Chapter 17. Configuration File Overview

The sendmail configuration file (usually called sendmail.cf, but for MSP submission, called submit.cf) provides all the central information that controls the sendmail program's behavior. Among the key pieces of information provided are the following:

• The location of all the other files that sendmail needs to access and the location of all the directories in which sendmail needs to create and remove files.

• The definitions that sendmail uses in rewriting addresses. Some of those definitions can come from files, which are also specified.

• The mail header lines that sendmail should modify, pass through, and/or augment.

• The rules and sets of rules that sendmail uses for transforming mail addresses (and aliases for those addresses) into usable information, such as which delivery agent to use and the correct form of the address to use with that delivery agent.

• The external programs though which sendmail should filter messages to detect and eliminate spam and viruses.

The location of the sendmail.cf (and submit.cf) file is compiled into sendmail. Beginning with V8.10, sendmail expects to find its configuration file in the /etc/mail directory. Prior to V8.10, the configuration file was usually found in either the /etc, the /usr/lib, or the /etc/mail directory. (See _PATH... for a description of how to change the default.) We recommend that the standard /etc/mail location be used unless you have a compelling reason to do otherwise. A nonstandard location can, for example, make operating system upgrades difficult.

The configuration file is read and parsed by sendmail every time it starts up. Because sendmail is run every time electronic mail is sent, its configuration file is designed to be easy for sendmail to parse rather than easy for humans to read.