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Chapter 19t CHAPTER 19
The S (Rule Sets)
Configuration Command
Rule sets in the configuration file, like subroutines in a program, control the
sequence of steps sendmail uses to rewrite addresses. Inside eachrule set is a series of
zero or more individual rules. Rules are used to select the appropriate delivery agent
for any particular address, to detect and reject addressing errors, to transform
addresses to meet particular needs, to validate addresses and headers for the purpose
of rejecting spam, and to make policy decisions.
In this chapter, we will cover all aspects of rule sets, showing that rule sets are called
in particular orders and explaining why this is so.
We will explain many of the rules that typically appear in rule sets. But be forewarned:
the examples of rules in this chapter are only explanatory. Your sendmail.cf
file is likely to have rules that are somewhat different. Copying or using these examples,
without first understanding the underlying principles, can cause email to begin
to fail.
19.1 The S Configuration Command
The S configuration command declares the start of a rule set. It is perhaps the simplest
of all configuration commands and looks like this:
Sident
The S, like all configuration commands, must begin the line. The ident identifies the
rule set. There can be whitespace between the S and the ident.
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