The origin address of an e-mail message is validated to enable blocking of e-mail from spam e-mail sources, by preparing, in response to the receipt of a predetermined e-mail message from an unverified source address, a data key encoding information reflective of the predetermined e-mail message. This...http://www.google.com/patents/US7483951?utm_source=gb-gplus-sharePatent US7483951 - Method and system for selectively blocking delivery of electronic mail
