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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:

       chroot=pathname (optional)
              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.

       directory=pathname (optional)
              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.

       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=BDFORXhqu.>> (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 (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.

              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 (see SINGLE-RECIPIENT DELIVERY above for details).

                     This feature is available as of Postfix 2.0.

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

              X      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.

              h      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.

              q      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.

              u      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.

       null_sender=replacement (default: MAILER-DAEMON)
              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.

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

       user=username (required)

       user=username:groupname
              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.

       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 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.

       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.

              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

       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.

       delay_logging_resolution_limit (2)
              The maximal number of digits after the decimal point when
              logging sub-second delay values.

       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 an incoming connection before terminating voluntarily.

       max_use (100)
              The maximal number of incoming connections that a Postfix daemon
              process will service before terminating voluntarily.

       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 (see 'postconf -d' output)
              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



                                                                       PIPE(8)