How do I start / stop / restart my postfix mail server under Linux or UNIX operating systems?

You can use the following commands to start / stop and restart mail system. Please note that the following commands are reserved for the superuser i.e. you must be root to run them.

UNIX / Linux Postfix Control Program

The postfix command controls the operation of the Postfix mail system: start or stop the master daemon, do a health check, and other maintenance.

Task: Stop Postfix

Type the following command:
# postfix stop

Task: Start Postfix

Type the following command:
# postfix start

Task: Restart Postfix

Type the following command:
# postfix stop && postfix start

Task: Reload Postfix

To re-read configuration files, enter:
# postfix reload
The following distribution specific commands can be used too.

Debain / Ubuntu Linux Postfix Start / Stop / Restart Command

Type the following commands:
$ sudo /etc/init.d/postfix start
$ sudo /etc/init.d/postfix stop
$ sudo /etc/init.d/postfix restart
OR
$ sudo service postfix start
$ sudo service postfix stop
$ sudo service postfix restart

RHEL / CentOS / Fedora Linux Postfix Start / Stop / Restart Command

# /sbin/service postfix start
# /sbin/service postfix stop
# /sbin/service postfix restart