RFC 2061 (rfc2061) - Page 1 of 3

IMAP4 Compatibility with IMAP2bis

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Network Working Group                                         M. Crispin
Request for Comments: 2061                      University of Washington
Category: Informational                                    December 1996


                   IMAP4 COMPATIBILITY WITH IMAP2BIS

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Introduction

   The Internet Message Access Protocol (IMAP) has been through several
   revisions and variants in its 10-year history.  Many of these are
   either extinct or extremely rare; in particular, several undocumented
   variants and the variants described in RFC 1064, RFC 1176, and RFC
   1203 fall into this category.

   One variant, IMAP2bis, is at the time of this writing very common and
   has been widely distributed with the Pine mailer.  Unfortunately,
   there is no definite document describing IMAP2bis.  This document is
   intended to be read along with RFC 1176 and the most recent IMAP4
   specification (RFC 2060) to assist implementors in creating an IMAP4
   implementation to interoperate with implementations that conform to
   earlier specifications.  Nothing in this document is required by the
   IMAP4 specification; implementors must decide for themselves whether
   they want their implementation to fail if it encounters old software.

   At the time of this writing, IMAP4 has been updated from the version
   described in RFC 1730.  An implementor who wishes to interoperate
   with both RFC 1730 and RFC 2060 should refer to both documents.

   This information is not complete; it reflects current knowledge of
   server and client implementations as well as "folklore" acquired in
   the evolution of the protocol.  It is NOT a description of how to
   interoperate with all variants of IMAP, but rather with the old
   variant that is most likely to be encountered.  For detailed
   information on interoperating with other old variants, refer to RFC
   1732.

IMAP4 client interoperability with IMAP2bis servers

   A quick way to check whether a server implementation supports the
   IMAP4 specification is to try the CAPABILITY command.  An OK response
   will indicate which variant(s) of IMAP4 are supported by the server.



Crispin                      Informational
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