Linux offers a number of alternative methods for handling incoming and outgoing e-mail. Red Hat Enterprise Linux includes sendmail, Postfix, and Dovecot for this purpose. (Yes, it includes exim and squirrelmail as well, but sendmail, Postfix, and Dovecot are what's listed in the RH300 course outline, and Dovecot is the new default for incoming e-mail.)
Perhaps the most common server for outgoing e-mail is sendmail, which may already be installed on your RHEL system. Once it is installed and configured, you can set up sendmail as your own personal mail server (subject to the limitations of your ISP). RHEL includes the open-source version of sendmail; the commercial version is known as Sendmail (with the capital S). One alternative to sendmail that is installed on RHEL is known as Postfix.
RHEL includes Dovecot for standard incoming e-mail protocols. It's relatively easy to configure these protocols, including POP3 (Post Office Protocol), POP3S (the secure version), IMAP (Internet Message Access Protocol), and IMAPS (the secure version).
A number of alternatives to sendmail are not covered in this book; they include procmail, mail.local, exim, Cyrus IMAP, and uucp. Only sendmail, Postfix, and Dovecot are currently part of Red Hat's public RH300 course outline.
More Network Services
This chapter is focused on the RHCE exam. While the ability to configure an e-mail client is a prerequisite skill for both exams, the Red Hat Exam Prep guide suggests that RHCE candidates must know how to configure the following network services:
IMAP, IMAPS, and POP3
While sendmail and Postfix are not specified in the Exam Prep guide, the RHCE course, RH300, includes coverage of Dovecot, sendmail, and Postfix. Dovecot is one RHEL 5 service that can handle IMAP, IMAPS, and POP3.
This chapter is related to the following items on the Troubleshooting and System Maintenance portion of the RHCE exam:
Diagnose and correct problems with network services, including whatever mail related services that you've configured.
There's also the related Troubleshooting and System Maintenance requirement to
Diagnose and correct networking services problems where SELinux contexts are interfering with proper operation.
But the only e-mail related option is to disable SELinux protection for Postfix (and fetchmail).
You may need to install, configure, and secure these services during the Installation and Configuration portion of the exam. And don't forget to make sure any required services are active when you reboot, or you may not get credit for your work.
As for the RHCE exam, you may have to configure or troubleshoot the e-mail services discussed in this chapter. So as you read this chapter and look through the configuration files and exercises, be willing to experiment. And practice, practice, practice what you learn.