Mail Transport Agent (Mta) Configuration - Red Hat ENTERPRISE LINUX 3 System Administration Manual

Chapter 41.
Mail Transport Agent (MTA) Configuration
A Mail Transport Agent (MTA) is essential for sending email. A Mail User Agent (MUA) such as
Evolution, Mozilla Mail, and Mutt, is used to read and compose email. When a user sends an email
from an MUA, the messages are 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 command to send email containing log messages to the root user of the
/bin/mail
local system.
Red Hat Enterprise Linux 3 provides two MTAs: Sendmail and Postfix. If both are installed,
is the default MTA. The Mail Transport Agent Switcher allows for the selection of
sendmail
either or as the default MTA for the system.
sendmail postfix
The RPM package must be installed to use the text-based version of
redhat-switch-mail
the Mail Transport Agent Switcher program. If you want to use the graphical version, the
package must also be installed. For more information on installing
redhat-switch-mail-gnome
RPM packages, refer to Part III Package Management.
To start the Mail Transport Agent Switcher, select Main Menu Button (on the Panel) => Sys-
tem Tools => More System Tools => Mail Transport Agent Switcher, or type the command
at a shell prompt (for example, in an XTerm or GNOME terminal).
redhat-switch-mail
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 41-1. If X is not detected, it starts in
text-mode. To force Mail Transport Agent Switcher to run in text-mode, use the command
.
redhat-switch-mail-nox
Figure 41-1. Mail Transport Agent Switcher
If you select OK to change the MTA, the selected mail daemon is enabled to start at boot time, and the
unselected mail daemon is disabled so that is does not start at boot time. The selected mail daemon is
started, and the other mail daemon is stopped; thus making the changes take place immediately.
For more information about email protocols and MTAs, refer to the Red Hat Enterprise Linux Refer-
ence Guide.