Part I: A Tutorial

The first part of this tutorial is a tutorial intended mainly for those with a limited understanding of sendmail. Its aim is to provide the novice with a general introduction to V8 sendmail.

• Introduction
• Covers mail transfer agents and mail user agents, explains why sendmail is so complex, gives an overview of sendmail, and describes the differences between the header, body, and envelope of a mail message.
• Have a V8
• Shows where and how to get the source for V8 sendmail and how to compile and test a working binary.
• The Roles of sendmail
• Shows how sendmail processes aliases, queues messages for later transmission, does local and remote delivery, and runs in the background listening for incoming mail.
• How to Run sendmail
• Illustrates use of the -b (become), -v (verbose), and -d (debugging) command-line switches.
• The sendmail.cf File
• Provides a quick overview of all the commands found in the sendmail.cf file.
• The Mail Hub and Delivery Agents
• Describes the hub approach and shows how M (delivery agent) commands can be used to forward mail to a central hub machine.
• Macros
• Shows how text can be automatically propagated throughout the configuration file.
• Addresses and Rules
• Describes a fictional network, then uses addresses in that network to illustrate rules and rule sets.
• Rule Set 0
• Shows how rules in rule set 0 can select delivery agents and handle errors.
• Rule Set 3
• Explains rule set 3, the first to rewrite all addresses.
• Rule Sets 1 and S=
• Develops an S= rule set to make all mail appear as though it comes from the hub machine.
• Class
• Shows how multiple values can be referenced with a single expression in the LHS of rules.
• Setting Options
• Explains how options "tune" sendmail and offers a few suggestions.
• Headers, Precedence, and Trust
• Completes the client.cf file by adding H, P, and T commands.
• Install and Test the client.cf File
• Shows how to install the client.cf file as your working configuration file.
• The null.mc File and m4
• Shows how m4 can be used to produce a client.cf file called nullclient.
• The Hub's Complex Rules
• Concludes with a tour of a hub's major sendmail.cf file.