From Pro Softnet:
BSpam automatically blocks unwanted spam mails. There is absolutely no configuration required. BSpam blocks e-mails with a little help from you that helps everyone almost real time. BSpam can be installed as a plug-in to your existing Outlook Express or Microsoft Outlook. BSpam users can report a particular e-mail as spam, and once e-mail is reported as spam by one user, it is blocked from reaching the inbox of others thus benefiting all users of BSpam. BSpam is a community where BSpam users report spam mails for the benefit of other BSpam users. It automatically identifies and moves spam mails to a separate folder till you decide to manually delete those mails.