My personal email address got picked up in a spammer distribution list at some point and over the course of 5 years got to a point where about 98% of the inbound email was spam.  Outlook was filter about 2/3 of it but I fixed it for good by moving my POP services from a mom&pop hoster to godaddy.  About 99% of the spam stopped immediately.  Godaddy must have a well managed spam filter (probably uses a blacklist to filter out spammers SMTP servers).

If your account is on hotmail or gmail or any other web-base email system then I suppose you're SOL.  If it's a private email address (ie. your own domain) then you could look a moving to another hoster that stops spam at the gateway.