Chapter 23. Mail Transport Agent (MTA) Configuration
A Mail Transport Agent (MTA) is essential for
sending email from a Red Hat Linux system. 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 /bin/mail
command to send email containing log messages to the root user of the
local system.
Red Hat Linux 9 provides two MTAs: Sendmail and Postfix. If both are
installed, sendmail is the default MTA. The
Mail Transport Agent Switcher allows for the selection of
either sendmail or postfix as the
default MTA for the system.
The redhat-switch-mail RPM package must be installed to
use the text-based version of the
Mail Transport Agent Switcher program. If you want to use the
graphical version, the redhat-switch-mail-gnome package
must also be installed.
For more information on installing RPM packages,
refer to Part V Package Management.
To start the Mail Transport Agent Switcher, select
(on the Panel) =>
=> =>
, or type the command
redhat-switch-mail 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 23-1. 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.
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 Linux Reference Guide. For more information about MUAs, refer to
the Red Hat Linux Getting Started Guide.
