Dear Postal Customer:
The United States Postal Service is chartered by the federal government as the sole carrier of routine correspondence within the United States. This position has been uniformly upheld by the Courts, ruling that private carriers may not offer general correspondence service. Accordingly, we at the USPS have recognized our responsibility for all such correspondence carried by various providers utilizing the Internet. We have determined that it is within the scope of our charter to regulate messaging via electronic mail; the Postal Service has primary authority over correspondence, regardless of the medium, whether paper or electronic.
Therefore, we have reviewed your electronic postal usage for the past year and have billed you accordingly for the postage due.
While it was intended as humour, enough people took it seriously that he may have inadvertently triggered one iteration of the email postage urban legend.