pipe - Postfix delivery to external command

pipe [generic Postfix daemon options] command_attributes...

The pipe(8) daemon processes requests from the Postfix queue manager to deliver messages to external commands. This program expects to be run from the master(8) process manager.

Message attributes such as sender address, recipient address and next-hop host name can be specified as command-line macros that are expanded before the external command is executed.

The pipe(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.

Some external commands cannot handle more than one recipient per delivery request. Examples of such transports are pagers, fax machines, and so on.

To prevent Postfix from sending multiple recipients per delivery request, specify

transport_destination_recipient_limit = 1

in the Postfix main.cf file, where transport is the name in the first column of the Postfix master.cf entry for the pipe-based delivery transport.

The external command attributes are given in the master.cf file at the end of a service definition. The syntax is as follows:

directory=pathname (optional, default: $queue_directory)

Change to the named directory before executing the external command. Delivery is deferred in case of failure. This feature is available as of Postfix 2.2.

eol=string (optional, default: \n)

The output record delimiter. Typically one would use either \r\n or \n. The usual C-style backslash escape sequences are recognized: \a \b \f \n \r \t \v \ddd (up to three octal digits) and \\.

flags=BDFORhqu.> (optional)

Optional message processing flags. By default, a message is copied unchanged.

B

Append a blank line at the end of each message. This is required by some mail user agents that recognize "From " lines only when preceded by a blank line.

D

Prepend a "Delivered-To: recipient" message header with the envelope recipient address. Note: for this to work, the transport_destination_recipient_limit must be 1. This feature is available as of Postfix 2.0.

F

Prepend a "From sender time_stamp" envelope header to the message content. This is expected by, for example, UUCP software.

O

Prepend an "X-Original-To: recipient" message header with the recipient address as given to Postfix. Note: for this to work, the transport_destination_recipient_limit must be 1. This feature is available as of Postfix 2.0.

R

Prepend a Return-Path: message header with the envelope sender address.

h

Fold the command-line $recipient domain name and $nexthop host name to lower case. This is recommended for delivery via UUCP.

q

Quote white space and other special characters in the command-line $sender and $recipient address localparts (text to the left of the right-most @ character), according to an 8-bit transparent version of RFC 822. This is recommended for delivery via UUCP or BSMTP. The result is compatible with the address parsing of command-line recipients by the Postfix sendmail(1) mail submission command. The q flag affects only entire addresses, not the partial address information from the $user, $extension or $mailbox command-line macros.

u

Fold the command-line $recipient address localpart (text to the left of the right-most @ character) to lower case. This is recommended for delivery via UUCP.

.

Prepend "." to lines starting with ".". This is needed by, for example, BSMTP software.

>

Prepend ">" to lines starting with "From ". This is expected by, for example, UUCP software.

size=size_limit (optional)

Messages greater in size than this limit (in bytes) will be bounced back to the sender.

user=username (required)

user=username:groupname

The external command is executed with the rights of the specified username. The software refuses to execute commands with root privileges, or with the privileges of the mail system owner. If groupname is specified, the corresponding group ID is used instead of the group ID of username.

argv=command... (required)

The command to be executed. This must be specified as the last command attribute. The command is executed directly, i.e. without interpretation of shell meta characters by a shell command interpreter. In the command argument vector, the following macros are recognized and replaced with corresponding information from the Postfix queue manager delivery request. In addition to the form ${name}, the forms $name and $(name) are also recognized. Specify $$ where a single $ is wanted.

${client_address}

This macro expands to the remote client network address. This is available in Postfix 2.2 and later.

${client_helo}

This macro expands to the remote client HELO command parameter. This is available in Postfix 2.2 and later.

${client_hostname}

This macro expands to the remote client hostname. This is available in Postfix 2.2 and later.

${client_protocol}

This macro expands to the remote client protocol. This is available in Postfix 2.2 and later.

${extension}

This macro expands to the extension part of a recipient address. For example, with an address user+foo@domain the extension is foo. A command-line argument that contains ${extension} expands into as many command-line arguments as there are recipients. This information is modified by the u flag for case folding.

${mailbox}

This macro expands to the complete local part of a recipient address. For example, with an address user+foo@domain the mailbox is user+foo. A command-line argument that contains ${mailbox} expands into as many command-line arguments as there are recipients. This information is modified by the u flag for case folding.

${nexthop}

This macro expands to the next-hop hostname. This information is modified by the h flag for case folding.

${recipient}

This macro expands to the complete recipient address. A command-line argument that contains ${recipient} expands into as many command-line arguments as there are recipients. This information is modified by the hqu flags for quoting and case folding.

${sasl_method}

This macro expands to the SASL authentication mechanism used during the reception of the message. An empty string is passed if the message has been received without SASL authentication. This is available in Postfix 2.2 and later.

${sasl_sender}

This macro expands to the SASL sender name (i.e. the original submitter as per RFC 2554) used during the reception of the message. This is available in Postfix 2.2 and later.

${sasl_username}

This macro expands to the SASL user name used during the reception of the message. An empty string is passed if the message has been received without SASL authentication. This is available in Postfix 2.2 and later.

${sender}

This macro expands to the envelope sender address. This information is modified by the q flag for quoting.

${size}

This macro expands to Postfix's idea of the message size, which is an approximation of the size of the message as delivered.

${user}

This macro expands to the username part of a recipient address. For example, with an address user+foo@domain the username part is user. A command-line argument that contains ${user} expands into as many command-line arguments as there are recipients. This information is modified by the u flag for case folding.

Command exit status codes are expected to follow the conventions defined in <sysexits.h>.

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 for further inspection.

This program needs a dual personality 1) to access the private Postfix queue and IPC mechanisms, and 2) to execute external commands as the specified user. It is therefore security sensitive.

Changes to main.cf are picked up automatically as pipe(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.

In the text below, transport is the first field in a master.cf entry.

transport_destination_concurrency_limit ($default_destination_concurrency_limit)

Limit the number of parallel deliveries to the same destination, for delivery via the named transport. The limit is enforced by the Postfix queue manager.

transport_destination_recipient_limit ($default_destination_recipient_limit)

Limit the number of recipients per message delivery, for delivery via the named transport. The limit is enforced by the Postfix queue manager.

transport_time_limit ($command_time_limit)

Limit the time for delivery to external command, for delivery via the named transport. The limit is enforced by the pipe delivery agent.

config_directory (see 'postconf -d' output)

The default location of the Postfix main.cf and master.cf configuration files.

daemon_timeout (18000s)

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

export_environment (see 'postconf -d' output)

The list of environment variables that a Postfix process will export to non-Postfix processes.

ipc_timeout (3600s)

The time limit for sending or receiving information over an internal communication channel.

mail_owner (postfix)

The UNIX system account that owns the Postfix queue and most Postfix daemon processes.

max_idle (100s)

The maximum amount of time that an idle Postfix daemon process waits for the next service request before exiting.

max_use (100)

The maximal number of connection requests before a Postfix daemon process terminates.

process_id (read-only)

The process ID of a Postfix command or daemon process.

process_name (read-only)

The process name of a Postfix command or daemon process.

queue_directory (see 'postconf -d' output)

The location of the Postfix top-level queue directory.

recipient_delimiter (empty)

The separator between user names and address extensions (user+foo).

syslog_facility (mail)

The syslog facility of Postfix logging.

syslog_name (postfix)

The mail system name that is prepended to the process name in syslog records, so that "smtpd" becomes, for example, "postfix/smtpd".

qmgr(8), queue manager
bounce(8), delivery status reports
postconf(5), configuration parameters
master(5), generic daemon options
master(8), process manager
syslogd(8), system logging

The Secure Mailer license must be distributed with this software.

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