Installation guide

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.
Figure 16-1. Red Hat Mail Transport Agent Switcher