7Network Working Group A. Melnikov
8Request for Comments: 3691 Isode Ltd.
9Category: Standards Track February 2004
12 Internet Message Access Protocol (IMAP) UNSELECT command
16 This document specifies an Internet standards track protocol for the
17 Internet community, and requests discussion and suggestions for
18 improvements. Please refer to the current edition of the "Internet
19 Official Protocol Standards" (STD 1) for the standardization state
20 and status of this protocol. Distribution of this memo is unlimited.
24 Copyright (C) The Internet Society (2004). All Rights Reserved.
28 This document defines an UNSELECT command that can be used to close
29 the current mailbox in an Internet Message Access Protocol - version
30 4 (IMAP4) session without expunging it. Certain types of IMAP
31 clients need to release resources associated with the selected
32 mailbox without selecting a different mailbox. While IMAP4 provides
33 this functionality (via a SELECT command with a nonexistent mailbox
34 name or reselecting the same mailbox with EXAMINE command), a more
35 clean solution is desirable.
39 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
40 2. UNSELECT command . . . . . . . . . . . . . . . . . . . . . . . 2
41 3. Security Considerations. . . . . . . . . . . . . . . . . . . . 3
42 4. Formal Syntax. . . . . . . . . . . . . . . . . . . . . . . . . 3
43 5. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 3
44 6. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 3
45 7. Normative References . . . . . . . . . . . . . . . . . . . . . 4
46 8. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 4
47 9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 5
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60RFC 3691 IMAP UNSELECT command February 2004
65 Certain types of IMAP clients need to release resources associated
66 with the selected mailbox without selecting a different mailbox.
67 While [IMAP4] provides this functionality (via a SELECT command with
68 a nonexistent mailbox name or reselecting the same mailbox with
69 EXAMINE command), a more clean solution is desirable.
71 [IMAP4] defines the CLOSE command that closes the selected mailbox as
72 well as permanently removes all messages with the \Deleted flag set.
74 However [IMAP4] lacks a command that simply closes the mailbox
75 without expunging it. This document defines the UNSELECT command for
78 A server which supports this extension indicates this with a
79 capability name of "UNSELECT".
81 "C:" and "S:" in examples show lines sent by the client and server
84 The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in
85 this document when typed in uppercase are to be interpreted as
86 defined in "Key words for use in RFCs to Indicate Requirement Levels"
93 Responses: no specific responses for this command
95 Result: OK - unselect completed, now in authenticated state
96 BAD - no mailbox selected, or argument supplied but
99 The UNSELECT command frees server's resources associated with the
100 selected mailbox and returns the server to the authenticated
101 state. This command performs the same actions as CLOSE, except
102 that no messages are permanently removed from the currently
105 Example: C: A341 UNSELECT
106 S: A341 OK Unselect completed
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116RFC 3691 IMAP UNSELECT command February 2004
1193. Security Considerations
121 It is believed that this extension doesn't raise any additional
122 security concerns not already discussed in [IMAP4].
126 The following syntax specification uses the Augmented Backus-Naur
127 Form (ABNF) notation as specified in [ABNF]. Non-terminals
128 referenced but not defined below are as defined by [IMAP4].
130 Except as noted otherwise, all alphabetic characters are case-
131 insensitive. The use of upper or lower case characters to define
132 token strings is for editorial clarity only. Implementations MUST
133 accept these strings in a case-insensitive fashion.
1375. IANA Considerations
139 IMAP4 capabilities are registered by publishing a standards track or
140 IESG approved experimental RFC. The registry is currently located
143 http://www.iana.org/assignments/imap4-capabilities
145 This document defines the UNSELECT IMAP capabilities. IANA has added
146 this capability to the registry.
150 UNSELECT command was originally implemented by Tim Showalter in Cyrus
153 Also, the author of the document would like to thank Vladimir Butenko
154 and Mark Crispin for reminding that UNSELECT has to be documented.
155 Also thanks to Simon Josefsson for pointing out that there are
156 multiple ways to implement UNSELECT.
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172RFC 3691 IMAP UNSELECT command February 2004
1757. Normative References
177 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
178 Requirement Levels", BCP 14, RFC 2119, March 1997.
180 [IMAP4] Crispin, M., "Internet Message Access Protocol - Version
181 4rev1", RFC 3501, March 2003.
183 [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
184 Specifications: ABNF", RFC 2234, November 1997.
190 5 Castle Business Village
191 Hampton, Middlesex TW12 2BX
193 EMail: Alexey.Melnikov@isode.com
194 URI: http://www.melnikov.ca/
226Melnikov Standards Track [Page 4]
228RFC 3691 IMAP UNSELECT command February 2004
2319. Full Copyright Statement
233 Copyright (C) The Internet Society (2004). This document is subject
234 to the rights, licenses and restrictions contained in BCP 78 and
235 except as set forth therein, the authors retain all their rights.
237 This document and the information contained herein are provided on an
238 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
239 REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
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282Melnikov Standards Track [Page 5]