Patent ID: 7644274

Claim:
A computer-implemented method for preventing receipt by receivers of unwanted electronic mail messages (email) sent by senders in a communication system, comprising the steps of: determining whether email to a particular receiver comprises valid message authentication code (MAC) information; filtering out at a gateway of the communication system email directed to the particular receiver that does not comprise valid MAC information; providing the particular receiver with email directed to the particular receiver that comprises valid MAC information; determining if a particular sender is a registered sender of email to the particular receiver, wherein the particular sender becomes a registered sender by satisfying a requirement; and registering the particular sender when the particular sender is determined not to be a registered sender of email to the particular receiver; wherein the step of registering the particular sender comprises the steps of: establishing by the particular sender a cookie which indicates to the particular receiver whether the particular sender has satisfied the requirement to allow the particular sender to become a registered sender to the particular receiver; establishing an address related to an address associated with the particular receiver which will inform the particular sender that the particular receiver desires that the particular sender be able to send email to the particular receiver; and establishing by the particular receiver a key which is forwarded to the particular sender by the particular receiver to inform the particular sender that the particular sender is authorized to send email to the particular receiver and is now a registered sender and for use by the particular sender whenever the particular sender wishes to send email to the particular receiver; wherein said step of establishing the address comprises generating a pseudorandom function with a keyed hash function using an input number comprising a unique serial number for use in generating an identifier for email between the particular sender to the particular receiver; wherein each of said steps is performed by one or more computers.