Two-Minute Drill

Here are some of the key points from the certification objectives in Chapter 12.

Mail Transport Agents, Mail Delivery Agents, and Mail User Agents

❑	Mail transport agents (MTA) are servers that carry e-mail to and from users.
❑	Three MTAs include sendmail, Postfix, and Dovecot.
❑	Mail user agents (MUA) are e-mail clients such as mail and Evolution.
❑	Mail delivery agents (MDA) are used with MTAs to transmit e-mail.

Reception with Dovecot

❑	The Dovecot service supports receipt of both POP3 and IMAP4 e-mail.
❑	Dovecot supports secure SSL versions of POP3 and IMAP4; you'll need to create SSL certificates in appropriate /etc/pki/dovecot directories.

sendmail Configuration

❑	The main sendmail configuration file is /etc/mail/sendmail.cf. It's easier to configure sendmail through its macro file, /etc/mail/sendmail.mc.
❑	You can customize the computers allowed to access your sendmail server through the access and virtusertable files in the /etc/mail directory.
❑	The make -C /etc/mail command processes all files in that directory, to configure sendmail completely.

Configuring and Activating Postfix

❑	The Postfix server is easier to configure through configuration files in the /etc/postfix directory. In fact, you can configure the main.cf file directly.
❑	Postfix also uses /etc/aliases to map and forward e-mail from old to new addresses.

Selecting an E-mail System

❑	RHEL 5 allows you to select between sendmail and Postfix. Don't activate both.
❑	Available tools for selecting a service are alternatives and system-switch-mail.
❑	Different mail clients can receive e-mail using the POP or IMAP protocols. Mail clients such as mail and mutt are available at the command line. GUI mail clients such as Thunderbird and Evolution are also available.