Challenge / Response Interworking (CRI) Framework for Challenge / Response Email Systems
Crystal Ball Inc.
SolidMatrix Technologies
SMTP was designed simply to deliver email messages without authenticating sources or senders of email messages. In an affort to reduce spam on the Internet, Challenge/Response ('C/R') email systems were developed to provide a method for validating message origination for an intended recipient. This document defines a Challenge / Response Interworking ('CRI') protocol by proposing the use of SMTP extensions and MIME headers for interoperability of C/R systems. This document also defines a set of guidelines for continued use with existing non-CRI mail systems and clients.