Ingo, the "Email Filter Rules Manager", started as a frontend for
the Sieve filter language, and is now a generic and complete filter
rule frontend that currently is able to create Sieve, procmail,
maildrop, and IMAP filter rules. The IMAP filter driver translates
the filter rules on demand to IMAP commands, executed via PHP's IMAP
extension and has replaced IMP's internal filtering code. It is now
the default filtering agent in IMP H3 (4.x).