Sendmail, 3rd Edition

The sendmail.cf File

The sendmail.cf file is read and parsed by sendmail every time sendmail starts. It contains information that is necessary for sendmail to run. It lists the locations of important files and specifies the default permissions for those files. It contains options that modify sendmail’s behavior. Most important, it contains rules and rule sets for rewriting addresses.

Configuration Commands

The sendmail.cf configuration file is line-oriented. A configuration command, composed of a single letter, begins each line:

V9/Berkeley                   ←good
 V9/Berkeley                  ←bad, does not begin a line
V9/Berkeley Fw/etc/mail/mxhosts   ←bad, two commands on one line
Fw/etc/mail/mxhosts←good

Each configuration command is followed by parameters that are specific to it. For example, the V command is followed by a number, a slash, and a vendor name. Whereas the F command is followed by a letter (a w in the example), then the full pathname of a file. The complete list of configuration commands^[18] is shown in Table 1-4.

Table 1-4. The sendmail.cf file’s configuration commands

Command	Description
C	Define a class macro
D	Define a macro
E	Define an environment variable (beginning with V8.7)
F	Define a class macro from a file, pipe, or database map
H	Define a header
K	Declare a keyed database (beginning with V8.1)
L	Include extended load average support (contributed software, not covered)
M	Define a mail delivery agent
O	Define an option
P	Define delivery priorities
Q	Define a queue ...