASCII characters, and which
returns Punycode (<tt>xn--mumble</tt>) when $<a href="postconf.5.html#mydomain">mydomain</a> contains
non-ASCII. Note: if you specify a domain list outside <a href="postconf.5.html">main.cf</a>, then
the automatic $name expansions and Punycode conversions will
not happen, and you will need to enter explicit ASCII domain
names.
<pre>
1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
2 <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = may
3 <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = ...dane/sts plugin...
4 <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> =
5 <a href="DATABASE_README.html#types">inline</a>:{
6 { ${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic }
7 { .${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic }
8 { localhost = opportunistic } }
9 <a href="cidr_table.5.html">cidr</a>:{
10 { 0.0.0.0/0 opportunistic },
11 { ::/0 opportunistic } },
12 enforce
</pre>

<li> An SMTP client REQUIRETLS policy that is relaxed for
external destinations (line 12): when a sender requests REQUIRETLS,
require that an external server supports STARTTLS but enforce a TLS
certificate match only if the receiver publishes a DANE or STS
policy (line 3), and do not require that an external server supports
REQUIRETLS. Copy the above policy for internal destinations or
content filters (lines 5-11). Again, an internationalized domain
name must be specified in ASCII form (lines 6-7); the policy uses
${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} which returns $<a href="postconf.5.html#mydomain">mydomain</a> when the
domain name contains only ASCII characters, and which returns
Punycode (<tt>xn--mumble</tt>) when $<a href="postconf.5.html#mydomain">mydomain</a> contains non-ASCII.
Note: if you specify a domain list outside <a href="postconf.5.html">main.cf</a>, then the automatic
$name expansions and Punycode conversions will not happen,
and you will need to enter explicit ASCII domain names.
<pre>
1 /etc/postfix/<a href="postconf.5.html">main.cf</a>:
2 <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = may
3 <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = ...dane/sts plugin...
4 <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> =
5 <a href="DATABASE_README.html#types">inline</a>:{
6 { ${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic }
7 { .${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic }
8 { localhost = opportunistic } }
9 <a href="cidr_table.5.html">cidr</a>:{
10 { 0.0.0.0/0 opportunistic },
11 { ::/0 opportunistic } },
12 opportunistic+starttls
</pre>

<li> As above, with external destinations listed in a separate
file for easier maintenance. 
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> = may
 <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> = ...dane/sts plugin...
 <a href="postconf.5.html#smtp_requiretls_policy">smtp_requiretls_policy</a> =
 <a href="DATABASE_README.html#types">inline</a>:{
 { ${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic }
 { .${<a href="postconf.5.html#domain_to_ascii">domain_to_ascii</a>{$<a href="postconf.5.html#mydomain">mydomain</a>}} = opportunistic }
 { localhost = opportunistic } }
 <a href="cidr_table.5.html">cidr</a>:{
 { 0.0.0.0/0 opportunistic },
 { ::/0 opportunistic } },
 <a href="lmdb_table.5.html">lmdb</a>:/etc/postfix/requiretls-per-site
 opportunistic+starttls
</pre>
<pre>
/etc/postfix/requiretls-per-site:
 one.example enforce
 two.example enforce
 three.example opportunistic
 ...
</pre>

 Instead of <a href="lmdb_table.5.html">lmdb</a>:, some systems use <a href="CDB_README.html">cdb</a>:, <a href="DATABASE_README.html#types">hash</a>:, or <a href="DATABASE_README.html#types">dbm</a>:. 

 Execute the command "postmap /etc/postfix/requiretls-per-site"
after you change the requiretls-per-site file, to (re)build a
default-type indexed file. Execute "postmap
type:/etc/postfix/requiretls-per-site" to specify an explicit
type. 

 The default indexed file type is configured with the
<a href="postconf.5.html#default_database_type">default_database_type</a> parameter. To list available explicit types,
execute the command "postconf -m". 

 Configuration changes will become visible after a minute or so.
Use "postfix reload" to eliminate the delay. 

</ul>


LMTP client examples. See <a href="REQUIRETLS_README.html">REQUIRETLS_README</a> for discussion.


<ul>

<li> The default LMTP client REQUIRETLS policy: when a sender
requests REQUIRETLS, request REQUIRETLS if the server supports
REQUIRETLS, otherwise deliver the message as if the sender did not
request REQUIRETLS. Note: with deliveries over a UNIX-domain socket,
the next-hop destination for <a href="postconf.5.html#lmtp_requiretls_policy">lmtp_requiretls_policy</a> lookups will
be the <a href="postconf.5.html#myhostname">myhostname</a> parameter value. 
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#lmtp_requiretls_policy">lmtp_requiretls_policy</a> = opportunistic
</pre>

</ul>

 This feature is available in Postfix ≥ 3.11. 

</DD>

<DT><a name="smtp_rset_timeout">smtp_rset_timeout</a>
(default: 20s)</DT><DD>

 The Postfix SMTP client time limit for sending the RSET command,
and for receiving the remote SMTP server response. The SMTP client
sends RSET in
order to finish a recipient address probe, or to verify that a
cached session is still usable. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.1 and later. 

</DD>

<DT><a name="smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
(default: empty)</DT><DD>

 An optional table to prevent repeated SASL authentication
failures with the same remote SMTP server hostname, username and
password. Each table (key, value) pair contains a server name, a
username and password, and the full server response. This information
is stored when a remote SMTP server rejects an authentication attempt
with a 535 reply code. As long as the <a href="postconf.5.html#smtp_sasl_password_maps">smtp_sasl_password_maps</a>
information does not change, and as long as the <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a>
information does not expire (see <a href="postconf.5.html#smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>) the
Postfix SMTP client avoids SASL authentication attempts with the
same server, username and password, and instead bounces or defers
mail as controlled with the <a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> configuration
parameter. 

 Use a per-destination delivery concurrency of 1 (for example,
"<a href="postconf.5.html#smtp_destination_concurrency_limit">smtp_destination_concurrency_limit</a> = 1",
"<a href="postconf.5.html#relay_destination_concurrency_limit">relay_destination_concurrency_limit</a> = 1", etc.), otherwise multiple
delivery agents may experience a login failure at the same time.


 The table must be accessed via the proxywrite service, i.e. the
map name must start with "<a href="proxymap.8.html">proxy</a>:". The table should be stored under
the directory specified with the <a href="postconf.5.html#data_directory">data_directory</a> parameter. 

 This feature uses cryptographic hashing to protect plain-text
passwords, and requires that Postfix is compiled with TLS support.


 Examples: 

<pre>
<a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a> = <a href="proxymap.8.html">proxy</a>:<a href="lmdb_table.5.html">lmdb</a>:/var/lib/postfix/sasl_auth_cache
<a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a> = <a href="proxymap.8.html">proxy</a>:<a href="DATABASE_README.html#types">btree</a>:/var/lib/postfix/sasl_auth_cache
</pre>

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="smtp_sasl_auth_cache_time">smtp_sasl_auth_cache_time</a>
(default: 90d)</DT><DD>

 The maximal age of an <a href="postconf.5.html#smtp_sasl_auth_cache_name">smtp_sasl_auth_cache_name</a> entry before it
is removed. 

 Specify a non-negative time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is d (days). 

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="smtp_sasl_auth_enable">smtp_sasl_auth_enable</a>
(default: no)</DT><DD>


Enable SASL authentication in the Postfix SMTP client. By default,
the Postfix SMTP client uses no authentication.



Example:


<pre>
<a href="postconf.5.html#smtp_sasl_auth_enable">smtp_sasl_auth_enable</a> = yes
</pre>

</DD>

<DT><a name="smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a>
(default: yes)</DT><DD>

 When a remote SMTP server rejects a SASL authentication request
with a 535 reply code, defer mail delivery instead of returning
mail as undeliverable. The latter behavior was hard-coded prior to
Postfix version 2.5. 

 Note: the setting "yes" overrides the global <a href="postconf.5.html#soft_bounce">soft_bounce</a>
parameter, but the setting "no" does not. 

 Example: 

<pre>
# Default as of Postfix 2.5
<a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> = yes
# The old hard-coded default
<a href="postconf.5.html#smtp_sasl_auth_soft_bounce">smtp_sasl_auth_soft_bounce</a> = no
</pre>

 This feature is available in Postfix 2.5 and later. 

</DD>

<DT><a name="smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a>
(default: empty)</DT><DD>


If non-empty, a Postfix SMTP client filter for the remote SMTP
server's list of offered SASL mechanisms. Different client and
server implementations may support different mechanism lists; by
default, the Postfix SMTP client will use the intersection of the
two. <a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> specifies an optional third mechanism
list to intersect with. 

 Specify mechanism names, "/file/name" patterns or "<a href="DATABASE_README.html">type:table</a>"
lookup tables. The right-hand side result from "<a href="DATABASE_README.html">type:table</a>" lookups
is ignored. Specify "!pattern" to exclude a mechanism name from the
list. The form "!/file/name" is supported only in Postfix version
2.4 and later. 

 This feature is available in Postfix 2.2 and later. 


Examples:


<pre>
<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = plain, login
<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = /etc/postfix/smtp_mechs
<a href="postconf.5.html#smtp_sasl_mechanism_filter">smtp_sasl_mechanism_filter</a> = !gssapi, !login, <a href="DATABASE_README.html#types">static</a>:rest
</pre>

</DD>

<DT><a name="smtp_sasl_password_maps">smtp_sasl_password_maps</a>
(default: empty)</DT><DD>


Optional Postfix SMTP client lookup tables with one username:password
entry per sender, remote hostname or next-hop domain. Per-sender
lookup is done only when sender-dependent authentication is enabled.
If no username:password entry is found, then the Postfix SMTP client
will not attempt to authenticate to the remote host.


 Use <a href="postconf.5.html#smtp_sasl_password_result_delimiter">smtp_sasl_password_result_delimiter</a> to specify an
alternative separator between username and password. 


The Postfix SMTP client opens the lookup table before going to
chroot jail, so you can leave the password file in /etc/postfix.



Specify zero or more "type:name" lookup tables, separated by
whitespace or comma. Tables will be searched in the specified order
until a match is found.


</DD>

<DT><a name="smtp_sasl_password_result_delimiter">smtp_sasl_password_result_delimiter</a>
(default: :)</DT><DD>

 The delimiter between username and password in sasl_passwd_maps lookup
results. Specify one non-whitespace character that does not appear in
the username. 

 This feature is available in Postfix ≥ 3.9. 

</DD>

<DT><a name="smtp_sasl_path">smtp_sasl_path</a>
(default: empty)</DT><DD>

 Implementation-specific information that the Postfix SMTP client
passes through to
the SASL plug-in implementation that is selected with
<a href="postconf.5.html#smtp_sasl_type">smtp_sasl_type</a>. Typically this specifies the name of a
configuration file or rendezvous point. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="smtp_sasl_security_options">smtp_sasl_security_options</a>
(default: noplaintext, noanonymous)</DT><DD>

 Postfix SMTP client SASL security options; as of Postfix 2.3
the list of available
features depends on the SASL client implementation that is selected
with <a href="postconf.5.html#smtp_sasl_type">smtp_sasl_type</a>. 

 The following security features are defined for the cyrus
client SASL implementation: 


Specify zero or more of the following:


<dl>

<dt>noplaintext</dt>

<dd>Disallow methods that use plaintext passwords. </dd>

<dt>noactive</dt>

<dd>Disallow methods subject to active (non-dictionary) attack.
</dd>

<dt>nodictionary</dt>

<dd>Disallow methods subject to passive (dictionary) attack. </dd>

<dt>noanonymous</dt>

<dd>Disallow methods that allow anonymous authentication. </dd>

<dt>mutual_auth</dt>

<dd>Only allow methods that provide mutual authentication (not
available with SASL version 1). </dd>

</dl>


Example:


<pre>
<a href="postconf.5.html#smtp_sasl_security_options">smtp_sasl_security_options</a> = noplaintext
</pre>

</DD>

<DT><a name="smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>
(default: $<a href="postconf.5.html#smtp_sasl_security_options">smtp_sasl_security_options</a>)</DT><DD>

 The SASL authentication security options that the Postfix SMTP
client uses for TLS encrypted SMTP sessions. 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a>
(default: $<a href="postconf.5.html#smtp_sasl_tls_security_options">smtp_sasl_tls_security_options</a>)</DT><DD>

 The SASL authentication security options that the Postfix SMTP
client uses for TLS encrypted SMTP sessions with a verified server
certificate. 

 When mail is sent to the public MX host for the recipient's
domain, server certificates are by default optional, and delivery
proceeds even if certificate verification fails. For delivery via
a submission service that requires SASL authentication, it may be
appropriate to send plaintext passwords only when the connection
to the server is strongly encrypted and the server identity
is verified. 

 The <a href="postconf.5.html#smtp_sasl_tls_verified_security_options">smtp_sasl_tls_verified_security_options</a> parameter makes it
possible to only enable plaintext mechanisms when a secure connection
to the server is available. Submission servers subject to this
policy must either have verifiable certificates or offer suitable
non-plaintext SASL mechanisms. 

 This feature is available in Postfix 2.6 and later. 

</DD>

<DT><a name="smtp_sasl_type">smtp_sasl_type</a>
(default: cyrus)</DT><DD>

 The SASL plug-in type that the Postfix SMTP client should use
for authentication. The available types are listed with the
"postconf -A" command. 

 This feature is available in Postfix 2.3 and later. 

</DD>

<DT><a name="smtp_send_dummy_mail_auth">smtp_send_dummy_mail_auth</a>
(default: no)</DT><DD>

 Whether or not to append the "AUTH=<>" option to the MAIL
FROM command in SASL-authenticated SMTP sessions. The default is
not to send this, to avoid problems with broken remote SMTP servers.
Before Postfix 2.9 the behavior is as if "<a href="postconf.5.html#smtp_send_dummy_mail_auth">smtp_send_dummy_mail_auth</a>
= yes".

 This feature is available in Postfix 2.9 and later. 

</DD>

<DT><a name="smtp_send_xforward_command">smtp_send_xforward_command</a>
(default: no)</DT><DD>


Send the non-standard XFORWARD command when the Postfix SMTP server
EHLO response announces XFORWARD support.



This allows a Postfix SMTP delivery agent, used for injecting mail
into
a content filter, to forward the name, address, protocol and HELO
name of the original client to the content filter and downstream
queuing SMTP server. This can produce more useful logging than
localhost[127.0.0.1] etc.



This feature is available in Postfix 2.1 and later.


</DD>

<DT><a name="smtp_sender_dependent_authentication">smtp_sender_dependent_authentication</a>
(default: no)</DT><DD>


Enable sender-dependent authentication in the Postfix SMTP client; this is
available only with SASL authentication, and disables SMTP connection
caching to ensure that mail from different senders will use the
appropriate credentials. 


This feature is available in Postfix 2.3 and later.


</DD>

<DT><a name="smtp_skip_4xx_greeting">smtp_skip_4xx_greeting</a>
(default: yes)</DT><DD>


Skip SMTP servers that greet with a 4XX status code (go away, try
again later).



By default, the Postfix SMTP client moves on the next mail exchanger.
Specify
"<a href="postconf.5.html#smtp_skip_4xx_greeting">smtp_skip_4xx_greeting</a> = no" if Postfix should defer delivery
immediately.


 This feature is available in Postfix 2.0 and earlier.
Later Postfix versions always skip remote SMTP servers that greet
with a
4XX status code. 

</DD>

<DT><a name="smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a>
(default: yes)</DT><DD>


Skip remote SMTP servers that greet with a 5XX status code.


 By default, the Postfix SMTP client moves on the next mail
exchanger. Specify "<a href="postconf.5.html#smtp_skip_5xx_greeting">smtp_skip_5xx_greeting</a> = no" if Postfix should
bounce the mail immediately. Caution: the latter behavior appears
to contradict <a href="https://tools.ietf.org/html/rfc2821">RFC 2821</a>. 

</DD>

<DT><a name="smtp_skip_quit_response">smtp_skip_quit_response</a>
(default: yes)</DT><DD>


Do not wait for the response to the SMTP QUIT command.


</DD>

<DT><a name="smtp_starttls_timeout">smtp_starttls_timeout</a>
(default: 300s)</DT><DD>

 Time limit for Postfix SMTP client write and read operations
during TLS startup and shutdown handshake procedures. 

 Specify a non-zero time value (an integral value plus an optional
one-letter suffix that specifies the time unit). Time units: s
(seconds), m (minutes), h (hours), d (days), w (weeks).
The default time unit is s (seconds). 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_tcp_port">smtp_tcp_port</a>
(default: smtp)</DT><DD>


The default TCP port that the Postfix SMTP client connects to.
Specify a symbolic name (see services(5)) or a numeric port.


</DD>

<DT><a name="smtp_tls_CAfile">smtp_tls_CAfile</a>
(default: empty)</DT><DD>

 A file containing CA certificates of root CAs trusted to sign
either remote SMTP server certificates or intermediate CA certificates.
These are loaded into memory before the <a href="smtp.8.html">smtp(8)</a> client enters the
chroot jail. If the number of trusted roots is large, consider using
<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> instead, but note that the latter directory must be
present in the chroot jail if the <a href="smtp.8.html">smtp(8)</a> client is chrooted. This
file may also be used to augment the client certificate trust chain,
but it is best to include all the required certificates directly in
$<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> (or, Postfix ≥ 3.4 $<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>). 

 Specify "<a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a> = /path/to/system_CA_file" to use
ONLY the system-supplied default Certification Authority certificates.


 Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = no" to prevent Postfix from
appending the system-supplied default CAs and trusting third-party
certificates. 

 Example: 

<pre>
<a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a> = /etc/postfix/CAcert.pem
</pre>

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_tls_CApath">smtp_tls_CApath</a>
(default: empty)</DT><DD>

 Directory with PEM format Certification Authority certificates
that the Postfix SMTP client uses to verify a remote SMTP server
certificate. Don't forget to create the necessary "hash" links
with, for example, "$OPENSSL_HOME/bin/c_rehash /etc/postfix/certs".


 To use this option in chroot mode, this directory (or a copy)
must be inside the chroot jail. 

 Specify "<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> = /path/to/system_CA_directory" to
use ONLY the system-supplied default Certification Authority certificates.


 Specify "<a href="postconf.5.html#tls_append_default_CA">tls_append_default_CA</a> = no" to prevent Postfix from
appending the system-supplied default CAs and trusting third-party
certificates. 

 Example: 

<pre>
<a href="postconf.5.html#smtp_tls_CApath">smtp_tls_CApath</a> = /etc/postfix/certs
</pre>

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_tls_block_early_mail_reply">smtp_tls_block_early_mail_reply</a>
(default: no)</DT><DD>

 Try to detect a mail hijacking attack based on a TLS protocol
vulnerability (CVE-2009-3555), where an attacker prepends malicious
HELO, MAIL, RCPT, DATA commands to a Postfix SMTP client TLS session.
The attack would succeed with non-Postfix SMTP servers that reply
to the malicious HELO, MAIL, RCPT, DATA commands after negotiating
the Postfix SMTP client TLS session. 

 This feature is available in Postfix 2.7. 

</DD>

<DT><a name="smtp_tls_cert_file">smtp_tls_cert_file</a>
(default: empty)</DT><DD>

 File with the Postfix SMTP client RSA certificate in PEM format.
This file may also contain the Postfix SMTP client private RSA key, and
these may be the same as the Postfix SMTP server RSA certificate and key
file. With Postfix ≥ 3.4 the preferred way to configure client keys
and certificates is via the "<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>" parameter. 

 Do not configure client certificates unless you must present
client TLS certificates to one or more servers. Client certificates are
not usually needed, and can cause problems in configurations that work
well without them. The recommended setting is to let the defaults stand: 

<blockquote>
<pre>
<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> =
<a href="postconf.5.html#smtp_tls_key_file">smtp_tls_key_file</a> =
<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a> =
<a href="postconf.5.html#smtp_tls_eckey_file">smtp_tls_eckey_file</a> =
# Obsolete DSA parameters
<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> =
<a href="postconf.5.html#smtp_tls_dkey_file">smtp_tls_dkey_file</a> =
# Postfix ≥ 3.4 interface
<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> =
</pre>
</blockquote>

 The best way to use the default settings is to comment out the above
parameters in <a href="postconf.5.html">main.cf</a> if present. 

 To enable remote SMTP servers to verify the Postfix SMTP client
certificate, the issuing CA certificates must be made available to the
server. You should include the required certificates in the client
certificate file, the client certificate first, then the issuing
CA(s) (bottom-up order). 

 Example: the certificate for "client.example.com" was issued by
"intermediate CA" which itself has a certificate issued by "root CA".
As the "root" super-user create the client.pem file with: 

<blockquote>
<pre>
# umask 077
# cat client_key.pem client_cert.pem intermediate_CA.pem > chain.pem 
</pre>
</blockquote>

 If you also want to verify remote SMTP server certificates issued by
these CAs, you can add the CA certificates to the <a href="postconf.5.html#smtp_tls_CAfile">smtp_tls_CAfile</a>, in
which case it is not necessary to have them in the <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a>,
<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> (obsolete) or <a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a>. 

 A certificate supplied here must be usable as an SSL client certificate
and hence pass the "openssl verify -purpose sslclient ..." test. 

 Example: 

<pre>
<a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> = /etc/postfix/chain.pem
</pre>

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_tls_chain_files">smtp_tls_chain_files</a>
(default: empty)</DT><DD>

 List of one or more PEM files, each holding one or more private keys
directly followed by a corresponding certificate chain. The file names
are separated by commas and/or whitespace. This parameter obsoletes the
legacy algorithm-specific key and certificate file settings. When this
parameter is non-empty, the legacy parameters are ignored, and a warning
is logged if any are also non-empty. 

 With the proliferation of multiple private key algorithms—which,
as of OpenSSL 1.1.1, include DSA (obsolete), RSA, ECDSA, Ed25519
and Ed448—it is increasingly impractical to use separate
parameters to configure the key and certificate chain for each
algorithm. Therefore, Postfix now supports storing multiple keys and
corresponding certificate chains in a single file or in a set of files.

 Each key must appear immediately before the corresponding
certificate, optionally followed by additional issuer certificates that
complete the certificate chain for that key. When multiple files are
specified, they are equivalent to a single file that is concatenated
from those files in the given order. Thus, while a key must always
precede its certificate and issuer chain, it can be in a separate file,
so long as that file is listed immediately before the file that holds
the corresponding certificate chain. Once all the files are
concatenated, the sequence of PEM objects must be: key1, cert1,
[chain1], key2, cert2, [chain2], ..., keyN, certN, [chainN]. 

 Storing the private key in the same file as the corresponding
certificate is more reliable. With the key and certificate in separate
files, there is a chance that during key rollover a Postfix process
might load a private key and certificate from separate files that don't
match. Various operational errors may even result in a persistent
broken configuration in which the certificate does not match the private
key. 

 The file or files must contain at most one key of each type. If,
for example, two or more RSA keys and corresponding chains are listed,
depending on the version of OpenSSL either only the last one will be
used or a configuration error may be detected. Note that while
"Ed25519" and "Ed448" are considered separate algorithms, the various
ECDSA curves (typically one of prime256v1, secp384r1 or secp521r1) are
considered as different parameters of a single "ECDSA" algorithm, so it
is not presently possible to configure keys for more than one ECDSA
curve. 


Example (separate files for each key and corresponding certificate chain):

<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> =
 ${<a href="postconf.5.html#config_directory">config_directory</a>}/ed25519.pem,
 ${<a href="postconf.5.html#config_directory">config_directory</a>}/ed448.pem,
 ${<a href="postconf.5.html#config_directory">config_directory</a>}/rsa.pem
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/ed25519.pem:
 -----BEGIN PRIVATE KEY-----
 MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
 -----END PRIVATE KEY-----
 -----BEGIN CERTIFICATE-----
 MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
 ...
 nC0egv51YPDWxEHom4QA
 -----END CERTIFICATE-----
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/ed448.pem:
 -----BEGIN PRIVATE KEY-----
 MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
 LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
 -----END PRIVATE KEY-----
 -----BEGIN CERTIFICATE-----
 MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
 ...
 pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
 -----END CERTIFICATE-----
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/rsa.pem:
 -----BEGIN PRIVATE KEY-----
 MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
 ...
 ahQkZ3+krcaJvDSMgvu0tDc=
 -----END PRIVATE KEY-----
 -----BEGIN CERTIFICATE-----
 MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
 ...
 Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
 -----END CERTIFICATE-----
</pre>
</blockquote>


Example (all keys and certificates in a single file):

<blockquote>
<pre>
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
 <a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a> = ${<a href="postconf.5.html#config_directory">config_directory</a>}/chains.pem
</pre>
</blockquote>

<blockquote>
<pre>
/etc/postfix/chains.pem:
 -----BEGIN PRIVATE KEY-----
 MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
 -----END PRIVATE KEY-----
 -----BEGIN CERTIFICATE-----
 MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
 ...
 nC0egv51YPDWxEHom4QA
 -----END CERTIFICATE-----
 -----BEGIN PRIVATE KEY-----
 MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
 LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
 -----END PRIVATE KEY-----
 -----BEGIN CERTIFICATE-----
 MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
 ...
 pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
 -----END CERTIFICATE-----
 -----BEGIN PRIVATE KEY-----
 MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
 ...
 ahQkZ3+krcaJvDSMgvu0tDc=
 -----END PRIVATE KEY-----
 -----BEGIN CERTIFICATE-----
 MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
 ...
 Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
 -----END CERTIFICATE-----
</pre>
</blockquote>

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="smtp_tls_cipherlist">smtp_tls_cipherlist</a>
(default: empty)</DT><DD>

 Obsolete Postfix < 2.3 control for the Postfix SMTP client TLS
cipher list. As this feature applies to all TLS security levels, it is easy
to create interoperability problems by choosing a non-default cipher
list. Do not use a non-default TLS cipher list on hosts that deliver email
to the public Internet: you will be unable to send email to servers that
only support the ciphers you exclude. Using a restricted cipher list
may be more appropriate for an internal MTA, where one can exert some
control over the TLS software and settings of the peer servers. 

 Note: do not use "" quotes around the parameter value. 

 This feature is available in Postfix version 2.2. It is not used with
Postfix 2.3 and later; use <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> instead. 

</DD>

<DT><a name="smtp_tls_ciphers">smtp_tls_ciphers</a>
(default: medium)</DT><DD>

 The minimum TLS cipher grade that the Postfix SMTP client
will use with opportunistic TLS encryption. Cipher types listed in
<a href="postconf.5.html#smtp_tls_exclude_ciphers">smtp_tls_exclude_ciphers</a> are excluded from the base definition of
the selected cipher grade. The default value is "medium" for
Postfix releases after the middle of 2015, "export" for older
releases. 

 When TLS is mandatory the cipher grade is chosen via the
<a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> configuration parameter, see there for syntax
details. See <a href="postconf.5.html#smtp_tls_policy_maps">smtp_tls_policy_maps</a> for information on how to configure
ciphers on a per-destination basis. 

 This feature is available in Postfix 2.6 and later. With earlier Postfix
releases only the <a href="postconf.5.html#smtp_tls_mandatory_ciphers">smtp_tls_mandatory_ciphers</a> parameter is implemented,
and opportunistic TLS always uses "export" or better (i.e. all) ciphers. 

</DD>

<DT><a name="smtp_tls_connection_reuse">smtp_tls_connection_reuse</a>
(default: no)</DT><DD>

 Try to make multiple deliveries per TLS-encrypted connection.
This uses the <a href="tlsproxy.8.html">tlsproxy(8)</a> service to encrypt an SMTP connection,
uses the <a href="scache.8.html">scache(8)</a> service to save that connection, and relies on
hints from the <a href="qmgr.8.html">qmgr(8)</a> daemon. 

 See "<a href="TLS_README.html#client_tls_reuse">Client-side
TLS connection reuse</a>" for background details. 

 This feature is available in Postfix 3.4 and later. 

</DD>

<DT><a name="smtp_tls_dane_insecure_mx_policy">smtp_tls_dane_insecure_mx_policy</a>
(default: dane)</DT><DD>

 The TLS policy for MX hosts with "secure" TLSA records when the
nexthop destination security level is dane, but the MX
record was found via an "insecure" MX lookup. The choices are:


<dl>
<dt>may</dt>
<dd> The TLSA records will be ignored and TLS will be optional. If
the MX host does not appear to support STARTTLS, or the STARTTLS
handshake fails, mail may be sent in the clear. </dd>
<dt>encrypt</dt>
<dd> The TLSA records will signal a requirement to use TLS. While
TLS encryption will be required, authentication will not be performed.
</dd>
<dt>dane</dt>
<dd>The TLSA records will be used just as with "secure" MX records.
TLS encryption will be required, and, if at least one of the TLSA
records is "usable", authentication will be required. When
authentication succeeds, it will be logged only as "Trusted", not
"Verified", because the MX host name could have been forged. </dd>
</dl>

 The default setting is "dane" as of Postfix versions 3.6.17,
3.7.13, 3.8.8, 3.9.2, and 3.10.0. With earlier versions the default
was mistakenly dependent on the <a href="postconf.5.html#smtp_tls_security_level">smtp_tls_security_level</a> setting.


 Though with "insecure" MX records an active attacker can
compromise SMTP transport security by returning forged MX records,
such attacks are "tamper-evident" since any forged MX hostnames
will be recorded in the mail logs. Attackers who place a high value
on staying hidden may be deterred from forging MX records. 


This feature is available in Postfix 3.1 and later. The may
policy is backwards-compatible with earlier Postfix versions.


</DD>

<DT><a name="smtp_tls_dcert_file">smtp_tls_dcert_file</a>
(default: empty)</DT><DD>

 File with the Postfix SMTP client DSA certificate in PEM format.
This file may also contain the Postfix SMTP client private DSA key.
The DSA algorithm is obsolete and should not be used. 

 See the discussion under <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> for more details.


 Example: 

<pre>
<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a> = /etc/postfix/client-dsa.pem
</pre>

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_tls_dkey_file">smtp_tls_dkey_file</a>
(default: $<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>)</DT><DD>

 File with the Postfix SMTP client DSA private key in PEM format.
This file may be combined with the Postfix SMTP client DSA certificate
file specified with $<a href="postconf.5.html#smtp_tls_dcert_file">smtp_tls_dcert_file</a>. The DSA algorithm is obsolete
and should not be used. 

 The private key must be accessible without a pass-phrase, i.e. it
must not be encrypted. File permissions should grant read-only
access to the system superuser account ("root"), and no access
to anyone else. 

 This feature is available in Postfix 2.2 and later. 

</DD>

<DT><a name="smtp_tls_eccert_file">smtp_tls_eccert_file</a>
(default: empty)</DT><DD>

 File with the Postfix SMTP client ECDSA certificate in PEM format.
This file may also contain the Postfix SMTP client ECDSA private key.
With Postfix ≥ 3.4 the preferred way to configure client keys and
certificates is via the "<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>" parameter. 

 See the discussion under <a href="postconf.5.html#smtp_tls_cert_file">smtp_tls_cert_file</a> for more details.


 Example: 

<pre>
<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a> = /etc/postfix/ecdsa-ccert.pem
</pre>

 This feature is available in Postfix 2.6 and later, when Postfix is
compiled and linked with OpenSSL 1.0.0 or later. 

</DD>

<DT><a name="smtp_tls_eckey_file">smtp_tls_eckey_file</a>
(default: $<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a>)</DT><DD>

 File with the Postfix SMTP client ECDSA private key in PEM format.
This file may be combined with the Postfix SMTP client ECDSA certificate
file specified with $<a href="postconf.5.html#smtp_tls_eccert_file">smtp_tls_eccert_file</a>. With Postfix ≥ 3.4 the
preferred way to configure client keys and certificates is via the
"<a href="postconf.5.html#smtp_tls_chain_files">smtp_tls_chain_files</a>" parameter. 

 The private key must be accessible without a pass-phrase, i.e. it
must not be encrypted. File permissions should grant read-only
access to the system superuser account ("root"), and no access
to anyone else. 

 This feature is available in Postfix 2.6 and later, when Postfix is
compiled and linked with OpenSSL 1.0.0 or later. 

</DD>

<DT><a name="smtp_tls_enable_rpk">smtp_tls_enable_rpk</a>
(default: no)</DT><DD>

 Request that remote SMTP servers send an <a href="https://tools.ietf.org/html/rfc7250">RFC7250</a> raw public key
instead of an X.509 certificate. This feature and the enable_rpk
policy attribute are ignored when there is no raw public key support
in the local TLS implementation. 

<ul>

<li> At the "may", "encrypt" and "fingerprint" security levels,
with parameter setting "<a href="postconf.5.html#smtp_tls_enable_rpk">smtp_tls_enable_rpk</a> = yes" or with "enable_rpk
--> --------------------

--> maximum size reached

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