Messaging stamp authority

A system comprising:

• at least one computer;
• and
• a computer-readable medium coupled to the at least one computer having instructions stored thereon which, when executed by the at least one computer, cause the at least one computer to perform operations 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.

A computer-implemented method of processing electronic messages using a stamp authority, the method comprising:

• receiving an electronic message that was sent by a sender, that is addressed to a recipient, and that is associated with non-display stamp information, the non-display stamp information being generated by a stamp authority system that is different from a transmitting system from which the sender originated the electronic message and the stamp authority system imposing an additional transaction cost, borne by the sender, for generation of the non-display stamp information;
• identifying the non-display stamp information associated with the electronic message;
• determining whether the non-display stamp information associated with the electronic message represents a valid stamp that has been associated with the electronic message;
• displaying, regardless of the determination, a representation of the electronic message in a user interface that is configured to display representations of electronic messages;
• in response to a determination that the non-display stamp information associated with the electronic message represents a valid stamp that has been associated with the electronic message, handling the electronic message in a first manner;
• and
• in response to a determination that the non-display stamp information associated with the electronic message does not represent a valid stamp that has been associated with the electronic message, handling the electronic message in a second manner that is distinct from the first manner.