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