Mailwash is a great free program, as is Mailblocks. (The free versions will only handle transfers from a single account.)
Mailwash is nice, because you can "bounce" mail back to the spammers. In some cases, this will reduce the amount of spam, since some will delete "bounced" email from their lists.
Mailblocks puts all questionable mail into a "pending" file and sends an email to the sender, asking any person who may have sent a legitimate email to perform a simple task that a computer cannot do. In 3 days, the computer deletes all unanswered email.
Spam is a real problem for anyone using an email that is published on a website. Harvesters scan the internet and gathers all names with an @ sign. Guess what they do with those names! I still get over 1000 email a day, in spite of Ted's blocking many. Most are viruses! In a three day period of time, these junk email take up 50 - 70 meg of storage on the Mailblocks server.
Interestingly, Hotmail, Yahoo and other popular email programs, will block nearly all virus attachments before the user gets them.
"Do or do not. there is no try!"