Patent ID: 8015607

Claim:
A computer-implemented method of processing electronic messages, the method comprising: receiving a first electronic message that is associated with a stamp and that is addressed to a recipient, wherein associating the stamp with the first electronic message imposes an additional transaction cost on a sender of the first electronic message and appends, to the first electronic message, non-display stamp information that enables determination of whether the stamp associated with the first electronic message is valid; receiving a second electronic message that is not associated with a stamp and that is addressed to the recipient, wherein sending the second electronic message that is not associated with a stamp does not impose the additional transaction cost on a sender of the second electronic message; identifying the non-display stamp information appended to the first electronic message; determining whether the stamp associated with the first electronic message is valid based on the identified non-display stamp information; in response to a determination that the stamp associated with the first electronic message is valid, causing a user interface that is configured to display representations of electronic messages received by the recipient to display a first representation of the first electronic message in a first manner; determining whether the second electronic message is associated with a stamp; and in response to a determination that the second electronic message is not associated with a stamp, causing the user interface to display a second representation of the second electronic message in a second manner that is visually distinct from the first manner in which the first representation of the first electronic message is displayed in the user interface.