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PIPE(8) System Manager's Manual PIPE(8)

NAME

pipe - Postfix delivery to external command

SYNOPSIS

pipe [generic Postfix daemon options] command_attributes...

DESCRIPTION


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.

SINGLE-RECIPIENT DELIVERY



Some destinations cannot handle more than one recipient per
    delivery request. Examples are pagers or fax machines. In addition,
    multi-recipient delivery is undesirable when prepending a
    Delivered-to: or X-Original-To: message header.


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:



  

  
Change the process root directory and working directory to the named
      directory. This happens before switching to the privileges specified with
      the user attribute, and before executing the optional
      directory=pathname directive. Delivery is deferred in case
      of failure.
    
This feature is available as of Postfix 2.3.

  

  

  
Change to the named directory before executing the external command. The
      directory must be accessible for the user specified with the user
      attribute (see below). The default working directory is
      $queue_directory. Delivery is deferred in case of failure.
    
This feature is available as of Postfix 2.2.

  

  

  
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 \\.

  

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







  

  
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.

  

  
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 (see
      SINGLE-RECIPIENT DELIVERY above for details).
    
The D flag also enforces loop detection (Postfix 2.5
        and later): if a message already contains a Delivered-To: header
        with the same recipient address, then the message is returned as
        undeliverable. The address comparison is case insensitive.

    
This feature is available as of Postfix 2.0.

  

  

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

  

  
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
      (see SINGLE-RECIPIENT DELIVERY above for details).
    
This feature is available as of Postfix 2.0.

  

  

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

  

  
Indicate that the external command performs final delivery. This flag
      affects the status reported in "success" DSN (delivery status
      notification) messages, and changes it from "relayed" into
      "delivered".
    
This feature is available as of Postfix 2.5.

  

  

  
Fold the command-line $original_recipient and $recipient
      address domain part (text to the right of the right-most @
      character) to lower case; fold the entire command-line $domain and
      $nexthop host or domain information to lower case. This is
      recommended for delivery via UUCP.

  

  
Quote white space and other special characters in the command-line
      $sender, $original_recipient 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.

  

  

  
Fold the command-line $original_recipient and $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.







  

  
Replace the null sender address (typically used for delivery status
      notifications) with the specified text when expanding the $sender
      command-line macro, and when generating a From_ or Return-Path: message
      header.
    
If the null sender replacement text is a non-empty string then
        it is affected by the q flag for address quoting in command-line
        arguments.

    
The null sender replacement text may be empty; this form is
        recommended for content filters that feed mail back into Postfix. The
        empty sender address is not affected by the q flag for address
        quoting in command-line arguments.

    
Caution: a null sender address is easily mis-parsed by naive
        software. For example, when the pipe(8) daemon executes a command
        such as:

    

    


    Wrong: command -f$sender -- $recipient

  

  

  
the command will mis-parse the -f option value when the sender address is
      a null string. For correct parsing, specify $sender as an argument
      by itself:
    

    


    Right: command -f $sender -- $recipient

  

  

  
This feature is available as of Postfix 2.3.

  

  
Don't deliver messages that exceed this size limit (in bytes); return them
      to the sender instead.

  

  

  

  
Execute the external command with the user ID and group ID 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.

  

  
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 feature is available as of Postfix 2.2.

  

  
${client_helo}

  
This macro expands to the remote client HELO command parameter.
    
This feature is available as of Postfix 2.2.

  

  
${client_hostname}

  
This macro expands to the remote client hostname.
    
This feature is available as of Postfix 2.2.

  

  
${client_port}

  
This macro expands to the remote client TCP port number.
    
This feature is available as of Postfix 2.5.

  

  
${client_protocol}

  
This macro expands to the remote client protocol.
    
This feature is available as of Postfix 2.2.

  

  
${domain}

  
This macro expands to the domain portion of the recipient address. For
      example, with an address user+foo@domain the domain is
      domain.
    
This information is modified by the h flag for case
        folding.

    
This feature is available as of Postfix 2.5.

  

  
${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 to 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.

  

  
${original_recipient}

  
This macro expands to the complete recipient address before any address
      rewriting or aliasing.
    
A command-line argument that contains
        ${original_recipient} expands to as many command-line
        arguments as there are recipients.

    
This information is modified by the hqu flags for
        quoting and case folding.

    
This feature is available as of Postfix 2.5.

  

  
${recipient}

  
This macro expands to the complete recipient address.
    
A command-line argument that contains
        ${recipient} expands to 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 name of the SASL authentication mechanism in the
      AUTH command when the Postfix SMTP server received the message.
    
This feature is available as of Postfix 2.2.

  

  
${sasl_sender}

  
This macro expands to the SASL sender name (i.e. the original submitter as
      per RFC 4954) in the MAIL FROM command when the Postfix SMTP server
      received the message.
    
This feature is available as of Postfix 2.2.

  

  
${sasl_username}

  
This macro expands to the SASL user name in the AUTH command when the
      Postfix SMTP server received the message.
    
This feature is available as of Postfix 2.2.

  

  
${sender}

  
This macro expands to the envelope sender address. By default, the null
      sender address expands to MAILER-DAEMON; this can be changed with the
      null_sender attribute, as described above.
    
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.

  










STANDARDS


RFC 3463 (Enhanced status codes)






DIAGNOSTICS




Command exit status codes are expected to follow the conventions
    defined in <sysexits.h>. Exit status 0 means normal successful
    completion.


In the case of a non-zero exit status, a limited amount of command
    output is reported in an delivery status notification. When the output
    begins with a 4.X.X or 5.X.X enhanced status code, the status code takes
    precedence over the non-zero exit status (Postfix version 2.3 and
  later).


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




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.






RESOURCE AND RATE CONTROLS




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



  

  
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.

  

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

  

  
Limit the time for delivery to external command, for delivery via the
      named transport. The limit is enforced by the pipe delivery agent.
    
Postfix 2.4 and later support a suffix that specifies the time
        unit: s (seconds), m (minutes), h (hours), d (days), w (weeks). The
        default time unit is seconds.

  








MISCELLANEOUS CONTROLS





  

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

  

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

  

  
The maximal number of digits after the decimal point when logging
      sub-second delay values.

  

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

  

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

  

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

  

  
The maximum amount of time that an idle Postfix daemon process waits for
      an incoming connection before terminating voluntarily.

  

  
The maximal number of incoming connections that a Postfix daemon process
      will service before terminating voluntarily.

  

  
The process ID of a Postfix command or daemon process.

  

  
The process name of a Postfix command or daemon process.

  

  
The location of the Postfix top-level queue directory.

  

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

  

  
The syslog facility of Postfix logging.

  

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








SEE ALSO


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






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