Challenge / Response Interworking (CRI) Framework for Challenge / Response Email Systems

Document Type Expired Internet-Draft (asrg RG)
Authors Eric Dean  , Yakov Shafranovich 
Last updated 2003-09-23
Stream Internet Research Task Force (IRTF)
Expired & archived
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


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.


Eric Dean (
Yakov Shafranovich (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)