How do computers identify junk mail?
The science behind the service that sifts through your spam. Junk mail is detected by scanning the message for common warning signs. Was the message sent from a blacklisted network? Have the headers been tampered with to hide the sender? Does the subject line use all capital letters? All these factors are added together to give a weighted score, and anything over a certain number is deemed to be spam. If you manually mark an email as spam, it also refines the scoring system for future emails.