What do I need to do to filter email on the server

Hi all,

I would like to implement mail filtering at the server level. My mail
agent is sendmail in conjuction with procmail/spamassassin and I use
Dovecot as the IMAP server.

Currently, I have a client machine (MacOS X) filtering the messages out
of the inbox into the appropriate slots, but that's a bit silly, if I
use another machine running evolution, to read mail. It would mean, the
Mac needs to run all the time to filter messages.

I'm not advocating MS Exchange here - But that's the kind of
functionality, I'd like to see with regards to mail filtering. I know,
Lotus Notes can do that, too - but that's not freeware either and there
is no native Notes Client for Linux.

Best regards,
Chris