Patent ID: 8126971

Claim:
A method for determining whether an e-mail originates from a sender who is authorized by an address provider to send the e-mail to an intended recipient's e-mail address, the method comprising: using at least one computer to perform the steps of: receiving an e-mail directed to an intended recipient's e-mail address; determining a first identifier encoded in the e-mail identifying a sender of the e-mail; determining a second identifier encoded in the e-mail that is distinct from the first identifier and from any e-mail address for the recipient, the second identifier identifying an address provider distinct from the sender and from the intended recipient as an entity from which the sender obtained the intended recipient's e-mail address; in response to determining the second identifier, querying an authentication server to determine whether the sender is authorized by the address provider to obtain the intended recipient's e-mail address used for sending the e-mail to the intended recipient; receiving a response from the authentication server; delivering the e-mail to the intended recipient if the response indicates that the sender is authorized by the address provider to obtain the intended recipient's e-mail address used for sending the e-mail to the intended recipient; and preventing normal delivery of the e-mail to the intended recipient if the response indicates that the sender is not authorized by the address provider to obtain the intended recipient's e-mail address used for sending the e-mail to the intended recipient.