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myorigin = $mydomain

Some Linux distributions that already include Postfix configure it to use Procmail by default. Procmail is a separate mail delivery agent (MDA) that can filter and sort mail as it makes deliveries to individual users on your system. We describe Procmail in more detail later in this chapter. If you need the features it provides, you should study the Procmail documentation carefully to understand how it interacts with Postfix. For many systems that don't filter mail for users at the MTA level, Procmail is an unnecessary additional layer of complexity because Postfix can also make local deliveries and provide some of the same functions. Your distribution might be configured to use Procmail in either the mailbox_command or mailbox_transport parameters. If you want Postfix to handle local deliveries directly, you can safely comment out either of these parameters in your /etc/postfix/main.cf file.

Starting Postfix

Once you have verified the important configuration parameters described earlier and rebuilt your aliases index file, you are ready to start Postfix. As the superuser, execute:

postfix start

You can stop Postfix by executing:

postfix stop

Whenever you make changes to either of Postfix's configuration files, you must reload the running Postfix image by executing:

postfix reload

Once you have Postfix running, all the users on your system should be able to send and receive email messages.

Any of your applications that depend on sendmail should still work, and you can use the sendmail command as you always did. You can pipe messages to it from within scripts and execute sendmail -q to flush the queue. The native Postfix equivalent for flushing the queue is postfix flush. Options to sendmail that deal with it running as a daemon and setting queue delays do not work because those functions are not handled by the sendmail command in Postfix. All the Postfix options are set in its two configuration files. Many parameters deal with the Postfix queue. You can find them in the manpage for qmgr(8).

Postfix Logging

After starting or reloading Postfix, you should check the log to see if Postfix reports any problems. (Most Linux distributions use /var/log/maillog, but you can also check the file /etc/syslog.conf to be sure.) You can see Postfix's most recent messages by running the command tail /var/log/maillog. Since Postfix is a long-running process, it's a good idea to check the log periodically even if you haven't been restarting it. You can execute the following to see if Postfix has reported anything interesting while running:

egrep '(reject|warning|error|fatal|panic):' /var/log/maillog

In general, Postfix keeps you informed of what is going on with your system by logging lots of good information to syslogd. On Linux, syslogd uses synchronous writes by default, which means that after every write to the logfile, there is also a sync to force everything in memory to be written to the disk. Therefore, the performance of Postfix (and other processes) can suffer. You can change this default by preceding the name of the logfile with a hyphen in /etc/syslog.conf. Your entry in syslog.conf for mail logging should look like the following:

mail.* -/var/log/maillog

Be sure to have syslogd reread its configuration file after you make any changes. You can execute killall -HUP syslogd to reinitialize it.

Running Postfix on System Startup

Because of Postfix's compatibility with sendmail, if you have your system configured to start sendmail at system initialization, more than likely Postfix will start correctly when your system boots. However, system shutdown will probably not work correctly. Most Linux distributions shut down sendmail by locating a process called sendmail and then killing that process. The Postfix processes, while in many ways compatible with sendmail, do not run under the name sendmail, so this shutdown fails.

If you would like your system to shut down cleanly, you should create your own rc script for Postfix, as described in "rc Files" in Chapter