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Lesson 3 sendmail agent
ObjectiveDescribe 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, we’ll 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 sendmail at proofpoint.com.
One of the most significant improvements in recent versions of 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.
Note: There are other MTA's in current use as well, including qmail.