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Summary
There are servers that send e-mail, and servers that receive e-mail. Modern versions use some basic TCP/IP protocols: SMTP, POP3, and IMAP4. To send and receive e-mail through these protocols, you can choose among three types of mail services: MTA, MDA, and MUA. An MTA such as sendmail sends e-mail through a network. An MDA such as procmail takes messages from the Internet and stores them in spools, sometimes on incoming e-mail servers. An MUA is an e-mail client such as pine, KMail, Mozilla Mail, or Evolution.
sendmail is currently the most popular outgoing e-mail server on the Internet. Since editing the sendmail.cf configuration file is difficult, Red Hat provides a macro file, sendmail.mc, which can be more easily understood and edited. It is easy to convert into sendmail.cf with the m4 macro processor. There are other important sendmail configuration files, including /etc/sysconfig/sendmail and /etc/aliases, as well as other files in the /etc/mail directory. Once you have your new sendmail.cf file, you can make the sendmail daemon reread it with the service sendmail restart command.
There are two basic options for e-mail servers that conform to the POP3 and IMAP4 protocols. Secure versions of each server are available. All are xinetd services that can be installed from the imap-* RPM package. Once these services are installed and activated, your users will need a username and the FQDN of the e-mail server. If it’s an IMAP4 server, they’ll also need a home directory for their e-mail files.
Both text and graphical e-mail clients are available. One useful highly configurable text-based client is pine. Graphical e-mail clients are available in a number of forms, including Evolution, Mozilla Mail, and KMail.
In the next chapter, we’ll take a look at various FTP clients and servers. The FTP client is flexible; you can even use FTP commands to connect and upgrade your RPMs. You can install anonymous, standard, and even secure FTP servers on your Red Hat Linux computer.
