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.

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.