PIPE(8)

NAME
pipe - Postfix delivery to external command

SYNOPSIS
pipe [generic Postfix daemon options] command_attributes...

DESCRIPTION
The pipe 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 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.

SINGLE-RECIPIENT DELIVERY
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.

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

flags=BFRhqu.> (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.

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

    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 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.

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.

eol=string (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 \octal and \\.

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

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:

    ${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.

    ${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.

In addition to the form ${name}, the forms $name and $(name) are also recognized. Specify $$ where a single $ is wanted.

DIAGNOSTICS
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.

SECURITY
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.

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

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

mail_owner
    The process privileges used while not running an external command.

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

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

transport_destination_recipient_limit
    Limit the number of recipients per message delivery, for delivery via the named transport. The default limit is taken from the default_destination_recipient_limit parameter. The limit is enforced by the Postfix queue manager.

transport_time_limit
    Limit the time for delivery to external command, for delivery via the named transport. The default limit is taken from the command_time_limit parameter. The limit is enforced by the Postfix queue manager.

SEE ALSO
bounce(8) non-delivery status reports
master(8) process manager
qmgr(8) queue manager
syslogd(8) system logging

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