Postfix Configuration Parameters Postfix Configuration Parameters The Postfix main.cf 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 main.cf file is as follows:
Each logical line is in the form "parameter = value". Whitespace around the "=" is ignored, as is whitespace at the end of a logical 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 "$(name)" are recursively replaced by the value of the named parameter.
The expression "${name?value}" expands to "value" when "$name" is non-empty. This form is supported with Postfix version 2.2 and later.
The expression "${name:value}" expands to "value" when "$name" is empty. This form is supported with Postfix version 2.2 and later.
Specify "$$" to produce a single "$" character.
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 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.
The recipient of undeliverable mail that cannot be returned to the sender. This feature is enabled with the notify_classes parameter.
The numerical Postfix SMTP server response code for an access(5) map "defer" action, including "defer_if_permit" or "defer_if_reject". Prior to Postfix 2.6, the response is hard-coded as "450".
Do not change this unless you have a complete understanding of RFC 5321.
This feature is available in Postfix 2.6 and later.
The numerical Postfix SMTP server response code for an access(5) map "reject" action.
Do not change this unless you have a complete understanding of RFC 5321.
The amount of time between verify(8) 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 verify(8) 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 $max_idle seconds.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in Postfix 2.7.
Overrides the default_transport parameter setting for address verification probes.
This feature is available in Postfix 2.1 and later.
Overrides the local_transport parameter setting for address verification probes.
This feature is available in Postfix 2.1 and later.
Lookup table for persistent address verification status storage. The table is maintained by the verify(8) 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 data_directory. As a migration aid, an attempt to open the file under a non-Postfix directory is redirected to the Postfix-owned data_directory, and a warning is logged.
Examples:
address_verify_map = hash:/var/lib/postfix/verify address_verify_map = btree:/var/lib/postfix/verify
This feature is available in Postfix 2.1 and later.
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.
The time after which a failed probe expires from the address verification cache.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in Postfix 2.1 and later.
The time 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 Postfix 2.1 and later.
How many times to query the verify(8) service for the completion of an address verification request in progress.
By default, the Postfix SMTP server polls the verify(8) 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 verify(8) 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:
# Postfix ≤ 2.6 default address_verify_poll_count = 3 # Poor man's greylisting address_verify_poll_count = 1
This feature is available in Postfix 2.1 and later.
The delay between queries for the completion of an address verification request in 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 Postfix 2.1 and later.
The time after which a successful probe expires from the address verification cache.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in Postfix 2.1 and later.
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).
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in Postfix 2.1 and later.
Overrides the relay_transport parameter setting for address verification probes.
This feature is available in Postfix 2.1 and later.
Overrides the relayhost parameter setting for address verification probes. This information can be overruled with the transport(5) table.
This feature is available in Postfix 2.1 and later.
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 (address_verify_sender =) 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:
address_verify_sender = <> address_verify_sender = postmaster@my.domain
This feature is available in Postfix 2.1 and later.
Overrides the sender_dependent_default_transport_maps parameter setting for address verification probes.
This feature is available in Postfix 2.7 and later.
Overrides the sender_dependent_relayhost_maps parameter setting for address verification probes.
This feature is available in Postfix 2.3 and later.
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 address_verify_sender parameter. This feature is ignored when the probe sender addresses is the null sender, i.e. the address_verify_sender 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 (an integral value plus an optional one-letter suffix that specifies the time unit). 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. Time units are: s (seconds), m (minutes), h (hours), d (days), w (weeks).
This feature is available in Postfix 2.9 and later.
The name of the verify(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.
Overrides the transport_maps parameter setting for address verification probes.
This feature is available in Postfix 2.1 and later.
Overrides the virtual_transport parameter setting for address verification probes.
This feature is available in Postfix 2.1 and later.
The alias databases for local(8) delivery that are updated with "newaliases" or with "sendmail -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/aliases
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 alias file), 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 alias_maps, because that would open 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 the table directly. Before Postfix version 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
Restrict local(8) mail delivery to external commands. The default is to disallow delivery to "|command" in :include: files (see aliases(5) for the text that defines this terminology).
Specify zero or more of: alias, forward or include, in order to allow commands in aliases(5), .forward files or in :include: files, respectively.
Example:
allow_mail_to_commands = alias,forward,include
Restrict local(8) mail delivery to external files. The default is to disallow "/file/name" destinations in :include: files (see aliases(5) for the text that defines this terminology).
Specify zero or more of: alias, forward or include, in order to allow "/file/name" destinations in aliases(5), .forward files and in :include: files, respectively.
Example:
allow_mail_to_files = alias,forward,include
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 trivial-rewrite(8). With earlier versions this feature was implemented by qmgr(8) and was limited to recipient addresses only.
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:
To get the behavior before Postfix version 2.2, specify "local_header_rewrite_clients = static:all".
Example:
allow_percent_hack = no
Forward mail 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 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.
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 the default Postfix configuration directory, and is used by set-gid Postfix commands such as postqueue(1) and postdrop(1).
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 local_header_rewrite_clients parameter setting. Earlier Postfix versions always add these headers; this may break DKIM signatures that cover non-existent headers.
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 RFC 3461.
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.
The time unit over which client connection rates and other rates are calculated.
This feature is implemented by the anvil(8) 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 anvil(8) server uses volatile memory only. Thus, information is lost whenever the process terminates.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks). The default time unit is s (seconds).
How frequently the anvil(8) connection and rate limiting server logs peak usage information.
This feature is available in Postfix 2.2 and later.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks). The default time unit is s (seconds).
With locally submitted mail, append the string "@$myorigin" to mail addresses without domain information. With remotely submitted mail, append the string "@$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 2.2, message header address rewriting happens only when one of the following conditions is true:
To get the behavior before Postfix version 2.2, specify "local_header_rewrite_clients = static:all".
With locally submitted mail, append the string ".$mydomain" to addresses that have no ".domain" information. With remotely submitted mail, append the string ".$remote_header_rewrite_domain" instead.
Note 1: this feature is enabled by default. If disabled, 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:
To get the behavior before Postfix version 2.2, specify "local_header_rewrite_clients = static:all".
How long the postkick(1) command waits for a request to enter the Postfix daemon process input buffer before giving up.
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.
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 $mail_owner 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 "type:table" 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 "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. 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.
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 $mail_owner 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 "type:table" 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 "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. 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.
List of users who are authorized to submit mail with the sendmail(1) command (and with the privileged postdrop(1) 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 "type:table" 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 "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. 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:
authorized_submit_users = !www, static:all
This feature is available in Postfix 2.2 and later.
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 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 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 "type:table" patterns. A "/file/name" pattern is replaced by its contents; a "type:table" 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 [] in the authorized_verp_clients value, and in files specified with "/file/name". IP version 6 addresses contain the ":" character, and would otherwise be confused with a "type:table" pattern.
Produce additional bounce(8) 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.
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.
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.
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 $mydestination, $inet_interfaces, $proxy_interfaces, $virtual_alias_domains, or $virtual_mailbox_domains. By default, the Postfix SMTP client returns such mail as undeliverable.
Specify, for example, "best_mx_transport = local" to pass the mail from the Postfix SMTP client to the local(8) delivery agent. You can specify any message delivery "transport" or "transport:nexthop" that is defined in 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 a table or database.
Whether or not to use the local biff service. This service sends "new mail" notifications to users who have requested new mail notification with the UNIX command "biff y".
For compatibility reasons this feature is on by default. On systems with lots of interactive users, the biff service can be a performance drain. Specify "biff = no" in main.cf to disable.
Optional lookup tables for content inspection as specified in the body_checks(5) manual page.
Note: with Postfix versions before 2.0, these rules inspect all content after the primary message headers.
How much text in a message body segment (or attachment, if you prefer to use that term) is subjected to body_checks inspection. The amount of text is limited to avoid scanning huge attachments.
This feature is available in Postfix 2.0 and later.
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 notify_classes parameter.
Consider a bounce message as undeliverable, when delivery fails with a temporary error, and the time in the queue has reached the bounce_queue_lifetime limit. By default, this limit is the same as for regular mail.
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.
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 Postfix 2.0 and later.
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:
If you increase this limit, then you should increase the mime_nesting_limit value proportionally.
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.
Pathname of a configuration file with bounce message templates. These override the built-in templates of delivery status notification (DSN) messages for undeliverable mail, for delayed mail, successful delivery, or delivery verification. The bounce(5) 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.
Enable inter-operability with remote SMTP clients that implement an obsolete version of the AUTH command (RFC 4954). Examples of such clients are MicroSoft Outlook Express version 4 and MicroSoft Exchange version 5.0.
Specify "broken_sasl_auth_clients = yes" to have Postfix advertise AUTH support in a non-standard way.
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 Postfix 2.2 and later.
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 canonical_classes 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 canonical(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 after every change. The changes will become visible after a minute or so. Use "postfix reload" to eliminate the delay.
Note: with Postfix version 2.2, message header address mapping happens only when message header address rewriting is enabled:
To get the behavior before Postfix version 2.2, specify "local_header_rewrite_clients = static:all".
Examples:
canonical_maps = dbm:/etc/postfix/canonical canonical_maps = hash:/etc/postfix/canonical
The name of the cleanup(8) service. This service rewrites addresses into the standard form, and performs canonical(5) address mapping and virtual(5) aliasing.
This feature is available in Postfix 2.0 and later.
The location of all postfix administrative commands.
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 the context of the delivery request. The result of $name expansion is filtered with the character set that is specified with the execution_directory_expansion_filter parameter.
Instead of $name you can also specify ${name} or $(name).
This feature is available in Postfix 2.2 and later.
Restrict the characters that the local(8) delivery agent allows in $name expansions of $mailbox_command and $command_execution_directory. Characters outside the allowed set are replaced by underscores.
Time limit for delivery to external commands. This limit is used by the local(8) delivery agent, and is the default time limit for delivery by the pipe(8) delivery agent.
Note: if you set this time limit to a large value you must update the global ipc_timeout parameter as well.
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 commands).
The "-c" command-line option (commands only).
With Postfix command that run with set-gid privileges, a config_directory override requires either root privileges, or it requires that the directory is listed with the alternate_config_directories parameter in the default main.cf file.
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.
The name of the scache(8) connection cache service. This service maintains a limited pool of cached sessions.
This feature is available in Postfix 2.2 and later.
How frequently the scache(8) server logs usage statistics with connection cache hit and miss rates for logical destinations and for physical endpoints.
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.
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 master.cf; 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 FILTER_README file.
Notes:
This setting has lower precedence than a FILTER action that is specified in an access(5), header_checks(5) or body_checks(5) table.
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 $myhostname. Specify "default_filter_nexthop = $myhostname" for compatibility with Postfix 2.6 or earlier, or specify a content_filter value with an explicit next-hop destination.
Search path for Cyrus SASL application configuration files, currently used only to locate the $smtpd_sasl_path.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.
This feature is available in Postfix 2.5 and later when compiled with Cyrus SASL 2.1.22 or later.
The directory with Postfix support programs and daemon programs. These should not be invoked directly by humans. The directory must be owned by root.
How a Postfix daemon process handles errors while opening lookup tables: gradual degradation or immediate termination.
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 notify_classes 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.
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.
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.
How much time a Postfix daemon process may take to handle a request before it is terminated by a built-in watchdog timer.
Time units: s (seconds), m (minutes), h (hours), d (days), w (weeks). The default time unit is s (seconds).
The directory with Postfix-writable data files (for example: caches, pseudo-random numbers). This directory must be owned by the mail_owner account, and must not be shared with non-Postfix software.
This feature is available in Postfix 2.5 and later.
The increment in verbose logging level when a remote client or server matches a pattern in the debug_peer_list parameter.
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 $debug_peer_level.
Specify domain names, network/netmask patterns, "/file/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 parent_domain_matches_subdomains parameter.
Examples:
debug_peer_list = 127.0.0.1 debug_peer_list = example.com
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:
debugger_command =
PATH=/usr/bin:/usr/X11R6/bin
ddd $daemon_directory/$process_name $process_id & sleep 5
The default database type for use in 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
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 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 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, their 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 transport_delivery_slot_cost to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
Examples:
default_delivery_slot_cost = 0 default_delivery_slot_cost = 2
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 transport_delivery_slot_discount percent of the required amount plus transport_delivery_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.
Use transport_delivery_slot_discount to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
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 transport_delivery_slot_discount percent of the required amount plus transport_delivery_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.
Use transport_delivery_slot_loan to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
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 transport_destination_concurrency_failed_cohort_limit to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
This feature is available in Postfix 2.5. The default setting is compatible with earlier Postfix versions.
The default maximal number of parallel deliveries to the same destination. This is the default limit for delivery via the lmtp(8), pipe(8), smtp(8) and virtual(8) delivery agents. With per-destination recipient limit > 1, a destination is a domain, otherwise it is a recipient.
Use transport_destination_concurrency_limit to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
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 $default_destination_concurrency_failed_cohort_limit (or $transport_destination_concurrency_failed_cohort_limit). 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:
A pseudo-cohort is the number of deliveries equal to a destination's delivery concurrency.
Use transport_destination_concurrency_negative_feedback to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
This feature is available in Postfix 2.5. The default setting is compatible with earlier Postfix versions.
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:
A pseudo-cohort is the number of deliveries equal to a destination's delivery concurrency.
Use transport_destination_concurrency_positive_feedback to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
This feature is available in Postfix 2.5 and later.
The default amount of delay that is inserted between individual deliveries to the same destination; the resulting behavior depends on the value of the corresponding per-destination recipient limit.
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 master.cf.
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 master.cf.
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 transport_destination_rate_delay to specify a transport-specific override, where transport is the master.cf name of the message delivery transport.
NOTE: with a non-zero _destination_rate_delay, specify a transport_destination_concurrency_failed_cohort_limit 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.
The default maximal number of recipients per message delivery. This is the default limit for delivery via the lmtp(8), pipe(8), smtp(8) and virtual(8) delivery agents.
Setting this parameter to a value of 1 affects email deliveries as follows:
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 master.cf.
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 master.cf.
It changes the meaning of other corresponding per-destination settings in a similar manner, fro