Postfix: The Definitive Guide

Starting Postfix the First Time

There are two important issues to deal with before starting Postfix for the first time. The first is how your system identifies itself. Postfix uses a configuration parameter called myhostname , which must be set to the fully qualified hostname of the system Postfix is running on. Once Postfix knows the fully qualified hostname, it can use that hostname to set default values for other important parameters, such as mydomain. If the parameter myhostname is not set, Postfix defaults to the hostname reported by the system itself. There is a complete discussion of myhostname later in the chapter. You can see what name your system reports with the Unix hostname command:

$ hostname
mail.example.com

A fully qualified hostname is comprised of both the individual hostname and the domain in which it resides. Some systems are configured with their simple hostname, rather than its fully qualified version:

$ hostname
mail

If your system is configured with just its simple hostname, Postfix cannot determine what the fully qualified name is. You must therefore explicitly set the myhostname parameter. You can do this quite easily with the postconf Postfix command. The postconf command is a Postfix utility that provides an easy way to get a variety of information about your Postfix system. One of its functions is to display or change a specific configuration parameter. You can use it to set the myhostname parameter:

# postconf -e myhostname=mail.example.com

The -e