Most of the spam filtering done by MailWasher Enterprise Server is automatic, and it will start filtering spam instantly after you've set it up.
Filters capabilities are extensive.
Additionally, MailWasher Enterprise Server has all the features you'd expect
Mailwasher Enterprise Server is affordable and uses a low amount of resource (although it will use more if you give it more). Download your 30 day free trial today for Linux (or Windows) here. Detailed instructions for Microsoft Exchange can be found here.