Patent ID: 8396926

Claim:
A method of registering an electronic-mail (e-mail) sender for the purpose of sending e-mail messages to an e-mail recipient, the method comprising: receiving a challenge message in response to an e-mail message sent by the email sender, wherein the challenge message includes a machine answerable question; processing the challenge message to determine that the message is a challenge message sent for the purpose of authorizing delivery of e-mail messages, wherein processing the challenge message includes identifying an indicator that the message is a challenge message; parsing the message to locate the machine answerable question in the challenge message; analyzing the question to determine a valid response to the challenge message, wherein a nontrivial amount of resources are required to determine the valid response; and sending the valid response, wherein the valid response includes a correct answer to the machine answerable question, the machine answerable question being automatically analyzed without human intervention, wherein an independent third-party auditor verifies validity of the response and sends a report to the e-mail recipient indicating the validity of the response, and wherein receipt of the report indicating the valid response results in the e-mail sender being registered as a valid e-mail sender whereby subsequent e-mail messages sent by the registered and valid e-mail sender will not require sending a valid response to a challenge message.