Patent ID: 7739338

Claim:
A method comprising: passing a first email message having a header, the header including a first from-email address value in a from-email address field and a to-email address value in a to-email address field, the email message also containing a subscriber-created first sender-validation key value located in the to-email address field of the header of the email message, from a first email-client application program located in a first sender computer system to a second application program that includes a sender-validation-engine and that is also located in the first sender computer system, wherein the first from-email-address value includes a local part, a first domain name and high-level extension; using the second application program that includes the sender-validation-engine, encoding the first email message to form a first encoded email message, wherein the encoding adds tags to each of a plurality of parts of the email message; transmitting the encoded email message from a first computer to a second computer; decoding the encoded email message to reveal an un-encoded version of the email message; parsing the un-encoded email message to obtain information including the first sender-validation key value and the from-email address value; and checking whether the first sender-validation key value is valid for the first to-email address value and whether the email was sent from the first from-email address, and if so then forwarding the first email to the first to-email address.