15.3 About the Postfix SMTP Server

Postfix is configured as the default MTA on Oracle Linux. Although Postfix does not have as many features as Sendmail, it is easier to administer than Sendmail and its features are sufficient to meet the requirements of most installations. You should only use Sendmail if you want to use address re-writing rules or mail filters (milters) that are specific to Sendmail. Most mail filters function correctly with Postfix. If you do use Sendmail, disable or uninstall Postfix to avoid contention over network port usage.

Postfix has a modular design that consists of a master daemon and several smaller processes. Postfix stores its configuration files in the /etc/postfix directory, including:


Specifies which hosts are allowed to connect to Postfix.


Contains global configuration options for Postfix.


Specifies how the Postfix master daemon and other Postfix processes interact to deliver email.


Specifies the mapping between destination email addresses and relay hosts.

By default, Postfix does not accept network connections from any system other than the local host. To enable mail delivery for other hosts, edit /etc/postfix/main.cf and configure their domain, host name, and network information.

Restart the Postfix service after making any configuration changes:

# service postfix restart

For more information, see postfix(1) and other Postfix manual pages, Section 15.5, “Forwarding Email”, /usr/share/doc/postfix-version, and http://www.postfix.org/documentation.html.