|Lesson 3 ||sendmail agent|
|Objective||Describe the advantages of using the latest version of sendmail.|
Sendmail Agent (Advantages)
The oldest and the most commonly used Mail Transfer Agent on the Internet is
sendmail. It is delivered as part of many standard UNIX distributions, including Solaris and Linux.
In this course, well be using
sendmail 8.8.9. More recent releases of
sendmail are somewhat easier to configure. In addition,
sendmail has tended to be extremely vulnerable to security weaknesses. For these reasons, you should use the most current version of
sendmail as possible. You can obtain
One of the most significant improvements in recent versions of
There are other MTA's in current use as well, including qmail.
sendmail is the adoption of a simplified configuration scheme. The
sendmail agent is controlled by a configuration file (sendmail.cf) that is notoriously complicated. Beginning with
sendmail 8.7, you can assemble your configuration file by putting together pieces of code written in a macro language called M4, and then using M4 to generate the final configuration file. As you learn about configuring
sendmail, you will learn about how to use M4.
Before you learn about configuring
sendmail, however, you need to learn more about how
sendmail implements SMTP (Simple Mail
Transfer Protocol). The
sendmail agent runs as a daemon program. It relays, or transfers, email between machines using the SMTP
protocol or an older, essentially obsolete protocol called UUCP (UNIX to UNIX Copy). We will concentrate entirely on SMTP.