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+Network Working Group                                        A. Melnikov
+Request for Comments: 3691                                    Isode Ltd.
+Category: Standards Track                                  February 2004
+
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+        Internet Message Access Protocol (IMAP) UNSELECT command
+
+Status of this Memo
+
+   This document specifies an Internet standards track protocol for the
+   Internet community, and requests discussion and suggestions for
+   improvements.  Please refer to the current edition of the "Internet
+   Official Protocol Standards" (STD 1) for the standardization state
+   and status of this protocol.  Distribution of this memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2004).  All Rights Reserved.
+
+Abstract
+
+   This document defines an UNSELECT command that can be used to close
+   the current mailbox in an Internet Message Access Protocol - version
+   4 (IMAP4) session without expunging it.  Certain types of IMAP
+   clients need to release resources associated with the selected
+   mailbox without selecting a different mailbox.  While IMAP4 provides
+   this functionality (via a SELECT command with a nonexistent mailbox
+   name or reselecting the same mailbox with EXAMINE command), a more
+   clean solution is desirable.
+
+Table of Contents
+
+   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
+   2.  UNSELECT command . . . . . . . . . . . . . . . . . . . . . . .  2
+   3.  Security Considerations. . . . . . . . . . . . . . . . . . . .  3
+   4.  Formal Syntax. . . . . . . . . . . . . . . . . . . . . . . . .  3
+   5.  IANA Considerations. . . . . . . . . . . . . . . . . . . . . .  3
+   6.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . .  3
+   7.  Normative References . . . . . . . . . . . . . . . . . . . . .  4
+   8.  Author's Address . . . . . . . . . . . . . . . . . . . . . . .  4
+   9.  Full Copyright Statement . . . . . . . . . . . . . . . . . . .  5
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+Melnikov                    Standards Track                     [Page 1]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
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+1.  Introduction
+
+   Certain types of IMAP clients need to release resources associated
+   with the selected mailbox without selecting a different mailbox.
+   While [IMAP4] provides this functionality (via a SELECT command with
+   a nonexistent mailbox name or reselecting the same mailbox with
+   EXAMINE command), a more clean solution is desirable.
+
+   [IMAP4] defines the CLOSE command that closes the selected mailbox as
+   well as permanently removes all messages with the \Deleted flag set.
+
+   However [IMAP4] lacks a command that simply closes the mailbox
+   without expunging it.  This document defines the UNSELECT command for
+   this purpose.
+
+   A server which supports this extension indicates this with a
+   capability name of "UNSELECT".
+
+   "C:" and "S:" in examples show lines sent by the client and server
+   respectively.
+
+   The keywords "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" in
+   this document when typed in uppercase are to be interpreted as
+   defined in "Key words for use in RFCs to Indicate Requirement Levels"
+   [KEYWORDS].
+
+2.  UNSELECT Command
+
+   Arguments:  none
+
+   Responses:  no specific responses for this command
+
+   Result:     OK - unselect completed, now in authenticated state
+               BAD - no mailbox selected, or argument supplied but
+                     none permitted
+
+      The UNSELECT command frees server's resources associated with the
+      selected mailbox and returns the server to the authenticated
+      state.  This command performs the same actions as CLOSE, except
+      that no messages are permanently removed from the currently
+      selected mailbox.
+
+   Example:    C: A341 UNSELECT
+               S: A341 OK Unselect completed
+
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+
+Melnikov                    Standards Track                     [Page 2]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
+
+3.  Security Considerations
+
+   It is believed that this extension doesn't raise any additional
+   security concerns not already discussed in [IMAP4].
+
+4.  Formal Syntax
+
+   The following syntax specification uses the Augmented Backus-Naur
+   Form (ABNF) notation as specified in [ABNF].  Non-terminals
+   referenced but not defined below are as defined by [IMAP4].
+
+   Except as noted otherwise, all alphabetic characters are case-
+   insensitive.  The use of upper or lower case characters to define
+   token strings is for editorial clarity only.  Implementations MUST
+   accept these strings in a case-insensitive fashion.
+
+   command-select  /= "UNSELECT"
+
+5.  IANA Considerations
+
+   IMAP4 capabilities are registered by publishing a standards track or
+   IESG approved experimental RFC.  The registry is currently located
+   at:
+
+      http://www.iana.org/assignments/imap4-capabilities
+
+   This document defines the UNSELECT IMAP capabilities.  IANA has added
+   this capability to the registry.
+
+6.  Acknowledgments
+
+   UNSELECT command was originally implemented by Tim Showalter in Cyrus
+   IMAP server.
+
+   Also, the author of the document would like to thank Vladimir Butenko
+   and Mark Crispin for reminding that UNSELECT has to be documented.
+   Also thanks to Simon Josefsson for pointing out that there are
+   multiple ways to implement UNSELECT.
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+Melnikov                    Standards Track                     [Page 3]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
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+7.  Normative References
+
+   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+   [IMAP4]    Crispin, M., "Internet Message Access Protocol - Version
+              4rev1", RFC 3501, March 2003.
+
+   [ABNF]     Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
+              Specifications: ABNF", RFC 2234, November 1997.
+
+8.  Author's Address
+
+   Alexey Melnikov
+   Isode Limited
+   5 Castle Business Village
+   Hampton, Middlesex TW12 2BX
+
+   EMail: Alexey.Melnikov@isode.com
+   URI: http://www.melnikov.ca/
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+Melnikov                    Standards Track                     [Page 4]
+
+RFC 3691                 IMAP UNSELECT command             February 2004
+
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+9.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2004).  This document is subject
+   to the rights, licenses and restrictions contained in BCP 78 and
+   except as set forth therein, the authors retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
+   REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
+   INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed
+   to pertain to the implementation or use of the technology
+   described in this document or the extent to which any license
+   under such rights might or might not be available; nor does it
+   represent that it has made any independent effort to identify any
+   such rights.  Information on the procedures with respect to
+   rights in RFC documents can be found in BCP 78 and BCP 79.
+
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+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use
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+   specification can be obtained from the IETF on-line IPR repository
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+
+   The IETF invites any interested party to bring to its attention
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+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
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+Melnikov                    Standards Track                     [Page 5]
+