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local - Postfix local mail delivery
local [generic Postfix daemon options]
The local(8) daemon updates queue files and marks recipients as finished, or it informs the queue manager that delivery should be tried again at a later time. Delivery status reports are sent to the bounce(8), defer(8) or trace(8) daemon as appropriate.
All delivery decisions are made using the bare recipient name (i.e. the address localpart), folded to lower case. See also under ADDRESS EXTENSION below for a few exceptions.
The system administrator can set up one or more system-wide sendmail-style alias databases. Users can have sendmail-style ~/.forward files. Mail for name is delivered to the alias name, to destinations in ~name/.forward, to the mailbox owned by the user name, or it is sent back as undeliverable.
The system administrator can specify a comma/space separated list of ~/.forward like files through the forward_path configuration parameter. Upon delivery, the local delivery agent tries each pathname in the list until a file is found.
Delivery via ~/..forward files is done with the privileges of the recipient. Thus, ~/.forward like files must be readable by the recipient, and their parent directory needs to have "execute" permission for the recipient.
The forward_path parameter is subject to interpolation of $user (recipient username), $home (recipient home directory), $shell (recipient shell), $recipient (complete recipient address), $extension (recipient address extension), $domain (recipient domain), $local (entire recipient address localpart) and $recipient_delimiter. The forms ${name?value} and ${name:value} expand conditionally to value when $name is (is not) defined. Characters that may have special meaning to the shell or file system are replaced by underscores. The list of acceptable characters is specified with the forward_expansion_filter configuration parameter.
An alias or ~/.forward file may list any combination of external commands, destination file names, :include: directives, or mail addresses. See aliases(5) for a precise description. Each line in a user's .forward file has the same syntax as the right-hand part of an alias.
When an address is found in its own alias expansion, delivery is made to the user instead. When a user is listed in the user's own ~/.forward file, delivery is made to the user's mailbox instead. An empty ~/.forward file means do not forward mail.
In order to prevent the mail system from using up unreasonable amounts of memory, input records read from :include: or from ~/.forward files are broken up into chunks of length line_length_limit.
While expanding aliases, ~/.forward files, and so on, the program attempts to avoid duplicate deliveries. The duplicate_filter_limit configuration parameter limits the number of remembered recipients.
For the sake of reliability, forwarded mail is re-submitted as a new message, so that each recipient has a separate on-file delivery status record.
In order to stop mail forwarding loops early, the software adds an optional Delivered-To: header with the final envelope recipient address. If mail arrives for a recipient that is already listed in a Delivered-To: header, the message is bounced.
The default per-user mailbox is a file in the UNIX mail spool directory (/var/mail/user or /var/spool/mail/user); the location can be specified with the mail_spool_directory configuration parameter. Specify a name ending in / for qmail-compatible maildir delivery.
Alternatively, the per-user mailbox can be a file in the user's home directory with a name specified via the home_mailbox configuration parameter. Specify a relative path name. Specify a name ending in / for qmail-compatible maildir delivery.
Mailbox delivery can be delegated to an external command specified with the mailbox_command_maps and mailbox_command configuration parameters. The command executes with the privileges of the recipient user (exceptions: secondary groups are not enabled; in case of delivery as root, the command executes with the privileges of default_privs).
Mailbox delivery can be delegated to alternative message transports specified in the master.cf file. The mailbox_transport_maps and mailbox_transport configuration parameters specify an optional message transport that is to be used for all local recipients, regardless of whether they are found in the UNIX passwd database. The fallback_transport_maps and fallback_transport parameters specify an optional message transport for recipients that are not found in the aliases(5) or UNIX passwd database.
In the case of UNIX-style mailbox delivery, the local(8) daemon prepends a "From sender time_stamp" envelope header to each message, prepends an X-Original-To: header with the recipient address as given to Postfix, prepends an optional Delivered-To: header with the final envelope recipient address, prepends a Return-Path: header with the envelope sender address, prepends a > character to lines beginning with "From ", and appends an empty line. The mailbox is locked for exclusive access while delivery is in progress. In case of problems, an attempt is made to truncate the mailbox to its original length.
In the case of maildir delivery, the local daemon prepends an optional Delivered-To: header with the final envelope recipient address, prepends an X-Original-To: header with the recipient address as given to Postfix, and prepends a Return-Path: header with the envelope sender address.
The allow_mail_to_commands configuration parameter restricts delivery to external commands. The default setting (alias, forward) forbids command destinations in :include: files.
Optionally, the process working directory is changed to the path specified with command_execution_directory (Postfix 2.2 and later). Failure to change directory causes mail to be deferred.
The command_execution_directory parameter value is subject to interpolation of $user (recipient username), $home (recipient home directory), $shell (recipient shell), $recipient (complete recipient address), $extension (recipient address extension), $domain (recipient domain), $local (entire recipient address localpart) and $recipient_delimiter. The forms ${name?value} and ${name:value} expand conditionally to value when $name is (is not) defined. Characters that may have special meaning to the shell or file system are replaced by underscores. The list of acceptable characters is specified with the execution_directory_expansion_filter configuration parameter.
The command is executed directly where possible. Assistance by the shell (/bin/sh on UNIX systems) is used only when the command contains shell magic characters, or when the command invokes a shell built-in command.
A limited amount of command output (standard output and standard error) is captured for inclusion with non-delivery status reports. A command is forcibly terminated if it does not complete within command_time_limit seconds. Command exit status codes are expected to follow the conventions defined in <sysexits.h>. Exit status 0 means normal successful completion.
Postfix version 2.3 and later support RFC 3463-style enhanced status codes. If a command terminates with a non-zero exit status, and the command output begins with an enhanced status code, this status code takes precedence over the non-zero exit status.
A limited amount of message context is exported via environment variables. Characters that may have special meaning to the shell are replaced by underscores. The list of acceptable characters is specified with the command_expansion_filter configuration parameter.
Additional remote client information is made available via the following environment variables:
The PATH environment variable is always reset to a system-dependent default path, and environment variables whose names are blessed by the export_environment configuration parameter are exported unchanged.
The current working directory is the mail queue directory.
The local(8) daemon prepends a "From sender time_stamp" envelope header to each message, prepends an X-Original-To: header with the recipient address as given to Postfix, prepends an optional Delivered-To: header with the final recipient envelope address, prepends a Return-Path: header with the sender envelope address, and appends no empty line.
The delivery format depends on the destination filename syntax. The default is to use UNIX-style mailbox format. Specify a name ending in / for qmail-compatible maildir delivery.
The allow_mail_to_files configuration parameter restricts delivery to external files. The default setting (alias, forward) forbids file destinations in :include: files.
In the case of UNIX-style mailbox delivery, the local(8) daemon prepends a "From sender time_stamp" envelope header to each message, prepends an X-Original-To: header with the recipient address as given to Postfix, prepends an optional Delivered-To: header with the final recipient envelope address, prepends a > character to lines beginning with "From ", and appends an empty line. The envelope sender address is available in the Return-Path: header. When the destination is a regular file, it is locked for exclusive access while delivery is in progress. In case of problems, an attempt is made to truncate a regular file to its original length.
In the case of maildir delivery, the local daemon prepends an optional Delivered-To: header with the final envelope recipient address, and prepends an X-Original-To: header with the recipient address as given to Postfix. The envelope sender address is available in the Return-Path: header.
The optional recipient_delimiter configuration parameter specifies how to separate address extensions from local recipient names.
For example, with "recipient_delimiter = +", mail for name+foo is delivered to the alias name+foo or to the alias name, to the destinations listed in ~name/.forward+foo or in ~name/.forward, to the mailbox owned by the user name, or it is sent back as undeliverable.
In all cases the local(8) daemon prepends an optional `Delivered-To: header line with the final recipient address.
Deliveries to external files and external commands are made with the rights of the receiving user on whose behalf the delivery is made. In the absence of a user context, the local(8) daemon uses the owner rights of the :include: file or alias database. When those files are owned by the superuser, delivery is made with the rights specified with the default_privs configuration parameter.
RFC 822 (ARPA Internet Text Messages) RFC 3463 (Enhanced status codes)
Depending on the setting of the notify_classes parameter, the postmaster is notified of bounces and of other trouble.
The local(8) delivery agent needs a dual personality 1) to access the private Postfix queue and IPC mechanisms, 2) to impersonate the recipient and deliver to recipient-specified files or commands. It is therefore security sensitive.
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.
Mutually-recursive aliases or ~/.forward files are not detected early. The resulting mail forwarding loop is broken by the use of the Delivered-To: message header.
Changes to main.cf are picked up automatically, as local(8) processes run for only a limited amount of time. Use the command "postfix reload" to speed up a change.
The text below provides only a parameter summary. See postconf(5) for more details including examples.
Available in Postfix version 2.3 and later:
The precedence of local(8) delivery methods from high to low is: aliases, .forward files, mailbox_transport_maps, mailbox_transport, mailbox_command_maps, mailbox_command, home_mailbox, mail_spool_directory, fallback_transport_maps, fallback_transport, and luser_relay.
Available in Postfix version 2.2 and later:
Available in Postfix version 2.2 and later:
The following are examples; details differ between systems. $HOME/.forward, per-user aliasing /etc/aliases, system-wide alias database /var/spool/mail, system mailboxes
qmgr(8), queue manager bounce(8), delivery status reports newaliases(1), create/update alias database postalias(1), create/update alias database aliases(5), format of alias database postconf(5), configuration parameters master(5), generic daemon options syslogd(8), system logging
The Secure Mailer license must be distributed with this software.
The Delivered-To: message header appears in the qmail system by Daniel Bernstein.
The maildir structure appears in the qmail system by Daniel Bernstein.
Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA
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