Electronic Commerce Services (ECS) : An umbrella of services that would bring electronic mail up to the same level of acceptance that regular mail enjoys today. ECS includes a time and date stamp, return receipt, registered, certified, verification of sender and recipient, and archival services. Plans also call for creating public and private authentication keys to enable individuals to prove who they are when communicating on the Internet.

Electronic postmark : An electronic time and date stamp on electronic mail that will authenticate a document's existence at a particular point in time.

Embossing : The process by which part of the design of a stamp is 'raised'.

Engraving : The process of producing a stamp design from a metal or wood plate.

Entire : An intact piece of postal stationery, in contrast to a cut-out of the printed design.

Error : A stamp with something incorrect in its design, printing process or manufacture.

Essay : A stamp produced for trial or experimental purposes prior to the issue of the final agreed design.

Exploded : A stamp booklet is said to be "exploded" when it has been separated into its various components for show.

Express Mail : The Postal Service's premium delivery service, providing guaranteed overnight delivery for documents and packages.