From TechRepublic:
A new Web site aims to help determine whether a specific computer has been sending legitimate e-mail or spam.
The TrustedSource Web site uses data from reputation filters, which are billed as the next big thing in e-mail security. Makers of spam-fighting tools collect data on e-mail senders and use that to assign “reputations” to e-mail sending computers and Internet domains. Those who send a lot of spam get a negative rating and their messages are more likely to be filtered out.