Chainmail's operations are controlled by the configuration file. Without the configuration file chainmail is useless, since it won't do anything to your emails. The configuration file defines which emails chainmail processes, and what actions it performs on selected emails.
By default chainmail reads its configuration from the file /etc/chainmail.conf. An alternative configuration file may be specified by the --config command line option (see Chapter 4 for more inforation on chainmail command-line options).
Whitespace in the configuration file is generally ignored, so you can add blanks, tabs and newlines anywhere for readability. Only whitespace within quoted strings is not ignored, it is part of the quoted string. Comments are introduced by the '#' character and extend to the end of line. Case is not significant.
The configuration files consists of the following two sections:
options
rules
The options section specifies a number of options that control chainmail's overall behavior. The rules section specifies message processing rules.