Chapter 2. Customizing sendmail Configuration Files

The sendmail program is a mail-transport agent and message router that uses a configuration file to provide aliasing and forwarding, automatic routing to network gateways, and flexible configuration. The Solaris environment supplies the standard configuration files that most sites can use.

With sendmail version 8.9.3, you no longer edit the sendmail.cf file directly. You should treat it as a binary that is not editable. Instead, you start with a file with a .mc (macro configuration) suffix and use the m4 macro processor to “compile” the .mc file into the final sendmail configuration file, which has a .cf suffix. See “Generating the sendmail Configuration File” for more information.

Because the m4 macro processor automatically generates the rules and rulesets in the sendmail.cf file from the macros you specify in the .mc file, you no longer need to write your own rules or rulesets.