POSTCONF(5) POSTCONF(5)
NAME
postconf(1,5) - Postfix configuration parameters
SYNOPSIS
postconf(1,5) parameter ...
postconf(1,5) -e "parameter=value" ...
DESCRIPTION
The Postfix main.cf configuration file(1,n) specifies a small subset of all
the parameters that control the operation of the Postfix mail(1,8) system.
Parameters not specified in(1,8) main.cf are left at their default values.
The general format of the main.cf file(1,n) is as follows:
Each logical line has the form "parameter = value". Whitespace
around the "=" is ignored, as is whitespace at the end of a log-
ical line.
Empty lines and whitespace-only lines are ignored, as are lines
whose first non-whitespace character is a `#'.
A logical line starts with non-whitespace text. A line that
starts with whitespace continues a logical line.
A parameter value may refer to other parameters.
The expressions "$name", "${name}" or "$(name)" are
recursively replaced by the value of the named(5,8) parameter.
The expression "${name?value}" expands to "value" when
"$name" is non-empty. This form is supported with Postfix
version(1,3,5) 2.2 and later.
The expression "${name:value}" expands to "value" when
"$name" is empty. This form is supported with Postfix
version(1,3,5) 2.2 and later.
When the same parameter is defined multiple times, only the last
instance is remembered.
Otherwise, the order of main.cf parameter definitions does not
matter.
The remainder of this document is a description of all Postfix configu-
ration parameters. Default values are shown after the parameter name in(1,8)
parentheses, and can be looked up with the "postconf(1,5) -d" command.
Note: this is not an invitation to make changes to Postfix configura-
tion parameters. Unnecessary changes can impair the operation of the
mail(1,8) system.
2bounce_notice_recipient (default: postmaster)
The recipient of undeliverable mail(1,8) that cannot be returned to the
sender. This feature is enabled with the notify_classes parameter.
access_map_reject_code (default: 554)
The numerical Postfix SMTP server response code when a client is
rejected by an access(2,5)(5) map restriction.
Do not change this unless you have a complete understanding of RFC 821.
address_verify_default_transport (default: $default_transport)
Overrides the default_transport parameter setting for address verifica-
tion probes.
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_local_transport (default: $local_transport)
Overrides the local_transport parameter setting for address verifica-
tion probes.
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_map (default: empty)
Optional lookup table for persistent address verification status stor-
age. The table is maintained by the verify(1,8)(8) service, and is opened
before the process releases privileges.
By default, the information is kept in(1,8) volatile memory, and is lost
after "postfix reload" or "postfix stop".
Specify a location in(1,8) a file(1,n) system that will not fill up. If the data-
base becomes corrupted, the world comes to an end. To recover delete
the file(1,n) and do "postfix reload".
Examples:
address_verify_map = hash:/etc/postfix/verify(1,8)
address_verify_map = btree:/etc/postfix/verify(1,8)
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_negative_cache (default: yes)
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(1,8) Postfix 2.1 and later.
address_verify_negative_expire_time (default: 3d)
The time(1,2,n) after which a failed probe expires from the address verifica-
tion cache.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_negative_refresh_time (default: 3h)
The time(1,2,n) after which a failed address verification probe needs to be
refreshed.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_poll_count (default: 3)
How many times to query the verify(1,8)(8) service for the completion of an
address verification request in(1,8) progress.
The default poll count is 3.
Specify 1 to implement a crude form of greylisting, that is, always
defer the first delivery request for a never seen before address.
Example:
address_verify_poll_count = 1
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_poll_delay (default: 3s)
The delay between queries for the completion of an address verification
request in(1,8) progress.
The default polling delay is 3 seconds.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_positive_expire_time (default: 31d)
The time(1,2,n) after which a successful probe expires from the address veri-
fication cache.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_positive_refresh_time (default: 7d)
The time(1,2,n) after which a successful address verification probe needs to
be refreshed. The address verification status is not updated when the
probe fails (optimistic caching).
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_relay_transport (default: $relay_transport)
Overrides the relay_transport parameter setting for address verifica-
tion probes.
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_relayhost (default: $relayhost)
Overrides the relayhost parameter setting for address verification
probes.
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_sender (default: postmaster)
The sender address to use in(1,8) address verification probes. To avoid
problems with address probes that are sent in(1,8) response to address
probes, the Postfix SMTP server excludes the probe sender address from
all SMTPD access(2,5) blocks.
Specify an empty value (address_verify_sender =) or <> if(3,n) you want to
use the null sender address. Beware, some sites reject mail(1,8) from <>,
even though RFCs require that such addresses be accepted.
Examples:
address_verify_sender = <>
address_verify_sender = postmaster@my.domain
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_service_name (default: verify(1,8))
The name of the verify(1,8)(8) 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.
address_verify_transport_maps (default: $transport_maps)
Overrides the transport_maps parameter setting for address verification
probes.
This feature is available in(1,8) Postfix 2.1 and later.
address_verify_virtual_transport (default: $virtual_transport)
Overrides the virtual_transport parameter setting for address verifica-
tion probes.
This feature is available in(1,8) Postfix 2.1 and later.
alias_database (default: see postconf(1,5) -d output)
The alias databases for local(8) delivery that are updated with
"newaliases" or with "sendmail(1,8) -bi".
This is a separate configuration parameter because not all the tables
specified with $alias_maps have to be local files.
Examples:
alias_database = hash:/etc/aliases
alias_database = hash:/etc/mail(1,8)/aliases
alias_maps (default: see postconf(1,5) -d output)
The alias databases that are used for local(8) delivery. See aliases(5)
for syntax details.
The default list is system dependent. On systems with NIS, the default
is to search the local alias database, then the NIS alias database.
If you change the alias database, run "postalias /etc/aliases" (or
wherever your system stores the mail(1,8) alias file(1,n)), or simply run
"newaliases" to build the necessary DBM or DB file.
The local(8) delivery agent disallows regular expression substitution
of $1 etc. in(1,8) alias_maps, because that would open(2,3,n) a security hole.
The local(8) delivery agent will silently ignore requests to use the
proxymap(8) server within alias_maps. Instead it will open(2,3,n) the table
directly. Before Postfix version(1,3,5) 2.2, the local(8) delivery agent will
terminate with a fatal error.
Examples:
alias_maps = hash:/etc/aliases, nis:mail.aliases
alias_maps = hash:/etc/aliases
allow_mail_to_commands (default: alias, forward)
Restrict local(8) mail(1,8) delivery to external commands. The default is
to disallow delivery to "|command" in(1,8) :include: files (see aliases(5)
for the text that defines this terminology).
Specify zero or more of: alias, forward or include, in(1,8) order to allow
commands in(1,8) aliases(5), .forward files or in(1,8) :include: files, respec-
tively.
Example:
allow_mail_to_commands = alias,forward,include
allow_mail_to_files (default: alias, forward)
Restrict local(8) mail(1,8) delivery to external files. The default is to
disallow "/file(1,n)/name" destinations in(1,8) :include: files (see aliases(5)
for the text that defines this terminology).
Specify zero or more of: alias, forward or include, in(1,8) order to allow
"/file(1,n)/name" destinations in(1,8) aliases(5), .forward files and in(1,8)
:include: files, respectively.
Example:
allow_mail_to_files = alias,forward,include
allow_min_user (default: no)
Allow a 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 ter-
minator into the command line, this is difficult to enforce consis-
tently and globally.
allow_percent_hack (default: yes)
Enable the rewriting of the form "user%domain" to "user@domain". This
is enabled by default.
Note: with Postfix version(1,3,5) 2.2, message header address rewriting hap-
pens only when one of the following conditions is true:
The message is received with the Postfix sendmail(1,8)(1) command,
The message is received from a network client that matches
$local_header_rewrite_clients,
The message is received from the network, and the
remote_header_rewrite_domain parameter specifies a non-empty
value.
To get the behavior before Postfix 2.2, specify "local_header_re-
write_clients = static:all".
Example:
allow_percent_hack = no
allow_untrusted_routing (default: no)
Forward mail(1,8) with sender-specified routing (user[@%!]remote[@%!]site)
from untrusted clients to destinations matching $relay_domains.
By default, this feature is turned off. This closes a nasty open(2,3,n) relay
loophole where a backup MX host(1,5) can be tricked into forwarding junk
mail(1,8) to a primary MX host(1,5) which then spams it out to the world.
This parameter also controls if(3,n) non-local addresses with sender-speci-
fied routing can match Postfix access(2,5) tables. By default, such
addresses cannot match Postfix access(2,5) tables, because the address is
ambiguous.
alternate_config_directories (default: empty)
A list of non-default Postfix configuration directories that may be
specified with "-c config_directory" on the command line, or via the
MAIL_CONFIG environment parameter.
This list must be specified in(1,8) the default Postfix configuration direc-
tory, and is used by set-gid Postfix commands such as postqueue(1) and
postdrop(1).
always_bcc (default: empty)
Optional address that receives a "blind carbon copy" of each message
that is received by the Postfix mail(1,8) system.
Note: if(3,n) mail(1,8) to the BCC address bounces it will be returned to the
sender.
Note: automatic BCC recipients are produced only for new mail. To
avoid mailer loops, automatic BCC recipients are not generated for mail(1,8)
that Postfix forwards internally, nor for mail(1,8) that Postfix generates
itself.
anvil_rate_time_unit (default: 60s)
The time(1,2,n) unit over which client connection rates and other rates are
calculated.
This feature is implemented by the anvil(8) service which is not part
of the stable Postfix 2.1 release.
The default interval is relatively short. Because of the high frequency
of updates, the anvil(8) server uses volatile memory only. Thus, infor-
mation is lost whenever the process terminates.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
anvil_status_update_time (default: 600s)
How frequently the anvil(8) connection and rate limiting server logs
peak usage information.
This feature is available in(1,8) Postfix 2.2 and later.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
append_at_myorigin (default: yes)
With locally submitted mail(1,8), append the string(3,n) "@$myorigin" to mail(1,8)
addresses without domain information. With remotely submitted mail(1,8),
append the string(3,n) "@$remote_header_rewrite_domain" 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(1,3,5) 2.2, message header address rewriting hap-
pens only when one of the following conditions is true:
The message is received with the Postfix sendmail(1,8)(1) command,
The message is received from a network client that matches
$local_header_rewrite_clients,
The message is received from the network, and the
remote_header_rewrite_domain parameter specifies a non-empty
value.
To get the behavior before Postfix 2.2, specify "local_header_re-
write_clients = static:all".
append_dot_mydomain (default: yes)
With locally submitted mail(1,8), append the string(3,n) ".$mydomain" to
addresses that have no ".domain" information. With remotely submitted
mail(1,8), append the string(3,n) ".$remote_header_rewrite_domain" instead.
Note 1: this feature is enabled by default. If disabled, users(1,5) will not
be able to send(2,n) mail(1,8) to "user@partialdomainname" but will have to spec-
ify full domain names instead.
Note 2: with Postfix version(1,3,5) 2.2, message header address rewriting hap-
pens only when one of the following conditions is true:
The message is received with the Postfix sendmail(1,8)(1) command,
The message is received from a network client that matches
$local_header_rewrite_clients,
The message is received from the network, and the
remote_header_rewrite_domain parameter specifies a non-empty
value.
To get the behavior before Postfix 2.2, specify "local_header_re-
write_clients = static:all".
application_event_drain_time (default: 100s)
How long the postkick(1) command waits for a request to enter the
server's input buffer before giving up.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
This feature is available in(1,8) Postfix 2.1 and later.
authorized_flush_users (default: static:anyone)
List of users(1,5) who are authorized to flush(8,n) the queue.
By default, all users(1,5) are allowed to flush(8,n) the queue. Access is always
granted if(3,n) the invoking user is the super-user or the $mail_owner user.
Otherwise, the real UID of the process is looked up in(1,8) the system pass-
word file(1,n), and access(2,5) is granted only if(3,n) the corresponding login(1,3,5) name
is on the access(2,5) list. The username "unknown" is used for processes
whose real UID is not found in(1,8) the password file.
Specify a list of user names, "/file(1,n)/name" or "type:table" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. Specify "!name" to
exclude a name from the list. A "/file(1,n)/name" pattern is replaced by its
contents; a "type:table" 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.
This feature is available in(1,8) Postfix 2.2 and later.
authorized_mailq_users (default: static:anyone)
List of users(1,5) who are authorized to view the queue.
By default, all users(1,5) are allowed to view the queue. Access is always
granted if(3,n) the invoking user is the super-user or the $mail_owner user.
Otherwise, the real UID of the process is looked up in(1,8) the system pass-
word file(1,n), and access(2,5) is granted only if(3,n) the corresponding login(1,3,5) name
is on the access(2,5) list. The username "unknown" is used for processes
whose real UID is not found in(1,8) the password file.
Specify a list of user names, "/file(1,n)/name" or "type:table" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. Specify "!name" to
exclude a name from the list. A "/file(1,n)/name" pattern is replaced by its
contents; a "type:table" 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.
This feature is available in(1,8) Postfix 2.2 and later.
authorized_submit_users (default: static:anyone)
List of users(1,5) who are authorized to submit mail(1,8) with the sendmail(1,8)(1)
command (and with the privileged postdrop(1) helper command).
By default, all users(1,5) are allowed to submit mail. Otherwise, the real
UID of the process is looked up in(1,8) the system password file(1,n), and access(2,5)
is granted only if(3,n) the corresponding login(1,3,5) name is on the access(2,5) list.
The username "unknown" is used for processes whose real UID is not
found in(1,8) the password file. To deny mail(1,8) submission access(2,5) to all users(1,5)
specify an empty list.
Specify a list of user names, "/file(1,n)/name" or "type:table" patterns,
separated by commas and/or whitespace. The list is matched left to
right, and the search stops on the first match. Specify "!name" to
exclude a name from the list. A "/file(1,n)/name" pattern is replaced by its
contents; a "type:table" 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.
This feature is available in(1,8) Postfix 2.2 and later.
authorized_verp_clients (default: $mynetworks)
What SMTP clients are allowed to specify the XVERP command. This com-
mand requests that mail(1,8) be delivered one recipient at a time(1,2,n) with a per
recipient return address.
By default, only trusted clients are allowed to specify XVERP.
This parameter was introduced with Postfix version(1,3,5) 1.1. Postfix ver-
sion(1,3,5) 2.1 renamed this parameter to smtpd_authorized_verp_clients 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(1,8) the network part
of a host(1,5) address. You can also specify hostnames or .domain names (the
initial dot causes the domain to match any name below it),
"/file(1,n)/name" or "type:table" patterns. A "/file(1,n)/name" pattern is
replaced by its contents; a "type:table" lookup table is matched when a
table entry matches a lookup string(3,n) (the lookup result is ignored).
Continue long lines by starting the next line with whitespace.
Note: IP version(1,3,5) 6 address information must be specified inside
<tt>[]</tt> in(1,8) the authorized_verp_clients value, and in(1,8) files speci-
fied with "/file(1,n)/name". IP version(1,3,5) 6 addresses contain the ":" charac-
ter, and would otherwise be confused with a "type:table" pattern.
backwards_bounce_logfile_compatibility (default: yes)
Produce additional bounce(8) logfile records that can be read(2,n,1 builtins) by Post-
fix versions before 2.0. The current and more extensible "name = value"
format is needed in(1,8) order to implement more sophisticated functional-
ity.
This feature is available in(1,8) Postfix 2.1 and later.
berkeley_db_create_buffer_size (default: 16777216)
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(1,8) Postfix 2.0 and later.
berkeley_db_read_buffer_size (default: 131072)
The per-table I/O buffer size for programs that read(2,n,1 builtins) Berkeley DB hash
or btree tables. Specify a byte count.
This feature is available in(1,8) Postfix 2.0 and later.
best_mx_transport (default: empty)
Where the Postfix SMTP client should deliver mail(1,8) when it detects a
"mail(1,8) loops back to myself" error(8,n) condition. This happens when the
local MTA is the best SMTP mail(1,8) exchanger for a destination not listed
in(1,8) $mydestination, $inet_interfaces, $proxy_interfaces, $vir-
tual_alias_domains, or $virtual_mailbox_domains. By default, the Post-
fix SMTP client returns such mail(1,8) as undeliverable.
Specify, for example, "best_mx_transport = local" to pass the mail(1,8) from
the SMTP client to the local(8) delivery agent. You can specify any
message delivery "transport" or "transport:nexthop" that is defined in(1,8)
the master.cf file. See the transport(5) 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 local(8) delivery agent is doing its work. It
is more efficient (for Postfix) to list all hosted domains in(1,8) a table
or database.
biff (default: yes)
Whether or not to use the local biff service. This service sends "new
mail(1,8)" notifications to users(1,5) who have requested new mail(1,8) notification
with the UNIX command "biff y".
For compatibility reasons this feature is on by default. On systems
with lots of interactive users(1,5), the biff service can be a performance
drain. Specify "biff = no" in(1,8) main.cf to disable.
body_checks (default: empty)
Optional lookup tables for content inspection as specified in(1,8) the
body_checks(5) manual page.
Note: with Postfix versions before 2.0, these rules inspect all content
after the primary message headers.
body_checks_size_limit (default: 51200)
How much text in(1,8) a message body segment (or attachment, if(3,n) you prefer
to use that term(5,7)) is subjected to body_checks inspection. The amount
of text is limited to avoid scanning huge attachments.
This feature is available in(1,8) Postfix 2.0 and later.
bounce_notice_recipient (default: postmaster)
The recipient of postmaster notifications with the message headers of
mail(1,8) that Postfix did not deliver and of SMTP conversation transcripts
of mail(1,8) that Postfix did not receive. This feature is enabled with the
notify_classes parameter.
bounce_queue_lifetime (default: 5d)
The maximal time(1,2,n) a bounce message is queued before it is considered
undeliverable. By default, this is the same as the queue(1,3) life time(1,2,n) for
regular mail.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is d (days).
Specify 0 when mail(1,8) delivery should be tried only once.
This feature is available in(1,8) Postfix 2.1 and later.
bounce_service_name (default: bounce)
The name of the bounce(8) service. This service maintains a record of
failed delivery attempts and generates non-delivery notifications.
This feature is available in(1,8) Postfix 2.0 and later.
bounce_size_limit (default: 50000)
The maximal amount of original message text that is sent in(1,8) a non-
delivery notification. Specify a byte count. If you increase this
limit, then you should increase the mime_nesting_limit value propor-
tionally.
broken_sasl_auth_clients (default: no)
Enable inter-operability with SMTP clients that implement an obsolete
version(1,3,5) of the AUTH command (RFC 2554). Examples of such clients are
MicroSoft Outlook Express version(1,3,5) 4 and MicroSoft Exchange version(1,3,5) 5.0.
Specify "broken_sasl_auth_clients = yes" to have Postfix advertise AUTH
support in(1,8) a non-standard way.
canonical_classes (default: envelope_sender, envelope_recipient,
header_sender, header_recipient)
What addresses are subject to canonical_maps address mapping. By
default, canonical_maps 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(1,8) Postfix 2.2 and later.
canonical_maps (default: empty)
Optional address mapping lookup tables for message headers and
envelopes. The mapping is applied to both sender and recipient
addresses, in(1,8) both envelopes and in(1,8) headers, as controlled with the
canonical_classes parameter. This is typically used to clean up dirty
addresses from legacy mail(1,8) systems, or to replace login(1,3,5) names by First-
name.Lastname. The table format and lookups are documented in(1,8) canoni-
cal(5). For an overview of Postfix address manipulations see the
ADDRESS_REWRITING_README document.
If you use this feature, run "postmap /etc/postfix/canonical" to build
the necessary DBM or DB file(1,n) after every change. The changes will
become visible after a minute or so. Use "postfix reload" to eliminate
the delay.
Note: with Postfix version(1,3,5) 2.2, message header address mapping happens
only when message header address rewriting is enabled:
The message is received with the Postfix sendmail(1,8)(1) command,
The message is received from a network client that matches
$local_header_rewrite_clients,
The message is received from the network, and the
remote_header_rewrite_domain parameter specifies a non-empty
value.
To get the behavior before Postfix 2.2, specify "local_header_re-
write_clients = static:all".
Examples:
canonical_maps = dbm:/etc/postfix/canonical
canonical_maps = hash:/etc/postfix/canonical
cleanup_service_name (default: cleanup)
The name of the cleanup(8) service. This service rewrites addresses
into the standard form, and performs canonical(5) address mapping and
virtual(5,8)(5) aliasing.
This feature is available in(1,8) Postfix 2.0 and later.
command_directory (default: see postconf(1,5) -d output)
The location of all postfix administrative commands.
command_execution_directory (default: empty)
The local(8) delivery agent working directory for delivery to external
command. Failure to change directory causes the delivery to be
deferred.
The following $name expansions are done on command_execution_directory
before the directory is changed. Expansion happens in(1,8) the context of
the delivery request. The result of $name expansion is filtered with
the character set(7,n,1 builtins) that is specified with the execution_directory_expan-
sion_filter parameter.
$user The recipient's username.
$shell The recipient's login(1,3,5) shell pathname.
$home The recipient's home directory.
$recipient
The full recipient address.
$extension
The optional recipient address extension.
$domain
The recipient domain.
$local The entire recipient localpart.
$recipient_delimiter
The system-wide recipient address extension delimiter.
${name?value}
Expands to value when $name is non-empty.
${name:value}
Expands to value when $name is empty.
Instead of $name you can also specify ${name} or $(name).
This feature is available in(1,8) Postfix 2.2 and later.
command_expansion_filter (default: see postconf(1,5) -d output)
Restrict the characters that the local(8) delivery agent allows in(1,8)
$name expansions of $mailbox_command. Characters outside the allowed
set(7,n,1 builtins) are replaced by underscores.
command_time_limit (default: 1000s)
Time limit for delivery to external commands. This limit is used by the
local(8) delivery agent, and is the default time(1,2,n) limit for delivery by
the pipe(2,8)(8) delivery agent.
Note: if(3,n) you set(7,n,1 builtins) this time(1,2,n) limit to a large value you must update(7,n) the
global ipc_timeout parameter as well.
config_directory (default: see postconf(1,5) -d output)
The default location of the Postfix main.cf and master.cf configuration
files. This can be overruled via the following mechanisms:
The MAIL_CONFIG environment variable (daemon processes and com-
mands).
The "-c" command-line option (commands only).
With Postfix command that run with set-gid privileges, a config_direc-
tory override requires either root privileges, or it requires that the
directory is listed with the alternate_config_directories parameter in(1,8)
the default main.cf file.
connection_cache_service (default: scache)
The name of the scache(8) connection cache service. This service main-
tains a limited pool of cached sessions.
connection_cache_status_update_time (default: 600s)
How frequently the scache(8) server logs usage statistics with connec-
tion cache hit and miss rates for logical destinations and for physical
endpoints.
connection_cache_ttl_limit (default: 2s)
The maximal time-to-live value that the scache(8) 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 $max_idle.
content_filter (default: empty)
The name of a mail(1,8) delivery transport that filters mail(1,8) after it is
queued.
This parameter uses the same syntax as the right-hand side of a Postfix
transport(5) table. This setting has a lower precedence than a content
filter(1,3x,3x curs_util) that is specified with an access(2,5)(5) table or in(1,8) a
header_checks(5) or body_checks(5) table.
daemon_directory (default: see postconf(1,5) -d output)
The directory with Postfix support programs and daemon programs. These
should not be invoked directly by humans. The directory must be owned
by root.
daemon_timeout (default: 18000s)
How much time(1,2,n) a Postfix daemon process may take to handle a request
before it is terminated by a built-in watchdog(5,8) timer.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
debug_peer_level (default: 2)
The increment in(1,8) verbose logging level when a remote client or server
matches a pattern in(1,8) the debug_peer_list parameter.
debug_peer_list (default: empty)
Optional list of remote client or server hostname or network address
patterns that cause the verbose logging level to increase by the amount
specified in(1,8) $debug_peer_level.
Specify domain names, network/netmask patterns, "/file(1,n)/name" patterns
or "type:table" lookup tables. The right-hand side result from
"type:table" lookups is ignored.
Pattern matching of domain names is controlled by the par-
ent_domain_matches_subdomains parameter.
Examples:
debug_peer_list = 127.0.0.1
debug_peer_list = some.domain
debugger_command (default: empty)
The external command to execute when a Postfix daemon program is
invoked with the -D option.
Use "command .. & sleep(1,3) 5" so that the debugger can attach before the
process marches on. If you use an X-based debugger, be sure to set(7,n,1 builtins) up
your XAUTHORITY environment variable before starting Postfix.
Example:
debugger_command =
PATH=/usr/bin:/usr/X11R6/bin
xxgdb $daemon_directory/$process_name $process_id & sleep(1,3) 5
default_database_type (default: see postconf(1,5) -d output)
The default database type for use in(1,8) newaliases(1), postalias(1) and
postmap(1) commands. On many UNIX systems the default type is either
dbm or hash. The default setting is frozen when the Postfix system is
built.
Examples:
default_database_type = hash
default_database_type = dbm
default_delivery_slot_cost (default: 5)
How often the Postfix queue(1,3) 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 is the counter incremented -
it happens after each default_delivery_slot_cost 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(3,n) you
want to maximize the message throughput rate. Although there is no max-
imum, 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,
their delivery can take somewhere between (cost+1/cost) and
(cost/cost-1) times more than if(3,n) 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(1,8) the worst case.
Examples:
default_delivery_slot_cost = 0
default_delivery_slot_cost = 2
default_delivery_slot_discount (default: 50)
The default value for transport-specific _delivery_slot_discount set-
tings.
This parameter speeds up the moment when a message preemption can hap-
pen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when transport_deliv-
ery_slot_discount percent of the required amount plus transport_deliv-
ery_slot_loan still remains to be accumulated. Note that the full
amount will still have to be accumulated before another preemption can
take place later.
default_delivery_slot_loan (default: 3)
The default value for transport-specific _delivery_slot_loan settings.
This parameter speeds up the moment when a message preemption can hap-
pen. Instead of waiting until the full amount of delivery slots
required is available, the preemption can happen when transport_deliv-
ery_slot_discount percent of the required amount plus transport_deliv-
ery_slot_loan still remains to be accumulated. Note that the full
amount will still have to be accumulated before another preemption can
take place later.
default_destination_concurrency_limit (default: 20)
The default maximal number of parallel deliveries to the same destina-
tion. This is the default limit for delivery via the lmtp(8), pipe(2,8)(8),
smtp(8) and virtual(5,8)(8) delivery agents.
default_destination_recipient_limit (default: 50)
The default maximal number of recipients per message delivery. This is
the default limit for delivery via the lmtp(8), pipe(2,8)(8), smtp(8) and
virtual(5,8)(8) delivery agents.
Setting this parameter to a value of 1 changes the meaning of the cor-
responding per-destination concurrency limit from concurrency per
domain into concurrency per recipient.
default_extra_recipient_limit (default: 1000)
The default value for the extra per-transport limit imposed on the num-
ber of in-memory recipients. This extra recipient space is reserved
for the cases when the Postfix queue(1,3) manager's scheduler preempts one
message with another and suddenly needs some extra recipients slots for
the chosen message in(1,8) order to avoid performance degradation.
default_minimum_delivery_slots (default: 3)
How many recipients a message must have in(1,8) order to invoke the Postfix
queue(1,3) 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.
default_privs (default: nobody)
The default rights used by the local(8) delivery agent for delivery to
external file(1,n) or command. These rights are used when delivery is
requested from an aliases(5) file(1,n) that is owned by root, or when deliv-
ery is done on behalf of root. DO NOT SPECIFY A PRIVILEGED USER OR THE
POSTFIX OWNER.
default_process_limit (default: 100)
The default maximal number of Postfix child processes that provide a
given service. This limit can be overruled for specific services in(1,8) the
master.cf file.
default_rbl_reply (default: see postconf(1,5) -d output)
The default SMTP server response template for a request that is
rejected by an RBL-based restriction. This template can be overruled by
specific entries in(1,8) the optional rbl_reply_maps lookup table.
This feature is available in(1,8) Postfix 2.0 and later.
The template is subject to exactly one level of $name substitution:
$client
The client hostname and IP address, formatted as name[address].
$client_address
The client IP address.
$client_name
The client hostname or "unknown".
$helo_name
The hostname given in(1,8) HELO or EHLO command or empty string.
$rbl_class
The blacklisted entity type: Client host(1,5), Helo command, Sender
address, or Recipient address.
$rbl_code
The numerical SMTP response code, as specified with the
maps_rbl_reject_code configuration parameter.
$rbl_domain
The RBL domain where $rbl_what is blacklisted.
$rbl_reason
The reason why $rbl_what is blacklisted, or an empty string.
$rbl_what
The entity that is blacklisted (an IP address, a hostname, a
domain name, or an email address whose domain was blacklisted).
$recipient
The recipient address or <> in(1,8) case of the null address.
$recipient_domain
The recipient domain or empty string.
$recipient_name
The recipient address localpart or <> in(1,8) case of null address.
$sender
The sender address or <> in(1,8) case of the null address.
$sender_domain
The sender domain or empty string.
$sender_name
The sender address localpart or <> in(1,8) case of the null address.
${name?text}
Expands to `text' if(3,n) $name is not empty.
${name:text}
Expands to `text' if(3,n) $name is empty.
Instead of $name you can also specify ${name} or $(name).
default_recipient_limit (default: 10000)
The default per-transport upper limit on the number of in-memory recip-
ients. These limits take priority over the global qmgr_message_recipi-
ent_limit after the message has been assigned to the respective trans-
ports. See also default_extra_recipient_limit and qmgr_message_recipi-
ent_minimum.
default_transport (default: smtp)
The default mail(1,8) delivery transport for domains that do not match
$mydestination, $inet_interfaces, $proxy_interfaces, $vir-
tual_alias_domains, $virtual_mailbox_domains, or $relay_domains. This
information can be overruled with the transport(5) table.
Specify a string(3,n) of the form transport:nexthop, where transport is the
name of a mail(1,8) delivery transport defined in(1,8) master.cf. The :nexthop
part is optional. For more details see the transport(5) manual page.
Example:
default_transport = uucp:relayhostname
default_verp_delimiters (default: +=)
The two default VERP delimiter characters. These are used when no
explicit delimiters are specified with the SMTP XVERP command or with
the "sendmail(1,8) -V" command-line option. Specify characters that are
allowed by the verp_delimiter_filter setting.
This feature is available in(1,8) Postfix 1.1 and later.
defer_code (default: 450)
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 RFC 821.
defer_service_name (default: defer)
The name of the defer(8) service. This service maintains a record of
failed delivery attempts and generates non-delivery notifications.
This feature is available in(1,8) Postfix 2.0 and later.
defer_transports (default: empty)
The names of message delivery transports that should not be delivered
to unless someone issues "sendmail(1,8) -q" or equivalent. Specify zero or
more names of mail(1,8) delivery transports names that appear in(1,8) the first
field of master.cf.
Example:
defer_transports = smtp
delay_notice_recipient (default: postmaster)
The recipient of postmaster notifications with the message headers of
mail(1,8) that cannot be delivered within $delay_warning_time time(1,2,n) units.
This feature is enabled with the delay_warning_time parameter.
delay_warning_time (default: 0h)
The time(1,2,n) after which the sender receives the message headers of mail(1,8)
that is still queued.
To enable this feature, specify a non-zero integral value.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is h (hours).
deliver_lock_attempts (default: 20)
The maximal number of attempts to acquire an exclusive lock on a mail-
box file(1,n) or bounce(8) logfile.
deliver_lock_delay (default: 1s)
The time(1,2,n) between attempts to acquire an exclusive lock on a mailbox
file(1,n) or bounce(8) logfile.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
disable_dns_lookups (default: no)
Disable DNS lookups in(1,8) the Postfix SMTP and LMTP clients. When dis-
abled, hosts are looked up with the gethostbyname() system library rou-
tine which normally also looks in(1,8) /etc/hosts.
DNS lookups are enabled by default.
disable_mime_input_processing (default: no)
Turn off MIME processing while receiving mail. This means that no spe-
cial 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(1,8) Postfix 2.0 and later.
Mime input processing is enabled by default, and is needed in(1,8) order to
recognize MIME headers in(1,8) message content.
disable_mime_output_conversion (default: no)
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(1,8) Postfix 2.0 and later.
disable_verp_bounces (default: no)
Disable sending one bounce report per recipient.
The default, one per recipient, is what ezmlm needs.
This feature is available in(1,8) Postfix 1.1 and later.
disable_vrfy_command (default: no)
Disable the SMTP VRFY command. This stops some techniques used to har-
vest email addresses.
Example:
disable_vrfy_command = no
dont_remove (default: 0)
Don't remove queue(1,3) files and save them to the "saved" mail(1,8) queue. This
is a debugging aid. To inspect the envelope information and content of
a Postfix queue(1,3) file(1,n), use the postcat(1) command.
double_bounce_sender (default: double-bounce)
The sender address of postmaster notifications that are generated by
the mail(1,8) system. All mail(1,8) to this address is silently discarded, in(1,8)
order to terminate mail(1,8) bounce loops.
duplicate_filter_limit (default: 1000)
The maximal number of addresses remembered by the address duplicate
filter(1,3x,3x curs_util) for aliases(5) or virtual(5,8)(5) alias expansion, or for showq(8)
queue(1,3) displays.
empty_address_recipient (default: MAILER-DAEMON)
The recipient of mail(1,8) addressed to the null address. Postfix does not
accept(2,8) such addresses in(1,8) SMTP commands, but they may still be created
locally as the result of configuration or software error.
enable_errors_to (default: no)
Report mail(1,8) delivery errors to the address specified with the non-stan-
dard Errors-To: message header, instead of the envelope sender address
(this feature is removed with Postfix 2.2, is turned off by default
with Postfix 2.1, and is always turned on with older Postfix versions).
enable_original_recipient (default: yes)
Enable support for the X-Original-To message header. This header is
needed for multi-recipient mailboxes.
When this parameter is set(7,n,1 builtins) to yes, the cleanup(8) daemon performs
duplicate elimination on distinct pairs of (original recipient, rewrit-
ten recipient), and generates non-empty original recipient queue(1,3) file(1,n)
records.
When this parameter is set(7,n,1 builtins) to no, the cleanup(8) daemon performs dupli-
cate elimination on the rewritten recipient address only, and generates
empty original recipient queue(1,3) file(1,n) records.
This feature is available in(1,8) Postfix 2.1 and later. With Postfix 2.0,
support for the X-Original-To message header is always turned on. Post-
fix versions before 2.0 have no support for the X-Original-To message
header.
error_notice_recipient (default: postmaster)
The recipient of postmaster notifications about mail(1,8) delivery problems
that are caused by policy, resource, software or protocol errors.
These notifications are enabled with the notify_classes parameter.
error_service_name (default: error(8,n))
The name of the error(8,n)(8) pseudo delivery agent. This service always
returns mail(1,8) as undeliverable.
This feature is available in(1,8) Postfix 2.0 and later.
execution_directory_expansion_filter (default: see postconf(1,5) -d output)
Restrict the characters that the local(8) delivery agent allows in(1,8)
$name expansions of $command_execution_directory. Characters outside
the allowed set(7,n,1 builtins) are replaced by underscores.
This feature is available in(1,8) Postfix 2.2 and later.
expand_owner_alias (default: no)
When delivering to an alias "aliasname" that has an "owner-aliasname"
companion alias, set(7,n,1 builtins) 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.
export_environment (default: see postconf(1,5) -d output)
The list of environment variables that a Postfix process will export to
non-Postfix processes. The TZ variable is needed for sane time(1,2,n) keeping
on System-V-ish systems.
Specify a list of names and/or name=value pairs, separated by white-
space or comma. The name=value form is supported with Postfix 2.1 and
later.
Example:
export_environment = TZ PATH=/bin:/usr/bin
extract_recipient_limit (default: 10240)
The maximal number of recipient addresses that Postfix will extract
from message headers when mail(1,8) is submitted with "sendmail(1,8) -t".
This feature was removed in(1,8) Postfix 2.1.
fallback_relay (default: empty)
Optional list of relay hosts for SMTP destinations that can't be found
or that are unreachable.
By default, mail(1,8) is returned to the sender when a destination is not
found, and delivery is deferred if(3,n) a destination is unreachable.
The fallback relays must be SMTP destinations. Specify a domain, host(1,5),
host:port, [host(1,5)]:port, [address] or [address]:port; the form [host(1,5)]
turns off MX lookups. If you specify multiple SMTP destinations, Post-
fix will try them in(1,8) the specified order.
Note: do not use the fallback_relay feature when relaying mail(1,8) for a
backup or primary MX domain. Mail would loop between the Postfix MX
host(1,5) and the fallback_relay host(1,5) when the final destination is unavail-
able.
In main.cf specify "relay_transport = relay",
In master.cf specify "-o fallback_relay =" (i.e., empty) at the
end of the <tt>relay</tt> entry.
In transport maps, specify "relay:nexthop..." as the right-hand
side for backup or primary MX domain entries.
These are default settings in(1,8) Postfix version(1,3,5) 2.2 and later.
fallback_transport (default: empty)
Optional message delivery transport that the local(8) delivery agent
should use for names that are not found in(1,8) the aliases(5) database or
in(1,8) the UNIX passwd(1,5) database.
fast_flush_domains (default: $relay_domains)
Optional list of destinations that are eligible for per-destination
logfiles with mail(1,8) that is queued to those destinations.
By default, Postfix maintains "fast flush(8,n)" logfiles only for destina-
tions that the Postfix SMTP server is willing to relay to (i.e. the
default is: "fast_flush_domains = $relay_domains"; see the
relay_domains parameter in(1,8) the postconf(1,5)(5) manual).
Specify a list of hosts or domains, "/file(1,n)/name" patterns or "type:ta-
ble" lookup tables, separated by commas and/or whitespace. Continue
long lines by starting the next line with whitespace. A "/file(1,n)/name"
pattern is replaced by its contents; a "type:table" lookup table is
matched when the domain or its parent domain appears as lookup key.
Specify "fast_flush_domains =" (i.e., empty) to disable the feature
altogether.
fast_flush_purge_time (default: 7d)
The time(1,2,n) after which an empty per-destination "fast flush(8,n)" logfile is
deleted.
You can specify the time(1,2,n) as a number, or as a number followed by a let-
ter that indicates the time(1,2,n) unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks. The default time(1,2,n) unit is days.
fast_flush_refresh_time (default: 12h)
The time(1,2,n) after which a non-empty but unread per-destination "fast
flush(8,n)" logfile needs to be refreshed. The contents of a logfile are
refreshed by requesting delivery of all messages listed in(1,8) the logfile.
You can specify the time(1,2,n) as a number, or as a number followed by a let-
ter that indicates the time(1,2,n) unit: s=seconds, m=minutes, h=hours,
d=days, w=weeks. The default time(1,2,n) unit is hours.
fault_injection_code (default: 0)
Force specific internal tests to fail, to test the handling of errors
that are difficult to reproduce otherwise.
flush_service_name (default: flush(8,n))
The name of the flush(8,n)(8) service. This service maintains per-destina-
tion logfiles with the queue(1,3) file(1,n) names of mail(1,8) that is queued for
those destinations.
This feature is available in(1,8) Postfix 2.0 and later.
fork_attempts (default: 5)
The maximal number of attempts to fork() a child process.
fork_delay (default: 1s)
The delay between attempts to fork() a child process.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
forward_expansion_filter (default: see postconf(1,5) -d output)
Restrict the characters that the local(8) delivery agent allows in(1,8)
$name expansions of $forward_path. Characters outside the allowed set(7,n,1 builtins)
are replaced by underscores.
forward_path (default: see postconf(1,5) -d output)
The local(8) delivery agent search list for finding a .forward file(1,n)
with user-specified delivery methods. The first file(1,n) that is found is
used.
The following $name expansions are done on forward_path before the
search actually happens. The result of $name expansion is filtered with
the character set(7,n,1 builtins) that is specified with the forward_expansion_filter
parameter.
$user The recipient's username.
$shell The recipient's login(1,3,5) shell pathname.
$home The recipient's home directory.
$recipient
The full recipient address.
$extension
The optional recipient address extension.
$domain
The recipient domain.
$local The entire recipient localpart.
$recipient_delimiter
The system-wide recipient address extension delimiter.
${name?value}
Expands to value when $name is non-empty.
${name:value}
Expands to value when $name is empty.
Instead of $name you can also specify ${name} or $(name).
Examples:
forward_path = /var/forward/$user
forward_path =
/var/forward/$user/.forward$recipient_delimiter$extension,
/var/forward/$user/.forward
hash_queue_depth (default: 1)
The number of subdirectory levels for queue(1,3) directories listed with the
hash_queue_names parameter.
After changing the hash_queue_names or hash_queue_depth parameter, exe-
cute the command "postfix reload".
hash_queue_names (default: deferred, defer)
The names of queue(1,3) directories that are split(1,n) across multiple subdirec-
tory levels.
Before Postfix version(1,3,5) 2.2, the default list of hashed queues was sig-
nificantly larger. Claims about improvements in(1,8) file(1,n) system technology
suggest that hashing of the incoming and active queues is no longer
needed. Fewer hashed directories speed up the time(1,2,n) needed to restart
Postfix.
After changing the hash_queue_names or hash_queue_depth parameter, exe-
cute the command "postfix reload".
header_address_token_limit (default: 10240)
The maximal number of address tokens are allowed in(1,8) an address message
header. Information that exceeds the limit is discarded. The limit is
enforced by the cleanup(8) server.
header_checks (default: empty)
Optional lookup tables for content inspection of primary non-MIME mes-
sage headers, as specified in(1,8) the header_checks(5) manual page.
header_size_limit (default: 102400)
The maximal amount of memory in(1,8) bytes for storing a message header. If
a header is larger, the excess is discarded. The limit is enforced by
the cleanup(8) server.
helpful_warnings (default: yes)
Log warnings about problematic configuration settings, and provide
helpful suggestions.
This feature is available in(1,8) Postfix 2.0 and later.
home_mailbox (default: empty)
Optional pathname of a mailbox file(1,n) relative to a local(8) user's home
directory.
Specify a pathname ending "/" for qmail-style delivery.
The precedence of local(8) delivery features from high to low is:
aliases, .forward files, mailbox_transport, mailbox_command_maps, mail-
box_command, home_mailbox, mail_spool_directory, fallback_transport and
luser_relay.
Examples:
home_mailbox = Mailbox
home_mailbox = Maildir/
hopcount_limit (default: 50)
The maximal number of Received: message headers that is allowed in(1,8) the
primary message headers. A message that exceeds the limit is bounced,
in(1,8) order to stop a mailer loop.
html_directory (default: see postconf(1,5) -d output)
The location of Postfix HTML files that describe how to build, config-
ure or operate a specific Postfix subsystem or feature.
ignore_mx_lookup_error (default: no)
Ignore DNS MX lookups that produce no response. By default, the Post-
fix SMTP client defers delivery and tries again after some delay. This
behavior is required by the SMTP standard.
Specify "ignore_mx_lookup_error = yes" to force a DNS A record lookup
instead. This violates the SMTP standard and can result in(1,8) mis-delivery
of mail.
import_environment (default: see postconf(1,5) -d output)
The list of environment parameters that a Postfix process will import
from a non-Postfix parent process. Examples of relevant parameters:
TZ Needed for sane time(1,2,n) keeping on most System-V-ish systems.
DISPLAY
Needed for debugging Postfix daemons with an X-windows debugger.
XAUTHORITY
Needed for debugging Postfix daemons with an X-windows debugger.
MAIL_CONFIG
Needed to make "postfix -c" work.
Specify a list of names and/or name=value pairs, separated by white-
space or comma. The name=value form is supported with Postfix 2.1 and
later.
in_flow_delay (default: 1s)
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 SMTP server process limit, "in_flow_delay = 1s"
limits the mail(1,8) 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.
inet_interfaces (default: all)
The network interface addresses that this mail(1,8) system receives mail(1,8) on.
Specify "all" to receive mail(1,8) on all network interfaces (default), and
"loopback-only" to receive mail(1,8) on loopback network interfaces only
(Postfix 2.2 and later). The parameter also controls delivery of mail(1,8)
to <tt>user@[ip.address]</tt>.
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 recommended here.
When inet_interfaces specifies just one IPv4 and/or IPv6 address that
is not a loopback address, the Postfix SMTP client will use this
address as the IP source address for outbound mail. Support for IPv6 is
available in(1,8) Postfix version(1,3,5) 2.2 and later.
On a multi-homed firewall with separate Postfix instances listening on
the "inside" and "outside" interfaces, this can prevent each instance
from being able to reach servers on the "other side" of the firewall.
Setting smtp_bind_address to 0.0.0.0 avoids the potential problem for
IPv4, and setting smtp_bind_address6 to :: solves the problem for IPv6.
A better solution for multi-homed firewalls is to leave inet_interfaces
at the default value and instead use explicit IP addresses in(1,8) the mas-
ter.cf SMTP server definitions. This preserves the 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 $inet_interfaces to a
single IPv4 and/or IPV6 address is primarily useful with virtual(5,8) host-
ing of domains on secondary IP addresses, when each IP address serves a
different domain (and has a different $myhostname setting).
See also the proxy_interfaces parameter, for network addresses that are
forwarded to Postfix by way of a proxy or address translator.
Examples:
inet_interfaces = all (DEFAULT)
inet_interfaces = loopback-only (Postfix 2.2 and later)
inet_interfaces = 127.0.0.1
inet_interfaces = 127.0.0.1, [::1] (Postfix 2.2 and later)
inet_interfaces = 192.168.1.2, 127.0.0.1
inet_protocols (default: ipv4)
The Internet protocols Postfix will attempt to use when making or
accepting connections. Specify one or more of "ipv4" or "ipv6", sepa-
rated by whitespace or commas. The form "all" is equivalent to "ipv4,
ipv6" or "ipv4", depending on whether the operating system implements
IPv6.
This feature is available in(1,8) Postfix version(1,3,5) 2.2 and later.
Note: you MUST stop and start Postfix after changing this parameter.
On systems that pre-date IPV6_V6ONLY support (RFC 3493), an IPv6 server
will also accept(2,8) IPv4 connections, even when IPv4 is turned off with
the inet_protocols parameter. On systems with IPV6_V6ONLY support,
Postfix will use separate server sockets for IPv6 and IPv4, and each
will accept(2,8) only connections for the corresponding protocol.
When IPv4 support is enabled via the inet_protocols parameter, Postfix
will to DNS type A record lookups, 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 (RFC
3493).
When IPv6 support is enabled via the inet_protocols parameter, Postfix
will do DNS type AAAA record lookups.
When both IPv4 and IPv6 support are enabled, the Postfix SMTP client
will attempt to connect via IPv6 before attempting to use IPv4.
Examples:
inet_protocols = ipv4 (DEFAULT)
inet_protocols = all
inet_protocols = ipv6
inet_protocols = ipv4, ipv6
initial_destination_concurrency (default: 5)
The initial per-destination concurrency level for parallel delivery to
the same destination. This limit applies to delivery via smtp(8), and
via the pipe(2,8)(8) and virtual(5,8)(8) delivery agents.
Warning: with concurrency of 1, one bad message can be enough to block
all mail(1,8) to a site.
invalid_hostname_reject_code (default: 501)
The numerical Postfix SMTP server response code when the client HELO or
EHLO command parameter is rejected by the reject_invalid_hostname
restriction.
Do not change this unless you have a complete understanding of RFC 821.
ipc_idle (default: 100s)
The time(1,2,n) after which a client closes an idle internal communication
channel. The purpose is to allow servers to terminate voluntarily
after they become idle. This is used, for example, by the address
resolving and rewriting clients.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
ipc_timeout (default: 3600s)
The time(1,2,n) limit for sending or receiving information over an internal
communication channel. The purpose is to break out of deadlock situa-
tions. If the time(1,2,n) limit is exceeded the software aborts with a fatal
error.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
ipc_ttl (default: 1000s)
The time(1,2,n) after which a client closes an active internal communication
channel. The purpose is to allow servers to terminate voluntarily
after reaching their client limit. This is used, for example, by the
address resolving and rewriting clients.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
This feature is available in(1,8) Postfix 2.1 and later.
line_length_limit (default: 2048)
Upon input, long lines are chopped up into pieces of at most this
length; upon delivery, long lines are reconstructed.
lmtp_cache_connection (default: yes)
Keep Postfix LMTP client connections open(2,3,n) for up to $max_idle seconds.
When the LMTP client receives a request for the same connection the
connection is reused.
The effectiveness of cached connections will be determined by the num-
ber of LMTP servers in(1,8) use, and the concurrency limit specified for the
LMTP client. Cached connections are closed under any of the following
conditions:
The LMTP client idle time(1,2,n) limit is reached. This limit is spec-
ified with the Postfix max_idle configuration parameter.
A delivery request specifies a different destination than the
one currently cached.
The per-process limit on the number of delivery requests is
reached. This limit is specified with the Postfix max_use con-
figuration parameter.
Upon the onset of another delivery request, the LMTP server
associated with the current session does not respond to the RSET
command.
Most of these limitations will be removed after Postfix implements a
connection cache that is shared among multiple LMTP client programs.
lmtp_connect_timeout (default: 0s)
The LMTP client time(1,2,n) limit for completing a TCP connection, or zero
(use the operating system built-in time(1,2,n) limit). When no connection can
be made within the deadline, the LMTP client tries the next address on
the mail(1,8) exchanger list.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
Example:
lmtp_connect_timeout = 30s
lmtp_data_done_timeout (default: 600s)
The LMTP client time(1,2,n) limit for sending the LMTP ".", and for receiving
the server response. When no response is received within the deadline,
a warning is logged that the mail(1,8) may be delivered multiple times.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_data_init_timeout (default: 120s)
The LMTP client time(1,2,n) limit for sending the LMTP DATA command, and for
receiving the server response.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_data_xfer_timeout (default: 180s)
The LMTP client time(1,2,n) limit for sending the LMTP message content. When
the connection stalls for more than $lmtp_data_xfer_timeout the LMTP
client terminates the transfer.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_destination_concurrency_limit (default: $default_destination_concur-
rency_limit)
The maximal number of parallel deliveries to the same destination via
the lmtp message delivery transport. This limit is enforced by the
queue(1,3) manager. The message delivery transport name is the first field
in(1,8) the entry in(1,8) the master.cf file.
lmtp_destination_recipient_limit (default: $default_destination_recipi-
ent_limit)
The maximal number of recipients per delivery via the lmtp message
delivery transport. This limit is enforced by the queue(1,3) manager. The
message delivery transport name is the first field in(1,8) the entry in(1,8) the
master.cf file.
Setting this parameter to a value of 1 changes the meaning of lmtp_des-
tination_concurrency_limit from concurrency per domain into concurrency
per recipient.
lmtp_lhlo_timeout (default: 300s)
The LMTP client time(1,2,n) limit for receiving the LMTP greeting banner.
When the server drops the connection without sending a greeting banner,
or when it sends no greeting banner within the deadline, the LMTP
client tries the next address on the mail(1,8) exchanger list.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_mail_timeout (default: 300s)
The LMTP client time(1,2,n) limit for sending the MAIL FROM command, and for
receiving the server response.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_quit_timeout (default: 300s)
The LMTP client time(1,2,n) limit for sending the QUIT command, and for
receiving the server response.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_rcpt_timeout (default: 300s)
The LMTP client time(1,2,n) limit for sending the RCPT TO command, and for
receiving the server response.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_rset_timeout (default: 20s)
The LMTP client time(1,2,n) limit for sending the RSET command, and for
receiving the server response. The LMTP client sends RSET in(1,8) order to
finish a recipient address probe, or to verify(1,8) that a cached connection
is still alive.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
lmtp_sasl_auth_enable (default: no)
Enable SASL authentication in(1,8) the Postfix LMTP client.
lmtp_sasl_password_maps (default: empty)
Optional LMTP client lookup tables with one username:password entry per
host(1,5) or domain. If a remote host(1,5) or domain has no username:password
entry, then the Postfix LMTP client will not attempt to authenticate to
the remote host.
lmtp_sasl_security_options (default: noplaintext, noanonymous)
What authentication mechanisms the Postfix LMTP client is allowed to
use. The list of available authentication mechanisms is system depen-
dent.
noplaintext
Disallow authentication methods that use plaintext passwords.
noactive
Disallow authentication methods that are vulnerable to non-dic-
tionary active attacks.
nodictionary
Disallow authentication methods that are vulnerable to passive
dictionary attack.
noanonymous
Disallow anonymous logins.
Example:
lmtp_sasl_security_options = noplaintext
lmtp_send_xforward_command (default: no)
Send an XFORWARD command to the LMTP server when the LMTP LHLO server
response announces XFORWARD support. This allows an lmtp(8) delivery
agent, used for content filter(1,3x,3x curs_util) message injection, to forward the name,
address, protocol and HELO name of the original client to the content
filter(1,3x,3x curs_util) and downstream queuing LMTP server. Before you change the value
to yes, it is best to make sure that your content filter(1,3x,3x curs_util) supports this
command.
This feature is available in(1,8) Postfix 2.1 and later.
lmtp_skip_quit_response (default: no)
Wait for the response to the LMTP QUIT command.
lmtp_tcp_port (default: 24)
The default TCP port that the Postfix LMTP client connects to.
lmtp_xforward_timeout (default: 300s)
The LMTP client time(1,2,n) limit for sending the XFORWARD command, and for
receiving the server response.
In case of problems the client does NOT try the next address on the
mail(1,8) exchanger list.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
The default time(1,2,n) unit is s (seconds).
This feature is available in(1,8) Postfix 2.1 and later.
local_command_shell (default: empty)
Optional shell program for local(8) delivery to non-Postfix command.
By default, non-Postfix commands are executed directly; commands are
given to given to /bin/sh only when they contain shell meta characters
or shell built-in commands.
"sendmail(1,8)'s restricted shell" (smrsh) is what most people will use in(1,8)
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:
local_command_shell = /some/where/smrsh -c
local_destination_concurrency_limit (default: 2)
The maximal number of parallel deliveries via the local mail(1,8) delivery
transport to the same recipient (when "local_destination_recipi-
ent_limit = 1") or the maximal number of parallel deliveries to the
same local domain (when "local_destination_recipient_limit > 1"). This
limit is enforced by the queue(1,3) manager. The message delivery transport
name is the first field in(1,8) the entry in(1,8) the master.cf file.
A low limit of 2 is recommended, just in(1,8) case someone has an expensive
shell command in(1,8) a .forward file(1,n) or in(1,8) an alias (e.g., a mailing list
manager). You don't want to run lots of those at the same time.
local_destination_recipient_limit (default: 1)
The maximal number of recipients per message delivery via the local
mail(1,8) delivery transport. This limit is enforced by the queue(1,3) manager.
The message delivery transport name is the first field in(1,8) the entry in(1,8)
the master.cf file.
Setting this parameter to a value > 1 changes the meaning of local_des-
tination_concurrency_limit from concurrency per recipient into concur-
rency per domain.
local_header_rewrite_clients (default: permit_inet_interfaces)
Rewrite message header addresses in(1,8) mail(1,8) from these clients and update(7,n)
incomplete addresses with the domain name in(1,8) $myorigin or $mydomain;
either don't rewrite message headers from other clients at all, or re-
write(1,2) message headers and update(7,n) incomplete addresses with the domain
specified in(1,8) the remote_header_rewrite_domain parameter.
See the append_at_myorigin and append_dot_mydomain parameters for
details of how domain names are appended to incomplete addresses.
Specify a list of zero or more of the following:
permit_inet_interfaces
Append the domain name in(1,8) $myorigin or $mydomain when the client
IP address matches $inet_interfaces. This is enabled by default.
permit_mynetworks
Append the domain name in(1,8) $myorigin or $mydomain when the client
IP address matches any network or network address listed in(1,8)
$mynetworks. This setting will not prevent remote mail(1,8) header
address rewriting when mail(1,8) from a remote client is forwarded by
a neighboring system.
permit_sasl_authenticated
Append the domain name in(1,8) $myorigin or $mydomain when the client
is successfully authenticated via the RFC 2554 (AUTH) protocol.
permit_tls_clientcerts
Append the domain name in(1,8) $myorigin or $mydomain when the client
TLS certificate is successfully verified, and the client cer-
tificate fingerprint is listed in(1,8) $relay_clientcerts.
permit_tls_all_clientcerts
Append the domain name in(1,8) $myorigin or $mydomain when the client
TLS certificate is successfully verified, regardless of whether
it is listed on the server, and regardless of the certifying
authority.
check_address_map type:table
type:table
Append the domain name in(1,8) $myorigin or $mydomain when the client
IP address matches the specified lookup table. The lookup
result is ignored, and no subnet lookup is done. This is suit-
able for, e.g., pop-before-smtp lookup tables.
Examples:
The Postfix < 2.2 backwards compatible setting: always rewrite message
headers, and always append my own domain to incomplete header
addresses.
local_header_rewrite_clients = static:all
The purist (and default) setting: rewrite headers only in(1,8) mail(1,8) from
Postfix sendmail(1,8) and in(1,8) SMTP mail(1,8) from this machine.
local_header_rewrite_clients = permit_inet_interfaces
The intermediate setting: rewrite header addresses and append $myorigin
or $mydomain information only with mail(1,8) from Postfix sendmail(1,8), from
local clients, or from authorized SMTP clients.
Note: this setting will not prevent remote mail(1,8) header address rewrit-
ing when mail(1,8) from a remote client is forwarded by a neighboring sys-
tem.
local_header_rewrite_clients = permit_mynetworks,
permit_sasl_authenticated permit_tls_clientcerts
check_address_map hash:/etc/postfix/pop-before-smtp
local_recipient_maps (default: proxy:unix:passwd.byname $alias_maps)
Lookup tables with all names or addresses of local recipients: a recip-
ient address is local when its domain matches $mydestination,
$inet_interfaces or $proxy_interfaces. Specify @domain as a wild-card
for domains that do not have a valid recipient list. Technically,
tables listed with $local_recipient_maps are used as lists: Postfix
needs to know only if(3,n) a lookup string(3,n) is found or not, but it does not
use the result from table lookup.
If this parameter is non-empty (the default), then the Postfix SMTP
server will reject mail(1,8) for unknown local users.
To turn off local recipient checking in(1,8) the Postfix SMTP server, spec-
ify "local_recipient_maps =" (i.e. empty).
The default setting assumes that you use the default Postfix local
delivery agent for local delivery. You need to update(7,n) the local_recipi-
ent_maps setting if:
You redefine the local delivery agent in(1,8) master.cf.
You redefine the "local_transport" setting in(1,8) main.cf.
You use the "luser_relay", "mailbox_transport", or "fall-
back_transport" feature of the Postfix local(8) delivery agent.
Details are described in(1,8) the LOCAL_RECIPIENT_README file.
Beware: if(3,n) the Postfix SMTP server runs chrooted, you need to access(2,5)
the passwd(1,5) file(1,n) via the proxymap(8) service, in(1,8) order to overcome
chroot(1,2) access(2,5) restrictions. The alternative, maintaining a copy of the
system password file(1,n) in(1,8) the chroot(1,2) jail is not practical.
Examples:
local_recipient_maps =
local_transport (default: local:$myhostname)
The default mail(1,8) delivery transport for domains that match $mydestina-
tion, $inet_interfaces or $proxy_interfaces. This information can be
overruled with the transport(5) table.
By default, local mail(1,8) is delivered to the transport called "local",
which is just the name of a service that is defined the master.cf file.
Specify a string(3,n) of the form transport:nexthop, where transport is the
name of a mail(1,8) delivery transport defined in(1,8) master.cf. The :nexthop
part is optional. For more details see the transport(5) manual page.
Beware: if(3,n) you override the default local delivery agent then you need
to review the LOCAL_RECIPIENT_README document, otherwise the SMTP
server may reject mail(1,8) for local recipients.
luser_relay (default: empty)
Optional catch-all destination for unknown local(8) recipients. By
default, mail(1,8) for unknown recipients in(1,8) domains that match $mydestina-
tion, $inet_interfaces or $proxy_interfaces is returned as undeliver-
able.
The following $name expansions are done on luser_relay:
$domain
The recipient domain.
$extension
The recipient address extension.
$home The recipient's home directory.
$local The entire recipient address localpart.
$recipient
The full recipient address.
$recipient_delimiter
The system-wide recipient address extension delimiter.
$shell The recipient's login(1,3,5) shell.
$user The recipient username.
${name?value}
Expands to value when $name has a non-empty value.
${name:value}
Expands to value when $name has an empty value.
Instead of $name you can also specify ${name} or $(name)