    PIPE(8)                                                   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 man-
           ager.

           Message  attributes  such  as  sender  address,  recipient
           address  and  next-hop  host name can be specified as com-
           mand-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 recipi-
           ent 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=BDFORhqu.> (optional)
                  Optional message processing flags.  By  default,  a
                  message is copied unchanged.

                  B      Append  a blank line at the end of each mes-
                         sage. 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_desti-
                         nation_recipient_limit must be 1.

                  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" mes-
                         sage header with the  recipient  address  as
                         given  to  Postfix.  Note: for this to work,
                         the    transport_destination_recipient_limit
                         must be 1.

                  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  charac-
                         ters in the command-line $sender and $recip-
                         ient 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 soft-
                         ware.

           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 (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 \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 exe-
                  cuted  directly,  i.e.  without  interpretation  of
                  shell  meta  characters  by  a shell command inter-
                  preter.

                  In  the  command  argument  vector,  the  following
                  macros are recognized and replaced with correspond-
                  ing 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 con-
           ventions defined in <sysexits.h>.

           Problems and transactions are logged to syslogd(8).   Cor-
           rupted  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  exe-
           cute external commands as the specified user. It is there-
           fore 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 mas-
           ter.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_desti-
                  nation_concurrency_limit  parameter.   The limit is
                  enforced by the Postfix queue manager.

           transport_destination_recipient_limit
                  Limit the number of recipients per  message  deliv-
                  ery,  for  delivery  via  the  named transport. The
                  default limit is taken  from  the  default_destina-
                  tion_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  parame-
                  ter.   The  limit  is enforced by the pipe delivery
                  agent.

    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

                                                              PIPE(8)