Chapter 16. Mail Transport Agent (MTA) Configuration

A Mail Transport Agent (MTA) is essential for sending email from a Red Hat Linux system. The Mail User Agent (MUA) such as Mozilla Mail, Mutt, Pine, and Evolution is used to read and compose email. When a user sends an email from an MUA, the messages is handed off to the MTA, which sends the message to a series of MTAs until it reaches its destination.

Even if a user does not plan to send email from the system, some automated tasks or system programs might use the /bin/mail command to send email containing log messages to the root user of the local system.

Red Hat Linux 7.3 provides two MTAs: Sendmail and Postfix. If both are installed, sendmail is the default MTA. Red Hat Mail Transport Agent Switcher allows a user to select either sendmail or postfix as the default MTA for the system.

To start Red Hat Mail Transport Agent Switcher, use one of the following methods:

• On the GNOME desktop, go to the Main Menu Button (on the Panel) => Programs => System => Red Hat Mail Transport Agent Switcher.

• On the KDE desktop, go to the Main Menu Button (on the Panel) System => Red Hat Mail Transport Agent Switcher.

• Type the command redhat-switchmail at a shell prompt (for example, in an XTerm or GNOME terminal).

The program automatically detect if the X Window System is running. If it is running, the program starts in graphical mode as shown in Figure 16-1. If X is not detected, it starts in text-mode. To force Red Hat Mail Transport Agent Switch to run in text-mode, use the command redhat-switchmail-nox.

If you selected Postfix, you must make sure the sendmail service is stopped and the postfix service is started:

/sbin/service sendmail stop
/sbin/service postfix start

If you selected Sendmail, you must make sure the postfix service is stopped and the sendmail service is started:

/sbin/service postfix stop
/sbin/service sendmail start

	Tip
	For more information about email protocols and MTAs, refer to the Official Red Hat Linux Reference Guide.