LOCAL(8)

NAME
local - Postfix local mail delivery

SYNOPSIS
local [generic Postfix daemon options]

DESCRIPTION
The local daemon processes delivery requests from the Postfix queue manager to deliver mail to local recipients. Each delivery request specifies a queue file, a sender address, a domain or host to deliver to, and one or more recipients. This program expects to be run from the master(8) process manager. The local 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 problem reports are sent to the bounce(8) or defer(8) daemon as appropriate.

SYSTEM-WIDE AND USER-LEVEL ALIASING
The system adminstrator 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. 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.

MAIL FORWARDING
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 envelope recipient address. If mail arrives for a recipient that is already listed in a Delivered-To: header, the message is bounced.

MAILBOX DELIVERY
The default per-user mailbox is a file in the UNIX mail spool directory (/var/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 configuration parameter. The command executes with the privileges of the recipient user (exception: 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 configuration parameter specifies a 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 parameter specifies a message transport for recipients that are not found in the UNIX passwd database. In the case of UNIX-style mailbox delivery, the local daemon prepends a "From sender time_stamp" envelope header to each message, prepends an optional Delivered-To: header with the 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 envelope recipient address and prepends a Return-Path: header with the envelope sender address.

EXTERNAL COMMAND DELIVERY
The allow_mail_to_commands configuration parameter restricts delivery to external commands. The default setting (alias, forward) forbids command destinations in :include: files. 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>. 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.

SHELL
    The recipient user's login shell.

HOME
    The recipient user's home directory.

USER
    The bare recipient name.

EXTENSION
    The optional recipient address extension.

DOMAIN
    The recipient address domain part.

LOGNAME
    The bare recipient name.

LOCAL
    The entire recipient address localpart (text to the left of the rightmost @ character).

RECIPIENT
    The entire recipient address.

The PATH environment variable is always reset to a system-dependent default path, and the TZ (time zone) environment variable is always passed on without change. The current working directory is the mail queue directory. The local daemon prepends a "From sender time_stamp" envelope header to each message, prepends an optional Delivered-To: header with the recipient envelope address, prepends a Return-Path: header with the sender envelope address, and appends no empty line.

EXTERNAL FILE DELIVERY
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 daemon prepends a "From sender time_stamp" envelope header to each message, prepends an optional Delivered-To: header with the 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 envelope recipient address. The envelope sender address is available in the Return-Path: header.

ADDRESS EXTENSION
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 daemon prepends an optional `Delivered-To: name+foo' header line.

DELIVERY RIGHTS
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 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.

STANDARDS
RFC 822 (ARPA Internet Text Messages)

DIAGNOSTICS
Problems and transactions are logged to syslogd(8). Corrupted message files are marked so that the queue manager can move them to the corrupt queue afterwards. Depending on the setting of the notify_classes parameter, the postmaster is notified of bounces and of other trouble.

BUGS
For security reasons, the message delivery status of external commands or of external files is never checkpointed to file. As a result, the program may occasionally deliver more than once to a command or external file. Better safe than sorry. 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.

CONFIGURATION PARAMETERS
The following main.cf parameters are especially relevant to this program. See the Postfix main.cf file for syntax details and for default values. Use the postfix reload command after a configuration change.

Miscellaneous

alias_maps
    List of alias databases.

biff
    Enable or disable notification of new mail via the comsat network service.

expand_owner_alias
    When delivering to an alias that has an owner- companion alias, set the envelope sender address to the right-hand side of the owner alias, instead using of the left-hand side address.

export_environment
    List of names of environment parameters that can be exported to non-Postfix processes.

forward_path
    Search list for .forward files. The names are subject to $name expansion.

local_command_shell
    Shell to use for external command execution (for example, /some/where/smrsh -c). When a shell is specified, it is invoked even when the command contains no shell built-in commands or meta characters.

owner_request_special
    Give special treatment to owner-xxx and xxx-request addresses.

prepend_delivered_header
    Prepend an optional Delivered-To: header upon external forwarding, delivery to command or file. Specify zero or more of: command, file, forward. Turning off Delivered-To: when forwarding mail is not recommended.

recipient_delimiter
    Separator between username and address extension.

require_home_directory
    Require that a recipient's home directory is accessible by the recipient before attempting delivery. Defer delivery otherwise.

Mailbox delivery

fallback_transport
    Message transport for recipients that are not found in the UNIX passwd database. This parameter overrides luser_relay.

home_mailbox
    Pathname of a mailbox relative to a user's home directory. Specify a path ending in / for maildir-style delivery.

luser_relay
    Destination (@domain or address) for non-existent users. The address is subjected to $name expansion.

mail_spool_directory
    Directory with UNIX-style mailboxes. The default pathname is system dependent. Specify a path ending in / for maildir-style delivery.

mailbox_command
    External command to use for mailbox delivery. The command executes with the recipient privileges (exception: root). The string is subject to $name expansions.

mailbox_command_maps
    Lookup tables with per-recipient external commands to use for mailbox delivery. Behavior is as with mailbox_command.

mailbox_transport
    Message transport to use for mailbox delivery to all local recipients, whether or not they are found in the UNIX passwd database. This parameter overrides all other configuration parameters that control mailbox delivery, including luser_relay.

Locking controls

deliver_lock_attempts
    Limit the number of attempts to acquire an exclusive lock on a mailbox or external file.

deliver_lock_delay
    Time in seconds between successive attempts to acquire an exclusive lock.

stale_lock_time
    Limit the time after which a stale lock is removed.

mailbox_delivery_lock
    What file locking method(s) to use when delivering to a UNIX-style mailbox. The default setting is system dependent. For a list of available file locking methods, use the postconf -l command.

Resource controls

command_time_limit
    Limit the amount of time for delivery to external command.

duplicate_filter_limit
    Limit the size of the duplicate filter for results from alias etc. expansion.

line_length_limit
    Limit the amount of memory used for processing a partial input line.

local_destination_concurrency_limit
    Limit the number of parallel deliveries to the same user. The default limit is taken from the default_destination_concurrency_limit parameter.

local_destination_recipient_limit
    Limit the number of recipients per message delivery. The default limit is taken from the default_destination_recipient_limit parameter.

mailbox_size_limit
    Limit the size of a mailbox etc. file (any file that is written to upon delivery). Set to zero to disable the limit.

Security controls

allow_mail_to_commands
    Restrict the usage of mail delivery to external command. Specify zero or more of: alias, forward, include.

allow_mail_to_files
    Restrict the usage of mail delivery to external file. Specify zero or more of: alias, forward, include.

command_expansion_filter
    What characters are allowed to appear in $name expansions of mailbox_command. Illegal characters are replaced by underscores.

default_privs
    Default rights for delivery to external file or command.

forward_expansion_filter
    What characters are allowed to appear in $name expansions of forward_path. Illegal characters are replaced by underscores.

HISTORY
The Delivered-To: header appears in the qmail system by Daniel Bernstein. The maildir structure appears in the qmail system by Daniel Bernstein.

SEE ALSO
aliases(5) format of alias database
bounce(8) non-delivery status reports
postalias(1) create/update alias database
syslogd(8) system logging
qmgr(8) queue manager

LICENSE
The Secure Mailer license must be distributed with this software.

AUTHOR(S)
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA