In order to help against SPAM mail, we have installed SpamAssassin (Tags known SPAM mail), MailScanner (an email virus scanner), Clam AntiVirus (another Virus Scanner for your emails). Emails that are tagged as SPAM mail will show "{Spam?}" or "{HighScoreSpam?}", and emails with a known virus will be tagged as "{Virus?}" in the subject line.
For "Mail Filter" on your PC, check out MailFrontier, we have just started using it and so far it seems to be great at blocking the SPAM mail. Below is a list of more SPAM mail filters that may be of help.
Here is another new one to try and it is free, but they would like a donation for there efforts, http://spambayes.sourceforge.net/ I hear that it is working very well for others.