Overview of Welcomed Correspondence Extensions to Mail Delivery and Mail Transfer Protocols
The goal of Welcomed Correspondence Extensions is to provide, in the simplest and least intrusive way possible (both programmatically and to the user), a method of avoiding unsolicited and unwanted email without drastically changing the infrastructure of the Internet's existing mail transports. This document describes a two-phase evolutionary approach in order to maintain compatibility with existing standard POP3/IMAP4 retrieval/delivery servers, SMTP mail transfer agents, and end-user mail clients.