Browse Prior Art Database

IMAP4 Compatibility with IMAP2 and IMAP2bis (RFC1732)

IP.com Disclosure Number: IPCOM000003981D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 4 page(s) / 9K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

M. Crispin: AUTHOR

Abstract

This is a summary of hints and recommendations to enable an IMAP4 implementation to interoperate with implementations that conform to earlier specifications. None of these hints and recommendations are required by the IMAP4 specification; implementors must decide for themselves whether they want their implementation to fail if it encounters old software.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 32% of the total text.

Network Working Group M. Crispin

Request for Comments: 1732 University of Washington

Category: Informational December 1994

IMAP4 COMPATIBILITY WITH IMAP2 AND 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

This is a summary of hints and recommendations to enable an IMAP4

implementation to interoperate with implementations that conform to

earlier specifications. None of these hints and recommendations are

required by the IMAP4 specification; implementors must decide for

themselves whether they want their implementation to fail if it

encounters old software.

IMAP4 has been designed to be upwards compatible with earlier

specifications. For the most part, IMAP4 facilities that were not in

earlier specifications should be invisible to clients unless the

client asks for the facility.

In some cases, older servers may support some of the capabilities

listed as being "new in IMAP4" as experimental extensions to the

IMAP2 protocol described in RFC 1176.

This information may not be complete; it reflects current knowledge

of server and client implementations as well as "folklore" acquired

in the evolution of the protocol.

IMAP4 client interoperability with old servers

In general, a client should be able to discover whether an IMAP2

server supports a facility by trial-and-error; if an attempt to use a

facility generates a BAD response, the client can assume that the

server does not support the facility.

A quick way to check whether a server implementation supports the

IMAP4 specification is to try the CAPABILITY command. An OK response

that includes the IMAP4 capability value indicates a server that

supports IMAP4; a BAD response or one without the IMAP4 capability

value indicates an older server.

The following is a list of facilities that are only in IMAP4, and

suggestions for how new clients might interoperate with old servers:

CAPABILITY command

A BAD response to this command indicates that the server

implements IMAP2 (or IMAP2bis) and not IMAP4.

AUTHENTICATE command.

Use the LOGIN command.

LSUB and LIST commands

Try the RFC 1176 FIND command.

* in a sequence

Use the number of messages in the mailbox from the EXISTS

unsolicited response.

SEARCH extensions (character set, additional criteria)

...