Abstract: A system for authenticating electronic correspondence includes a sender, a recipient, and a central authorization service. The sender includes a correspondence client at which electronic correspondence is composed, a correspondence server for routing proposed correspondence, and a sender client. The recipient includes a correspondence client at which electronic correspondence is viewed, a correspondence server that delivers the correspondence to the correspondence client, and a recipient client. The central authorization service has a two-way communication link to each of the sender client and the recipient client. The sender client is configured to determine whether composed correspondence to be sent originates from at least one of an authorized server and an authorized domain before sending the correspondence and informs the central authorization service if a determination is made if the correspondence does not originate from an authorized server or an authorized domain.