imapext-2007
view docs/rfc/rfc2061.txt @ 0:ada5e610ab86
imap-2007e
| author | yuuji@gentei.org |
|---|---|
| date | Mon, 14 Sep 2009 15:17:45 +0900 |
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7 Network Working Group M. Crispin
8 Request for Comments: 2061 University of Washington
9 Category: Informational December 1996
12 IMAP4 COMPATIBILITY WITH IMAP2BIS
14 Status of this Memo
16 This memo provides information for the Internet community. This memo
17 does not specify an Internet standard of any kind. Distribution of
18 this memo is unlimited.
20 Introduction
22 The Internet Message Access Protocol (IMAP) has been through several
23 revisions and variants in its 10-year history. Many of these are
24 either extinct or extremely rare; in particular, several undocumented
25 variants and the variants described in RFC 1064, RFC 1176, and RFC
26 1203 fall into this category.
28 One variant, IMAP2bis, is at the time of this writing very common and
29 has been widely distributed with the Pine mailer. Unfortunately,
30 there is no definite document describing IMAP2bis. This document is
31 intended to be read along with RFC 1176 and the most recent IMAP4
32 specification (RFC 2060) to assist implementors in creating an IMAP4
33 implementation to interoperate with implementations that conform to
34 earlier specifications. Nothing in this document is required by the
35 IMAP4 specification; implementors must decide for themselves whether
36 they want their implementation to fail if it encounters old software.
38 At the time of this writing, IMAP4 has been updated from the version
39 described in RFC 1730. An implementor who wishes to interoperate
40 with both RFC 1730 and RFC 2060 should refer to both documents.
42 This information is not complete; it reflects current knowledge of
43 server and client implementations as well as "folklore" acquired in
44 the evolution of the protocol. It is NOT a description of how to
45 interoperate with all variants of IMAP, but rather with the old
46 variant that is most likely to be encountered. For detailed
47 information on interoperating with other old variants, refer to RFC
48 1732.
50 IMAP4 client interoperability with IMAP2bis servers
52 A quick way to check whether a server implementation supports the
53 IMAP4 specification is to try the CAPABILITY command. An OK response
54 will indicate which variant(s) of IMAP4 are supported by the server.
58 Crispin Informational [Page 1]
60 RFC 2061 IMAP4 Compatibility December 1996
63 If the client does not find any of its known variant in the response,
64 it should treat the server as IMAP2bis. A BAD response indicates an
65 IMAP2bis or older server.
67 Most IMAP4 facilities are in IMAP2bis. The following exceptions
68 exist:
70 CAPABILITY command
71 The absense of this command indicates IMAP2bis (or older).
73 AUTHENTICATE command.
74 Use the LOGIN command.
76 LSUB, SUBSCRIBE, and UNSUBSCRIBE commands
77 No direct functional equivalent. IMAP2bis had a concept
78 called "bboards" which is not in IMAP4. RFC 1176 supported
79 these with the BBOARD and FIND BBOARDS commands. IMAP2bis
80 augmented these with the FIND ALL.BBOARDS, SUBSCRIBE BBOARD,
81 and UNSUBSCRIBE BBOARD commands. It is recommended that
82 none of these commands be implemented in new software,
83 including servers that support old clients.
85 LIST command
86 Use the command FIND ALL.MAILBOXES, which has a similar syn-
87 tax and response to the FIND MAILBOXES command described in
88 RFC 1176. The FIND MAILBOXES command is unlikely to produce
89 useful information.
91 * in a sequence
92 Use the number of messages in the mailbox from the EXISTS
93 unsolicited response.
95 SEARCH extensions (character set, additional criteria)
96 Reformulate the search request using only the RFC 1176 syn-
97 tax. This may entail doing multiple searches to achieve the
98 desired results.
100 BODYSTRUCTURE fetch data item
101 Use the non-extensible BODY data item.
103 body sections HEADER, TEXT, MIME, HEADER.FIELDS, HEADER.FIELDS.NOT
104 Use body section numbers only.
106 BODY.PEEK[section]
107 Use BODY[section] and manually clear the \Seen flag as
108 necessary.
114 Crispin Informational [Page 2]
116 RFC 2061 IMAP4 Compatibility December 1996
119 FLAGS.SILENT, +FLAGS.SILENT, and -FLAGS.SILENT store data items
120 Use the corresponding non-SILENT versions and ignore the
121 untagged FETCH responses which come back.
123 UID fetch data item and the UID commands
124 No functional equivalent.
126 CLOSE command
127 No functional equivalent.
130 In IMAP2bis, the TRYCREATE special information token is sent as a
131 separate unsolicited OK response instead of inside the NO response.
133 IMAP2bis is ambiguous about whether or not flags or internal dates
134 are preserved on COPY. It is impossible to know what behavior is
135 supported by the server.
137 IMAP4 server interoperability with IMAP2bis clients
139 The only interoperability problem between an IMAP4 server and a
140 well-written IMAP2bis client is an incompatibility with the use of
141 "\" in quoted strings. This is best avoided by using literals
142 instead of quoted strings if "\" or <"> is embedded in the string.
144 Security Considerations
146 Security issues are not discussed in this memo.
148 Author's Address
150 Mark R. Crispin
151 Networks and Distributed Computing
152 University of Washington
153 4545 15th Aveneue NE
154 Seattle, WA 98105-4527
156 Phone: (206) 543-5762
157 EMail: MRC@CAC.Washington.EDU
170 Crispin Informational [Page 3]