Sieve

An e-mail filtering language supported by the Cyrus daemon, and defined in RFC:3028. Think of it as procmail for human beings, since it seems to be actually readable and understandable six months after you’ve defined your filters.

• What’s left of the home page.
• A quick overview (includes draft specs for the filtering language)
• avelsieve, a Squirrelmail plugin (via this post regarding enabling timsieved on Mac OS X).
• websieve