I get a lot of email that matters to me: often a hundred messages a day. I get even more spam sent to me: thousands of messages a day. I manage this successfully with multiple filters, multiple servers, and multiple email addresses. You might not be able to apply all of my techniques, but some of them might help you.

Bayesian Filters at the Email Client
I used to funnel all my email to a single POP3 client, and filter that on my computer. I quickly gave up on the spam filters built into Outlook and the other email clients I tried, but I found a free Bayesian filter that worked well for me: K9. Once I trained K9, it reached better than 99% accuracy, and I only needed to correct the classification of emails a few times a week. Unfortunately, the sheer volume of spam kept increasing, and it took longer and longer to download the first batch of emails in the morning, especially on Monday. That led me to do more filtering at the server.
Strategic Developer | Martin Heller | InfoWorld | Battling Spam | September 9, 2007 11:29 AM | By Martin Heller