    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=BFRhqu.> (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.

                  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 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 (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  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

                                                                    1