17.1 Overall Syntax

The sendmail.cf file is line-oriented, with one configuration command per line. Each configuration command consists of a single letter^[1] that must begin a line. Each letter is followed by other information as required by the purpose of the particular command.

^[1] A quick bit of trivia: initially, there was almost nothing in the configuration file except R rules (and there was only one rule set). Eric recalls adding M and O fairly quickly. Commands such as K and V came quite late.

In addition to commands, the configuration file can also have lines that begin with a # to form a comment line, or with a tab or space character to form a continuation line. A list of all legal characters that can begin a line in the configuration file is shown in Table 17-1.

Table 17-1. sendmail.cf configuration commands

Command	§	Version	Description
#	Section 17.2	All	A comment line, ignored
space	Section 17.4	All	Continue the previous line
tab	Section 17.4	All	Continue the previous line
C	Section 22.1	All	Define a class macro
D	Section 21.3	All	Define a sendmail macro
E	Section 10.2.1	V8.7 and above	Environment for agents
F	Section 22.1	All	Define a class macro from a file or a pipe
H	Section 25.1	All	Define a header
K	Section 23.2	V8.1 and above	Create a keyed map entry
L		Obsolete	Extended load average
M	Section 20.1	All	Define a mail delivery agent
O	Section 24.3	All	Define an option
P	Section 25.10	All	Define delivery priorities
Q	Section 11.4.2	V8.12 and above	Declare queue groups
R	Section 18.2	All	Define a transformation rule
S	Section 19.1	All	Declare a rule-set start
T	Section 10.8.1.1	All	Declare trusted users (ignored V8.1-V8.6)
V	Section 17.5	V8.1 and above	Version of configuration file
X	Section 7.6.2	V8.12 and above	Define a mail filter for use

Most configuration commands are so complex that each requires a chapter or two of its own. A few, however, are simple. In this chapter we will describe the simple ones: comments, continuation lines, and the V (version) command.