In general, the default policy.siv file is comprised of eight if control statements and one else statement. Each control statement is comprised of a type of test, a block and an associated sequence of actions. Action sequences can either modify or route particular messages in PureMessage. Actions, tests, and commands specific to PureMessage are prefixed with pmx_ to identify the command as an extension to Sieve.

For the purpose of discussion, the policy.siv file is broken into six parts. Each script piece is followed by a detailed description of the commands and syntax used to filter mail in PureMessage.