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MASTER(5)                     File Formats Manual                    MASTER(5)

       master - Postfix master process configuration file format

       The Postfix mail system is implemented by small number of (mostly)
       client commands that are invoked by users, and by a larger number of
       services that run in the background.

       Postfix services are implemented by daemon processes. These run in the
       background under control of the master(8) process.  The master.cf
       configuration file defines how a client program connects to a service,
       and what daemon program runs when a service is requested.  Most daemon
       processes are short-lived and terminate voluntarily after serving
       max_use clients, or after inactivity for max_idle or more units of

       All daemons specified here must speak a Postfix-internal protocol. In
       order to execute non-Postfix software use the local(8), pipe(8) or
       spawn(8) services, or run the server under control by inetd(8) or

       After changing master.cf you must execute "postfix reload" to reload
       the configuration.

       The general format of the master.cf file is as follows:

       ⊕      Empty lines and whitespace-only lines are ignored, as are lines
              whose first non-whitespace character is a `#'.

       ⊕      A logical line starts with non-whitespace text. A line that
              starts with whitespace continues a logical line.

       ⊕      Each logical line defines a single Postfix service.  Each
              service is identified by its name and type as described below.
              When multiple lines specify the same service name and type, only
              the last one is remembered.  Otherwise, the order of master.cf
              service definitions does not matter.

       Each logical line consists of eight fields separated by whitespace.
       These are described below in the order as they appear in the master.cf

       Where applicable a field of "-" requests that the built-in default
       value be used. For boolean fields specify "y" or "n" to override the
       default value.

       Service name
              The service name syntax depends on the service type as described

       Service type
              Specify one of the following service types:

              inet   The service listens on a TCP/IP socket and is accessible
                     via the network.

                     The service name is specified as host:port, denoting the
                     host and port on which new connections should be
                     accepted. The host part (and colon) may be omitted.
                     Either host or port may be given in symbolic form (host
                     or service name) or in numeric form (IP address or port
                     number).  Host information may be enclosed inside "[]";
                     this form is necessary only with IPv6 addresses.

                     Examples: a service named or ::1:smtp
                     receives mail via the loopback interface only; and a
                     service named 10025 accepts connections on TCP port 10025
                     via all interfaces configured with the inet_interfaces

                     Note: with Postfix version 2.2 and later specify
                     "inet_interfaces = loopback-only" in main.cf, instead of
                     hard-coding loopback IP address information in master.cf
                     or in main.cf.

              unix   The service listens on a UNIX-domain socket and is
                     accessible for local clients only.

                     The service name is a pathname relative to the Postfix
                     queue directory (pathname controlled with the
                     queue_directory configuration parameter in main.cf).

                     On Solaris 8 and earlier systems the unix type is
                     implemented with streams sockets.

              fifo   The service listens on a FIFO (named pipe) and is
                     accessible for local clients only.

                     The service name is a pathname relative to the Postfix
                     queue directory (pathname controlled with the
                     queue_directory configuration parameter in main.cf).

              pass   The service listens on a UNIX-domain socket, and is
                     accessible to local clients only. It receives one open
                     connection (file descriptor passing) per connection

                     The service name is a pathname relative to the Postfix
                     queue directory (pathname controlled with the
                     queue_directory configuration parameter in main.cf).

                     On Solaris 8 and earlier systems the pass type is
                     implemented with streams sockets.

                     This feature is available as of Postfix version 2.5.

       Private (default: y)
              Whether or not access is restricted to the mail system.
              Internet (type inet) services can't be private.

       Unprivileged (default: y)
              Whether the service runs with root privileges or as the owner of
              the Postfix system (the owner name is controlled by the
              mail_owner configuration variable in the main.cf file).

              The local(8), pipe(8), spawn(8), and virtual(8) daemons require

       Chroot (default: Postfix >= 3.0: n, Postfix <3.0: y)
              Whether or not the service runs chrooted to the mail queue
              directory (pathname is controlled by the queue_directory
              configuration variable in the main.cf file).

              Chroot should not be used with the local(8), pipe(8), spawn(8),
              and virtual(8) daemons.  Although the proxymap(8) server can run
              chrooted, doing so defeats most of the purpose of having that
              service in the first place.

              The files in the examples/chroot-setup subdirectory of the
              Postfix source archive show set up a Postfix chroot environment
              on a variety of systems. See also BASIC_CONFIGURATION_README for
              issues related to running daemons chrooted.

       Wake up time (default: 0)
              Automatically wake up the named service after the specified
              number of seconds. The wake up is implemented by connecting to
              the service and sending a wake up request.  A ? at the end of
              the wake-up time field requests that no wake up events be sent
              before the first time a service is used.  Specify 0 for no
              automatic wake up.

              The pickup(8), qmgr(8) and flush(8) daemons require a wake up

       Process limit (default: $default_process_limit)
              The maximum number of processes that may execute this service
              simultaneously. Specify 0 for no process count limit.

              NOTE: Some Postfix services must be configured as a
              single-process service (for example, qmgr(8)) and some services
              must be configured with no process limit (for example,
              cleanup(8)).  These limits must not be changed.

       Command name + arguments
              The command to be executed.  Characters that are special to the
              shell such as ">" or "|" have no special meaning here, and
              quotes cannot be used to protect arguments containing
              whitespace. To protect whitespace, use "{" and "}" as described

              The command name is relative to the Postfix daemon directory
              (pathname is controlled by the daemon_directory configuration

              The command argument syntax for specific commands is specified
              in the respective daemon manual page.

              The following command-line options have the same effect for all
              daemon programs:

              -D     Run the daemon under control by the command specified
                     with the debugger_command variable in the main.cf
                     configuration file.  See DEBUG_README for hints and tips.

              -o { name = value } (long form, Postfix >= 3.0)

              -o name=value (short form)
                     Override the named main.cf configuration parameter. The
                     parameter value can refer to other parameters as $name
                     etc., just like in main.cf.  See postconf(5) for syntax.

                     NOTE 1: With the "long form" shown above, whitespace
                     after "{", around "=", and before "}" is ignored, and
                     whitespace within the parameter value is preserved.

                     NOTE 2: with the "short form" shown above, do not specify
                     whitespace around the "=" or in parameter values. To
                     specify a parameter value that contains whitespace, use
                     the long form described above, or use commas instead of
                     spaces, or specify the value in main.cf. Example:

                         submission inet .... smtpd
                             -o smtpd_xxx_yyy=$submission_xxx_yyy

                         submission_xxx_yyy = text with whitespace...

                     NOTE 3: Over-zealous use of parameter overrides makes the
                     Postfix configuration hard to understand and maintain.
                     At a certain point, it might be easier to configure
                     multiple instances of Postfix, instead of configuring
                     multiple personalities via master.cf.

              -v     Increase the verbose logging level. Specify multiple -v
                     options to make a Postfix daemon process increasingly

              Other command-line arguments
                     Specify "{" and "}" around command arguments that contain
                     whitespace (Postfix 3.0 and later). Whitespace after "{"
                     and before "}" is ignored.

       master(8), process manager
       postconf(5), configuration parameters

       Use "postconf readme_directory" or "postconf html_directory" to locate
       this information.
       BASIC_CONFIGURATION_README, basic configuration
       DEBUG_README, Postfix debugging

       The Secure Mailer license must be distributed with this software.

       Initial version by
       Magnus Baeck
       Lund Institute of Technology

       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA