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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 RFC 5464

Network Working Group                                           C. Daboo
Internet-Draft                                                     Apple
Intended status: Standards Track                       February 25, 2007
Expires: August 29, 2007


                        IMAP METADATA Extension
                    draft-daboo-imap-annotatemore-11

Status of this Memo

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   This Internet-Draft will expire on August 29, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The METADATA extension to the Internet Message Access Protocol
   permits clients and servers to maintain "annotations" or "meta data"
   on IMAP servers.  It is possible to have annotations on a per-mailbox
   basis or on the server as a whole.  For example, this would allow
   comments about the purpose of a particular mailbox to be "attached"
   to that mailbox, or a "message of the day" containing server status
   information to be made available to anyone logging in to the server.




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Change History (to be removed prior to publication as an RFC)

   Changes from -10 to -11:
   1.   Added new paragraph to indicate that values may be read-only or
        computed.
   2.   /admin server annotation value now must be a URI.
   3.   Clarified that SORT and THREAD extensions are not required.
   4.   Fixed use of undefined entries in some examples.
   5.   Fixed many examples.
   6.   Added IANA registration for LIST-EXTENDED items.
   7.   Added match type and collation identifier to the LIST-EXTENDED
        selection option.
   8.   Made support for IMAP-I18N a requirement.
   9.   Minor text clarifications applied.
   10.  Remove mailbox list set atomicity requirement.
   11.  Clarified that annotations can only be set on mailboxes that
        actually exist.

   Changes from -09 to -10:
   1.  Updated to rfc 4466 reference.
   2.  Reworded data model description.
   3.  Reworked LIST-EXTENDED so that responses have metadata items
       after the mailbox info.
   4.  Various spelling fixes.

   Changes from -08 to -09:
   1.  Remove content-language attribute and reference.
   2.  Changed capability and command names.
   3.  Revised abstract.

   Changes from -07 to -08:
   1.   Changed 'string' formal syntax to 'list-mailbox' and 'astring'
        for entry/attribute names.
   2.   Updated examples to match new astring syntax.
   3.   Changed CAPABILITY name due to incompatible syntax change.
   4.   Removed content-type attribute.
   5.   Added Content-type to IANA registration for entries.
   6.   Removed vendor attributes.
   7.   Fixed examples in section 3.3 for multi-mailbox and multi-entry
        cases.
   8.   Removed wildcards for attributes.
   9.   Entry/attributes can now only be ASCII.
   10.  Tied up text wrt storing/fetching.
   11.  Added Conventions section
   12.  Entry/attributes MUST NOT contain consecutive or trailing '/' or
        '.'.





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   13.  Changed to use IMAP ABNF extensions document for some formal
        syntax items.

   Changes from -06 to -07:
   1.  Reworded /checkperiod item.
   2.  Clarified unsolicited response behavior.

   Changes from -05 to -06:
   1.  Removed 'modifiedsince' attribute as there is currently no use
       for it.
   2.  Added content-language attribute.
   3.  Changed access to allow .priv and .shared on any mailbox returned
       by LIST/LSUB.
   4.  Added IANA registrations for items defined in this document.
   5.  Added latest IPR statement.
   6.  Updated references.

   Changes from -04 to -05:
   1.  Fix for valid IMAP state of commands.
   2.  Fix formatting, ID nits etc.

   Changes from -03 to -04:
   1.  Allow retrieval of shared annotations for READ-ONLY mailbox.
   2.  Clarification of annotation loss on implicit removal of \Noselect
       mailboxes.
   3.  Now requires roll-back of all changes to matching mailboxes if
       there is a partial failure in SETANNOTATION.

   Changes from -02 to -03:
   1.  Reworked entry naming scheme to split out mailbox name and use
       empty string for server items.

   Changes from -01 to -02:
   1.  SETANNOTATION lists use (..).
   2.  Explicitly state behavior of unsolicited responses.
   3.  Adding SHOULD behavior for rename/delete of mailboxes.
   4.  Added statement about supporting annotations on \Noselect
       mailboxes.
   5.  Cleaned up formal syntax to use IMAP string type for entry and
       attributes, with requirements on how the string is formatted.
   6.  Use of ACAP vendor subtree registry for vendor tokens.

   Changes from -00 to -01:
   1.  Multiple entry-att responses are now simply delimited by spaces
       in line with ANNOTATE spec.  Adjusted examples to match.
   2.  Fixed entry-list formal syntax item to account for unsolicited
       parenthesized list of entries.




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   3.  Removed setentries formal syntax item for simplicity since its
       only used once.
   4.  Removed reference to 'message annotation' in section 5.1.
   5.  Changed formal syntax to restrict top level entries to /server
       and /mailbox/{...} only.  Re-arranged entry names section to
       account for this change.
   6.  Added comment and example for ANNOTATION response to allow
       servers to return separate responses for each entry if desired.











































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Table of Contents

   1.  Introduction and Overview  . . . . . . . . . . . . . . . . . .  6
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  6
   3.  Data Model . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Namespace of entries and attributes  . . . . . . . . . . .  7
       3.2.1.  Entry Names  . . . . . . . . . . . . . . . . . . . . .  8
       3.2.2.  Attribute Names  . . . . . . . . . . . . . . . . . . . 10
     3.3.  Private versus Shared and Access Control . . . . . . . . . 10
   4.  IMAP Protocol Changes  . . . . . . . . . . . . . . . . . . . . 11
     4.1.  General Considerations . . . . . . . . . . . . . . . . . . 11
     4.2.  GETMETADATA Command  . . . . . . . . . . . . . . . . . . . 12
     4.3.  Extended LIST Command Extensions . . . . . . . . . . . . . 13
       4.3.1.  Unsolicited LIST response  . . . . . . . . . . . . . . 18
     4.4.  SETMETADATA Command  . . . . . . . . . . . . . . . . . . . 18
     4.5.  METADATA Response  . . . . . . . . . . . . . . . . . . . . 21
       4.5.1.  METADATA response with attributes and values . . . . . 21
       4.5.2.  Unsolicited METADATA response without attributes
               and values . . . . . . . . . . . . . . . . . . . . . . 22
   5.  Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . . . 23
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 25
     6.1.  Entry and Attribute Registration Template  . . . . . . . . 26
     6.2.  Server Entry Registrations . . . . . . . . . . . . . . . . 26
       6.2.1.  /comment . . . . . . . . . . . . . . . . . . . . . . . 27
       6.2.2.  /motd  . . . . . . . . . . . . . . . . . . . . . . . . 27
       6.2.3.  /admin . . . . . . . . . . . . . . . . . . . . . . . . 28
     6.3.  Mailbox Entry Registrations  . . . . . . . . . . . . . . . 28
       6.3.1.  /comment . . . . . . . . . . . . . . . . . . . . . . . 28
       6.3.2.  /sort  . . . . . . . . . . . . . . . . . . . . . . . . 29
       6.3.3.  /thread  . . . . . . . . . . . . . . . . . . . . . . . 29
       6.3.4.  /check . . . . . . . . . . . . . . . . . . . . . . . . 30
       6.3.5.  /checkperiod . . . . . . . . . . . . . . . . . . . . . 30
     6.4.  Attribute Registrations  . . . . . . . . . . . . . . . . . 30
       6.4.1.  value  . . . . . . . . . . . . . . . . . . . . . . . . 31
       6.4.2.  size . . . . . . . . . . . . . . . . . . . . . . . . . 31
     6.5.  LIST-EXTENDED Registration . . . . . . . . . . . . . . . . 31
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 33
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 33
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 33
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 34
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 34
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 34
   Intellectual Property and Copyright Statements . . . . . . . . . . 35







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1.  Introduction and Overview

   The METADATA extension is present in any IMAP [RFC3501]
   implementation which returns "METADATA" as one of the supported
   capabilities in the CAPABILITY command response.  The "LIST-EXTENDED"
   [I-D.ietf-imapext-list-extensions] extension MUST also be present.

   The goal of METADATA is to provide a means for clients to set and
   retrieve "annotations" or "meta data" on an IMAP server.  The
   annotations can be associated with specific mailboxes or the server
   as a whole.

   The METADATA extension adds two new commands and one new untagged
   response to the IMAP base protocol.  It adds one new LIST-EXTENDED
   "selection" [I-D.ietf-imapext-list-extensions] option type and one
   new LIST-EXTENDED "return" [I-D.ietf-imapext-list-extensions] option
   type.

   This extension makes the following changes to the IMAP protocol:

   o  adds a new SETMETADATA command
   o  adds a new GETMETADATA command
   o  adds a new METADATA untagged response
   o  adds a new METADATA response code
   o  adds a new METADATA LIST-EXTENDED selection option type
   o  adds a new METADATA LIST-EXTENDED return option type

   The data model used in METADATA is exactly the same as that used in
   the ANNOTATE [I-D.ietf-imapext-annotate] extension to IMAP.  This is
   modeled after that of the Application Configuration Access Protocol
   [RFC2244] with the exception of inheritance which is not deemed
   necessary here.

   Text comparisons may be done as part of the GETMETADATA or LIST-
   EXTENDED commands.  As a result, support for the COMPARATOR
   [I-D.ietf-imapext-i18n] extension is REQUIRED.

   The rest of this document describes the data model and protocol
   changes more rigorously.


2.  Conventions Used in This Document

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this



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   document are to be interpreted as described in [RFC2119].

   Whitespace and line breaks have been added to the examples in this
   document to promote readability.


3.  Data Model

3.1.  Overview

   Mailboxes or the server as a whole may have zero or more annotations
   associated with them.  An annotation contains a uniquely named entry
   with a set of uniquely named attributes, each of which has a value.
   Annotations can be added to mailboxes when a mailbox name is provided
   as the first argument to the new command, or to the server as a whole
   when the empty string is provided as the first argument to the new
   command.

   For example, a general comment being added to a mailbox may have an
   entry name of "/comment".  This entry could include named attributes
   such as "value" and "size" etc to represent properties and data
   associated with the entry.

   The protocol changes to IMAP described below allow a client to access
   or change the values of any attributes in any annotation entry,
   assuming it has sufficient access rights to do so.

3.2.  Namespace of entries and attributes

   Each annotation is an entry that has a hierarchical name, with each
   component of the name separated by a slash ("/").  An entry name MUST
   NOT contain two consecutive "/" characters and MUST NOT end with a
   "/" character.

   Each entry is made up of a set of attributes.  Each attribute has a
   hierarchical name, with each component of the name separated by a
   period (".").  An attribute name MUST NOT contain two consecutive "."
   characters and MUST NOT end with a "." character.

   The value of an attribute is NIL (has no value), or a string of zero
   or more octets.

   Entry and attribute names MUST NOT contain asterisk ("*") or percent
   ("%") characters and MUST NOT contain non-ASCII characters or the NUL
   octet.  Invalid entry or attribute names result in a BAD response in
   any IMAP commands where they are used.

   Attribute names MUST NOT contain any hierarchical components with the



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   names "priv" or "shared" as those have special meaning (see
   Section 3.3).

   Entry and attribute names are case-sensitive.

   Use of control or punctuation characters in entry and attribute names
   is strongly discouraged.

   This specification defines an initial set of entry and attribute
   names available for use with mailbox and server annotations.  In
   addition an extension mechanism is described to allow additional
   names to be added for extensibility.

3.2.1.  Entry Names

   Entry names MUST be specified in a standards track or IESG approved
   experimental RFC, or fall under the vendor namespace.  See
   Section 6.1 for the registration template.

3.2.1.1.  Server Entries

   These entries are used when the mailbox name argument to the new
   SETMETADATA command is the empty string or with the new GETMETADATA
   command.

   /comment
      Defines a comment or note associated with the server.

   /motd
      Defines a "message of the day" for the server.  This entry is
      always read-only - clients cannot change it.

   /admin
      Indicates a method for contacting the server administrator.  The
      value MUST be a URI (e.g., a mailto: or tel: URL).  This entry is
      always read-only - clients cannot change it.

   /vendor/<vendor-token>
      Defines the top-level of entries associated with the server as
      created by a particular product of some vendor.  This entry can be
      used by vendors to provide server or client specific annotations.
      The vendor-token MUST be registered with IANA, using the ACAP
      [RFC2244] vendor subtree registry.

3.2.1.2.  Mailbox Entries

   These entries are used when the mailbox name argument to the new
   SETMETADATA command is not the empty string, or with the new LIST-



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   EXTENDED selection option type, or in responses to these commands.

   /comment
      Defines a comment or note associated with a mailbox.

   /sort
      Defines the default sort criteria [I-D.ietf-imapext-sort] to use
      when first displaying the mailbox contents to the user, or NIL if
      sorting is not required.  Note that the presence of this attribute
      does not imply that the server supports the IMAP SORT
      [I-D.ietf-imapext-sort] extension - servers can choose to support
      or not support SORT independently of this extension.  In the
      absence of the SORT extension, clients can choose to interpret
      this entry as suggesting a client-side sort ordering of the
      corresponding mailbox.

   /thread
      Defines the default thread criteria [I-D.ietf-imapext-sort] to use
      when first displaying the mailbox contents to the user, or NIL if
      threading is not required.  If both sort and thread are not NIL,
      then threading should take precedence over sorting.  Note that the
      presence of this attribute does not imply that the server supports
      the IMAP THREAD [I-D.ietf-imapext-sort] extension - servers can
      choose to support or not support THREAD independently of this
      extension.  In the absence of the THREAD extension, clients can
      choose to interpret this entry as a client-side thread ordering of
      the corresponding mailbox.

   /check
      Boolean value "true" or "false" that indicates whether this
      mailbox should be checked at regular intervals by the client.  The
      interval in minutes is specified by the /checkperiod entry.

   /checkperiod
      Numeric value indicating a period of minutes that the client uses
      to determine the interval of regular 'new mail' checks for the
      corresponding mailbox.

   /vendor/<vendor-token>
      Defines the top-level of entries associated with a specific
      mailbox as created by a particular product of some vendor.  This
      entry can be used by vendors to provide client specific
      annotations.  The vendor-token MUST be registered with IANA, using
      the ACAP [RFC2244] vendor subtree registry.







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3.2.2.  Attribute Names

   Attribute names MUST be specified in a standards track or IESG
   approved experimental RFC.  See Section 6.1 for the registration
   template.

   All attribute names implicitly have a ".priv" and a ".shared" suffix
   which maps to private and shared versions of the entry.  Retrieving
   an annotation without using either suffix includes both.  The client
   MUST specify either a ".priv" or ".shared" suffix when setting an
   annotation.

   value
      A string or binary data representing the value of the annotation.
      To delete an annotation, the client can store "NIL" into the
      value.  The content represented by the string is determined by the
      Content-Type used to register the entry (see Section 6.1 for entry
      registration templates).  Where applicable, the registered
      Content-Type MUST include a charset parameter.  Text values SHOULD
      use the utf-8 [RFC3629] character set.
      Note that binary data (data which may contain the NUL octet) is
      allowed (e.g., for storing images etc), and this extension uses
      the "literal8" syntax element [RFC4466] to allow such data to be
      written to or read from the server.

   size
      The size of the value, in octets.  Set automatically by the
      server, read-only to clients.  If the client requests the size
      attribute for a non-existent entry, then the server MUST return
      "0" (zero) for the size.

3.3.  Private versus Shared and Access Control

   As discussed in the ANNOTATE [I-D.ietf-imapext-annotate] extension
   there is a need to support both private and shared annotations.  This
   document adopts the scheme used in [I-D.ietf-imapext-annotate] that
   adds two standard suffixes for all attributes: ".shared" and ".priv".
   A GETMETADATA or extended LIST command which specifies neither uses
   both.  SETMETADATA commands MUST explicitly use .priv or .shared
   suffixes.

   A user can only set and retrieve private or shared annotations on a
   mailbox which exists and is returned to them via a LIST or LSUB
   command, irrespective of whether they have read or write access to
   the actual message content of the mailbox.  If the client attempts to
   set or retrieve annotations on other mailboxes, the server MUST
   respond with a NO response.




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   If the METADATA extension is present, support for shared annotations
   is REQUIRED, whilst support for private annotations is OPTIONAL.
   This recognizes the fact that support for private annotations may
   introduce significantly more complexity to a server in terms of
   tracking ownership of the annotations, how quota is determined for
   users based on their own annotations etc.  Clients that support the
   METADATA extension MUST handle both shared and private annotations.


4.  IMAP Protocol Changes

4.1.  General Considerations

   The new SETMETADATA command and the METADATA response each have a
   mailbox name argument, indicating that the annotations being referred
   to are attached to the specified mailbox.  An empty string can be
   used for the mailbox name to signify server annotations.

   Both "*" and "%" list wildcard characters MAY be used in the mailbox
   name argument in the SETMETADATA command to match all possible
   occurrences of a mailbox name pattern.  However, "*" or "%" by
   themselves MUST NOT match the empty string (server) entries.  Server
   entries can only be accessed by explicitly using the empty string as
   the mailbox name.

   Servers SHOULD ensure that mailbox annotations are automatically
   moved when the mailbox they refer to is renamed, i.e. the annotations
   follow the mailbox.  Servers SHOULD delete annotations for a mailbox
   when the mailbox is deleted, so that a mailbox created with the same
   name as a previously existing mailbox does not inherit the old
   mailbox annotations.  Servers SHOULD allow annotations on all 'types'
   of mailbox, including ones reporting \Noselect for their LIST
   response.  Servers can implicitly remove \Noselect mailboxes when all
   child mailboxes are removed, and as such any annotations associated
   with the \Noselect mailbox SHOULD be removed.

   The server is allowed to impose limitations on the size of any one
   annotation or the total number of annotations for a single mailbox or
   for the server as a whole.  However, the server MUST accept a minimum
   annotation data size of at least 1024 bytes, and a minimum annotation
   count per server or mailbox of at least 10.

   Some annotations may be "read-only" - i.e. they are set by the server
   and cannot be changed by the client.  Also, such annotations may be
   "computed" - i.e. the value changes based on underlying properties of
   the mailbox.  For example, an annotation reporting the total size of
   all messages in the mailbox would change as messages are added or
   removed.  Or, an annotation containing an IMAP URL for the mailbox



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   would change if the mailbox was renamed.

4.2.  GETMETADATA Command

   This extension adds the GETMETADATA command.  This allows clients to
   retrieve server annotations.  Mailbox annotations are retrieved via
   the extended LIST command described in the next section.

   This command is only available in authenticated or selected state
   [RFC3501].

       Arguments:  entry-specifier
                   attribute-specifier

       Responses:  required METADATA response

       Result:     OK - command completed
                   NO - command failure: can't access annotations on
                        the server
                   BAD - command unknown or arguments invalid

   Example:

           C: a GETMETADATA /comment value.priv
           S: * METADATA /comment (value.priv "My comment")
           S: a OK GETMETADATA complete

      In the above example, the contents of the "value.priv" attribute
      for the "/comment" server entry is requested by the client and
      returned by the server.

   "*" and "%" wildcard characters can be used in the entry specifier to
   match one or more characters at that position, with the exception
   that "%" does not match the "/" hierarchy delimiter.  Thus an entry
   specifier of "/%" would match entries such as "/comment" and "/motd",
   but not "/comment/note".

   Example:

           C: a GETMETADATA /* value.priv
           S: * METADATA /comment (value.priv "My comment")
                         /motd (value.priv "Closed at 1 pm")
           S: a OK GETMETADATA complete

      In the above example, the contents of the "value.priv" attributes
      for any server entries are requested by the client and returned by
      the server.




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   Example:

           C: a GETMETADATA /% value
           S: * METADATA /comment (value.priv "My comment")
                                  (value.shared "Your comment")
                         /motd (value.priv "Its sunny outside!"
                               (value.shared "Today is a Holiday")
           S: a OK GETMETADATA complete

      In the above example, the contents of the "value" attributes for
      server entries at the top level of the entry hierarchy only, are
      requested by the client and returned by the server.  Both the
      .priv and .shared values are returned, as neither were explicitly
      requested.

   Entry and attribute specifiers can be lists of atomic specifiers, so
   that multiple items of each type may be returned in a single
   GETMETADATA command.

   Example:

           C: a GETMETADATA (/comment /motd) value.priv
           S: * METADATA /comment (value.priv "My comment")
                         /motd (value.priv "Its sunny outside!")
           S: a OK GETMETADATA complete

      In the above example, the contents of the "value.priv" attributes
      for the two server entries "/comment" and "/motd" are requested by
      the client and returned by the server.

   Example:

           C: a GETMETADATA /comment (value.priv
                                      size.priv)
           S: * METADATA /comment (value.priv "My comment"
                                   size.priv "10")
           S: a OK GETMETADATA complete

      In the above example, the contents of the "value.priv" and
      "size.priv" attributes for the "/comment" server entry are
      requested by the client and returned by the server.

4.3.  Extended LIST Command Extensions

   This extension adds the METADATA LIST command selection and return
   option types, extending the LIST-EXTENDED extension.  This allows
   clients to retrieve mailbox annotations.




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   The LIST-EXTENDED "METADATA" selection option type is used to request
   that the extended LIST command match mailboxes which have an
   annotation with a specific entry and value.  It can also be used to
   test for the existence of a particular annotation entry on a mailbox.
   This selection option takes one or more entry/attribute/value triples
   to use as tests.  A mailbox matches this criteria if it has an entry,
   attribute and value matching the ones specified.  In the case of
   multiple criteria being specified, mailbox MUST only match when all
   criteria match ("and" operation).  To test for the existence of an
   entry, a test for the attribute "value" with the empty string "" as
   the value argument can be used.  To test for the absence of an entry,
   a test for the attribute "value" with NIL as the value argument can
   be used.  Clients SHOULD only use entries defined with a "text"
   Content-Type in the selection option arguments.

   Each entry/attribute/value triple specified in the selection option
   MAY include a match type specifier and MAY include a collation
   [I-D.ietf-imapext-i18n] identifier.  If the match type is specified,
   then that match operation MUST be used when matching the provided
   value with the corresponding annotation entry values in mailboxes.
   If the match type is not specified, then a default of "CONTAINS"
   (substring match) MUST be used.  If the collation identifier is
   specified, then that collation MUST be used to do the comparison of
   the annotation entry values being tested.  If the collation
   identifier is not specified, then the active collation as defined by
   [I-D.ietf-imapext-i18n] is used.  Possible values for the match type
   are:

       +----------+-----------------------------------------------+
       | Match    | Description                                   |
       +----------+-----------------------------------------------+
       | IS       | Equality test is done                         |
       | CONTAINS | Substring match is done                       |
       | GT       | Greater than relational test is done          |
       | GE       | Greater than or equal relational test is done |
       | LE       | Less than or equal relational test is done    |
       | LT       | Less than relational test is done             |
       +----------+-----------------------------------------------+

   The "NOT" match type modifier results in a negation of the comparison
   - i.e. it adds the ability to search for annotations that do not
   match or contain specific text.

   The LIST-EXTENDED "METADATA" return option type is used to request
   that the extended LIST command return specific annotation entries for
   each mailbox returned in the LIST responses.  A list of entries and
   attributes to return can be specified in a manner similar to the
   GETMETADATA command.



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   Example:

           C: a LIST "" "INBOX" RETURN (METADATA (/comment value.priv))
           S: * LIST "/" "INBOX"
                   (METADATA (/comment (value.priv "My comment")))
           S: a OK LIST complete

      In the above example, the contents of the "value.priv" attribute
      for the "/comment" entry for the mailbox INBOX is requested by the
      client and returned by the server.

   "*" and "%" wildcard characters can be used in the entry specifier to
   match one or more characters at that position, with the exception
   that "%" does not match the "/" hierarchy delimiter.  Thus an entry
   specifier of "/%" would match entries such as "/comment" and
   "/check", but not "/comment/note".

   Example:

           C: a LIST "" "INBOX" RETURN (METADATA (/* value.priv))
           S: * LIST "/" "INBOX"
                   (METADATA (/comment (value.priv "My comment")
                              /check (value.priv "true")))
           S: a OK LIST complete

      In the above example, the contents of the "value.priv" attributes
      for any entries for the mailbox INBOX are requested by the client
      and returned by the server.

   Example:

          C: a LIST "" "INBOX" RETURN (METADATA (/% value))
          S: * LIST "/" "INBOX"
                  (METADATA (/comment (value.priv "My comment")
                                      (value.shared "Your comment")
                             /motd (value.priv "Its sunny outside!"
                                   (value.shared "Today is a Holiday")))
          S: a OK LIST complete

      In the above example, the contents of the "value" attributes for
      entries for the mailbox INBOX at the top level of the entry
      hierarchy only, are requested by the client and returned by the
      server.  Both the .priv and .shared values are returned, as
      neither were explicitly requested.

   Entry and attribute specifiers can be lists of atomic specifiers, so
   that multiple items of each type may be returned in a single LIST
   command.



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   Example:

           C: a LIST "" "INBOX" RETURN (METADATA ((/comment /motd)
                                                  value.priv))
           S: * LIST "/" "INBOX"
                   (METADATA (/comment (value.priv "My comment")
                              /motd (value.priv "Its sunny outside!")))
           S: a OK LIST complete

      In the above example, the contents of the "value.priv" attributes
      for the two entries "/comment" and "/motd" for the mailbox INBOX
      are requested by the client and returned by the server.

   Example:

         C: a LIST "" "INBOX" RETURN (METADATA (/comment
                                                (value.priv size.priv)))
         S: * LIST "/" "INBOX"
                 (METADATA (/comment (value.priv "My comment"
                                      size.priv "10")))
         S: a OK LIST complete

      In the above example, the contents of the "value.priv" and
      "size.priv" attributes for the "/comment" entry for the mailbox
      INBOX are requested by the client and returned by the server.

   Example:

           C: a LIST "" ("INBOX" "FOOBOX" "BARBOX") RETURN
                   (METADATA (/comment value.priv))
           S: * LIST "/" "INBOX"
                   (METADATA (/comment (value.priv "My comment")))
           S: * LIST "/" "FOOBOX"
                   (METADATA (/comment (value.priv "Another comment")))
           S: * LIST "/" "BARBOX"
                   (METADATA (/comment (value.priv NIL)))
           S: a OK LIST complete

      In the above example, the contents of the "value.priv" attribute
      for the "/comment" entry for the mailboxes INBOX, FOOBOX and
      BARBOX are requested by the client and returned by the server.
      Note that the mailbox BARBOX does not contain the entry, hence NIL
      is returned for the attribute value.

   Example:






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           C: a LIST (METADATA ("/comment" "value" "comm"
                                (NOT CONTAINS))) "" "*"
           S: * LIST () "/" "INBOX"
           S: * LIST (\NoInferiors) "/" "FOOBOX"
           S: a OK LIST complete

      In the above example, the client requests that any mailbox in the
      entire hierarchy that does not contain the text "comm" in any
      "value" attribute of the "/comment" entry be returned.  Two
      mailboxes are returned in separate responses.  Note that the
      client did not ask for annotations to be returned in the
      responses.

   Example:

           C: a LIST (METADATA ("/comment" "value" ""))
                     "" "*"
           S: * LIST () "/" "INBOX"
           S: * LIST (\NoInferiors) "/" "FOOBOX"
           S: a OK LIST complete

      In the above example, the client requests that any mailbox in the
      entire hierarchy containing the "/comment" entry be returned.  Two
      mailboxes are returned in separate responses.  Note that the
      client did not ask for annotations to be returned in the
      responses.

   Example:

           C: a LIST (METADATA ("/comment" "value" NIL))
                     "" "*"
           S: * LIST (\NoInferiors) "/" "BARBOX"
           S: a OK LIST complete

      In the above example, the client requests that any mailbox in the
      entire hierarchy that does not have a "/comment" entry be
      returned.  One mailbox is returned in a response.  Note that the
      client did not ask for annotations to be returned in the
      responses.

   Example:










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           C: a LIST (METADATA ("/comment" "value" "HELP"
                                (IS "i;octet")) "" "*"
                     RETURN (METADATA (/comment size.priv))
           S: * LIST "/" "INBOX"
                   (METADATA (/comment (size.priv "10")))
           S: * LIST "/" "FOOBOX"
                   (METADATA (/comment (size.priv "15")))
           S: a OK LIST complete

      In the above example, the client requests that any mailbox in the
      entire hierarchy with the exact text "HELP" in any "value"
      attribute of the "/comment" entry be returned.  The client
      provides an explicit match type and collation identifier.  Two
      mailboxes are returned in separate responses.  The client also
      asked for annotation sizes to be returned in the responses.

4.3.1.  Unsolicited LIST response

   Servers SHOULD send unsolicited LIST responses if mailbox annotations
   are changed by a third-party, allowing servers to keep clients
   updated with changes.  Unless explicitly changed by an IMAP
   extension, unsolicited mailbox annotations MUST only be returned for
   the currently selected mailbox.

   Unsolicited LIST responses MUST only contain entry names, not the
   attributes and values.  If the client wants to update any cached
   values it must explicitly retrieve those using a LIST command.

   The LIST response can contain multiple entries in a single response,
   but the server is free to return multiple responses for each entry or
   group of entries if it desires.

   Example:

           C: a NOOP
           S: * LIST "/" "INBOX" (METADATA (/comment))
           S: a OK NOOP complete

      In the above example, the server sends an unsolicited LIST
      response indicating that the "/comment" entry of the mailbox
      "INBOX" has been changed.

4.4.  SETMETADATA Command

   This extension adds the SETMETADATA command.  This allows clients to
   set annotations.

   This command is only available in authenticated or selected state



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   [RFC3501].

       Arguments:  mailbox-name
                   entry
                   attribute-value
                   list of entry, attribute-values

       Responses:  no specific responses for this command

       Result:     OK - command completed
                   NO - command failure: can't set annotations,
                        or annotation too big or too many
                   BAD - command unknown or arguments invalid

   This command sets the specified list of entries by adding or
   replacing the specified attributes with the values provided, on the
   specified existing mailboxes.  Clients can use NIL for values of
   attributes it wants to remove from entries.  The server MAY return a
   METADATA response containing the updated annotation data.  Clients
   MUST NOT assume that a METADATA response will be sent, and MUST
   assume that if the command succeeds then the annotation has been
   changed.

   If the server is unable to set an annotation because the size of its
   value is too large, the server MUST return a tagged NO response with
   a "[METADATA TOOBIG]" response code.

   If the server is unable to set a new annotation because the maximum
   number of allowed annotations has already been reached, the server
   MUST return a tagged NO response with a "[METADATA TOOMANY]" response
   code.

   If the server is unable to set a new annotation because it does not
   support private annotations on one of the specified mailboxes, the
   server MUST return a tagged NO response with a "[METADATA NOPRIVATE]"
   response code.

   Example:

           C: a SETMETADATA INBOX /comment
                                    (value.priv "My new comment")
           S: a OK SETMETADATA complete

      In the above example, the entry "/comment" for the mailbox "INBOX"
      is created (if not already present) and the private attribute
      "value" with data set to "My new comment" is created if not
      already present, or replaced if it previously exists.




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   Example:

           C: a SETMETADATA INBOX /comment (value.priv NIL)
           S: a OK SETMETADATA complete

      In the above example, the private "value" attribute of the entry
      "/comment" is removed from the mailbox "INBOX".

   Annotations on multiple mailboxes can be set in a single SETMETADATA
   command by using a wildcard specification for the mailbox name.

   Example:

           C: a SETMETADATA INBOX.% /comment
                                      (value.priv "My new comment")
           S: a OK SETMETADATA complete

      In the above example, the entry "/comment" for all mailboxes at
      the top-level of the "INBOX" hierarchy are created (if not already
      present) and the private attribute "value" are created
      respectively for each entry if not already present, or replaced if
      they previously existed.

   Multiple entries can be set in a single SETMETADATA command by
   listing entry-attribute-value pairs in the list.

   Example:

           C: a SETMETADATA INBOX (/comment
                                     (value.priv "My new comment")
                                     /thread
                                     (value.priv "REFERENCES ALL"))
           S: a OK SETMETADATA complete

      In the above example, the entries "/comment" and "/thread" for the
      mailbox "INBOX" are created (if not already present) and the
      "value.priv" attributes are created respectively for each entry if
      not already present, or replaced if they previously existed.

   Multiple attributes can be set in a single SETMETADATA command by
   listing multiple attribute-value pairs in the entry list.

   Example:

           C: a SETMETADATA INBOX /comment
                                (value.priv "My new comment"
                                 value.shared "foo's bar")
           S: a OK SETMETADATA complete



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      In the above example, the entry "/comment" for the mailbox "INBOX"
      is created (if not already present) and the attributes
      "value.priv" and "value.shared" are created if not already
      present, or replaced if they previously existed.

   Example:

           C: a SETMETADATA INBOX /comment
                                    (value.priv "My new comment")
           S: a NO [METADATA TOOMANY] SETMETADATA failed

      In the above example, the server is unable to set the requested
      (new) annotation as it has reached the limit on the number of
      annotations it can support on the specified mailbox.

4.5.  METADATA Response

   The METADATA response displays results of a GETMETADATA command, or
   can be returned as an unsolicited response at anytime by the server
   in response to a change in a server annotation.

   Servers SHOULD send unsolicited METADATA responses if server
   annotations are changed by a third-party, allowing servers to keep
   clients updated with changes.

   Unsolicited METADATA responses MUST only contain entry names, not the
   attributes and values.  If the client wants to update any cached
   values it must explicitly retrieve those using a GETMETADATA command.

   The METADATA response can contain multiple entries in a single
   response, but the server is free to return multiple responses for
   each entry or group of entries if it desires.

   This response is only available in authenticated or selected state
   [RFC3501].

4.5.1.  METADATA response with attributes and values

   The response consists of a list of entries each of which has a list
   of attribute-value pairs.

   Example:

           C: a GETMETADATA /comment value.priv
           S: * METADATA /comment (value.priv "My comment")
           S: a OK GETMETADATA complete





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      In the above example, a single entry with a single attribute-value
      pair is returned by the server.

   Example:

           C: a GETMETADATA (/comment /motd) value.priv
           S: * METADATA /comment (value.priv "My comment")
                         /motd (value.priv "Its sunny outside!")
           S: a OK GETMETADATA complete

      In the above example, two entries each with a single attribute-
      value pair is returned by the server.

   Example:

           C: a GETMETADATA (/comment /motd) value.priv
           S: * METADATA /comment (value.priv "My comment")
           S: * METADATA /motd (value.priv "Its sunny outside!")
           S: a OK GETMETADATA complete

      In the above example, the server returns two separate responses
      for each of the two entries requested.

   Example:

           C: a GETMETADATA /comment (value.priv size.priv)
           S: * METADATA /comment (value.priv "My comment"
                                          size.priv "10")
           S: a OK GETMETADATA complete

      In the above example, a single entry with two attribute-value
      pairs is returned by the server.

4.5.2.  Unsolicited METADATA response without attributes and values

   The response consists of a parenthesized list of entries, each of
   which have changed on the server.

   Example:

           C: a NOOP
           S: * METADATA (/comment)
           S: a OK NOOP complete

      In the above example, the server indicates that the "/comment"
      server entry has been changed.

   Example:



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           C: a NOOP
           S: * METADATA (/comment /motd)
           S: a OK NOOP complete

      In the above example, the server indicates a change to two server
      entries.


5.  Formal Syntax

   The following syntax specification uses the Augmented Backus-Naur
   Form (ABNF) notation as specified in [RFC4234].

   Non-terminals referenced but not defined below are as defined by
   [RFC3501] with the new definitions in [RFC4466] superseding those in
   [RFC3501].

   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.

    annotate-data     = "METADATA" SP entry-list

    att-select        = "value" / "value.priv" / "value.shared"
                       ; the only attributes that can be selected

    att-value         = attrib SP value

    attrib            = astring
                        ; dot-separated attribute name
                        ; MUST NOT contain "*" or "%"

    attribs           = attrib / "(" attrib *(SP attrib) ")"
                        ; one or more attribute specifiers

    capability        =/ "METADATA"
                        ; defines the capability for this extension

    command-auth      =/ setmetadata / getmetadata
                        ; adds to original IMAP command

    collation         = astring
                        ; collation identifier as defined by
                        ; [I-D.newman-i18n-comparator]

    entries           = entry-match /
                        "(" entry-match *(SP entry-match) ")"



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                        ; entry specifiers that can include wildcards

    entry             = astring
                        ; slash-separated path to entry
                        ; MUST NOT contain "*" or "%"

    entry-att         = entry SP "(" att-value *(SP att-value) ")"

    entry-list        = entry-att *(SP entry-att) /
                        "(" entry *(SP entry) ")"
                        ; entry attribute-value pairs list for
                        ; GETMETADATA response, or
                        ; parenthesised entry list for unsolicited
                        ; notification of annotation changes

    entry-match       = list-mailbox
                        ; slash-separated path to entry
                        ; MAY contain "*" or "%" for use as wildcards

    getmetadata       = "GETMETADATA" SP entries SP attribs

    list-select-base-opt =/ "METADATA" SP
                            "(" list-select-metadata
                                 *(SP list-select-metadata) ")"
                        ; adds a new selection option type to
                        ; LIST-EXTENDED. When evaluating multiple entry,
                        ; attribute, value combinations, a match to
                        ; a mailbox must occur when all items match.


    list-select-metadata = entry-match SP att-select SP value
                           [SP "(" matchtype [SP collation] ")"]
                        ; value set to the empty string means match
                        ; if that entry and attribute exist.
                        ; value set to NIL means match if that entry
                        ; and attribute do not exist.
                        ; An optional match type and collation can also
                        ; be specified.

    matchtype         = ["NOT" SP] ("IS" / "CONTAINS" /
                                    "GT" / "GE" / "LE" / "LT")
                        ; match types for LIST-EXTENDED string
                        ; comparisons - see Section 4.3.

    response-payload  =/ annotate-data
                        ; adds to original IMAP data responses

    resp-text-code    =/ "METADATA" SP ("TOOBIG" / "TOOMANY" /



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                                        "NOPRIVATE")
                        ; new response codes for SETMETADATA
                        ; failures

    setmetadata       = "SETMETADATA" SP list-mailbox
                                      SP setentryatt
                        ; empty string for list-mailbox implies
                        ; server annotation.

    setentryatt       = entry-att / "(" entry-att *(SP entry-att) ")"

    value             = nstring / literal8


6.  IANA Considerations

   Entry names MUST be specified in a standards track or IESG approved
   experimental RFC, or fall under the vendor namespace.  Attribute
   names MUST be specified in a standards track or IESG approved
   experimental RFC.

   Each entry registration MUST include a content-type that is used to
   indicate the nature of the annotation value.  Where applicable a
   charset parameter MUST be included with the content-type.



























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6.1.  Entry and Attribute Registration Template

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [ ] Entry        [ ] Attribute

       [ ] Mailbox      [ ] Server

       Name: ______________________________

       Description: _______________________

       ____________________________________

       ____________________________________

       Content-type:   ____________________

       Contact person: ____________________

               email:  ____________________

6.2.  Server Entry Registrations

   The following templates specify the IANA registrations of annotation
   entries specified in this document.






















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6.2.1.  /comment

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [ ] Mailbox      [x] Server

       Name: /comment

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name

6.2.2.  /motd

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [ ] Mailbox      [x] Server

       Name: /motd

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name










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6.2.3.  /admin

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [ ] Mailbox      [x] Server

       Name: /admin

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name

6.3.  Mailbox Entry Registrations

   The following templates specify the IANA registrations of annotation
   entries specified in this document.

6.3.1.  /comment

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [x] Mailbox      [ ] Server

       Name: /comment

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name





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6.3.2.  /sort

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [x] Mailbox      [ ] Server

       Name: /sort

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name

6.3.3.  /thread

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [x] Mailbox      [ ] Server

       Name: /thread

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name










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6.3.4.  /check

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [x] Mailbox      [ ] Server

       Name: /check

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name

6.3.5.  /checkperiod

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [x] Entry        [ ] Attribute

       [x] Mailbox      [ ] Server

       Name: /checkperiod

       Description: Defined in IMAP METADATA extension document.

       Content-type:   text/plain; charset=utf-8

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name

6.4.  Attribute Registrations

   The following templates specify the IANA registrations of annotation
   attributes specified in this document.





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6.4.1.  value

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [ ] Entry        [x] Attribute

       [ ] Mailbox      [ ] Server

       Name: value

       Description: Defined in IMAP METADATA extension document.

       Content-type:   -

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name

6.4.2.  size

       To: iana@iana.org
       Subject: IMAP METADATA Registration

       Please register the following IMAP METADATA item:

       [ ] Entry        [x] Attribute

       [ ] Mailbox      [ ] Server

       Name: size

       Description: Defined in IMAP METADATA extension document.

       Content-type:   -

       Contact person: Cyrus Daboo

               email:  cyrus@daboo.name

6.5.  LIST-EXTENDED Registration

           To: iana@iana.org
           Subject: Registration of LIST-EXTENDED option METADATA

           LIST-EXTENDED option name: METADATA



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           LIST-EXTENDED option type: SELECTION

           Implied return options(s): (none)

           LIST-EXTENDED option description:
             The "METADATA" selection option type is used to request
             that the extended LIST command match mailboxes which have
             an annotation with a specific entry and value.  It can
             also be used to test for the existence of a particular
             annotation entry on a mailbox.

           Published specification : XXXX, Section 4.3.

           Security considerations: XXXX, Section 7.

           Intended usage: COMMON

           Person and email address to contact for further information:
              Cyrus Daboo <cyrus@daboo.name>

           Owner/Change controller: iesg@ietf.org



           To: iana@iana.org
           Subject: Registration of LIST-EXTENDED option METADATA

           LIST-EXTENDED option name: METADATA

           LIST-EXTENDED option type: RETURN

           LIST-EXTENDED option description: Causes the LIST command to
           return the specified mailbox annotations.

           Published specification : XXXX, Section 4.3.

           Security considerations: XXXX, Section 7.

           Intended usage: COMMON

           Person and email address to contact for further information:
              Cyrus Daboo <cyrus@daboo.name>

           Owner/Change controller: iesg@ietf.org







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7.  Security Considerations

   Annotations whose values are intended to remain private MUST use
   .priv values, and not .shared values which may be accessible to other
   users.

   Annotations can contain arbitrary sized data.  As such servers MUST
   ensure that size limits are enforced to prevent a user from using up
   all available space on a server and preventing use by others.

   Excluding the above issues the METADATA extension does not raise any
   security considerations that are not present in the base IMAP
   protocol, and these issues are discussed in [RFC3501].


8.  References

8.1.  Normative References

   [I-D.ietf-imapext-i18n]
              Newman, C., "Internet Message Access Protocol
              Internationalization", draft-ietf-imapext-i18n-06 (work in
              progress), March 2006.

   [I-D.ietf-imapext-list-extensions]
              Leiba, B. and A. Melnikov, "IMAP4 LIST Command
              Extensions", draft-ietf-imapext-list-extensions-17 (work
              in progress), April 2006.

   [I-D.ietf-imapext-sort]
              Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS
              PROTOCOL - SORT AND THREAD EXTENSION",
              draft-ietf-imapext-sort-17 (work in progress), May 2004.

   [I-D.newman-i18n-comparator]
              Newman, C., "Internet Application Protocol Collation
              Registry", draft-newman-i18n-comparator-13 (work in
              progress), August 2006.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2244]  Newman, C. and J. Myers, "ACAP -- Application
              Configuration Access Protocol", RFC 2244, November 1997.

   [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
              4rev1", RFC 3501, March 2003.




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   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC4234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [RFC4466]  Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
              ABNF", RFC 4466, April 2006.

8.2.  Informative References

   [I-D.ietf-imapext-annotate]
              Gellens, R. and C. Daboo, "IMAP ANNOTATE Extension",
              draft-ietf-imapext-annotate-15 (work in progress),
              March 2006.


Appendix A.  Acknowledgments

   The ideas expressed in this document are based on the message
   annotation document that was co-authored by Randall Gellens.  The
   participants of the IMAPext working group made significant
   contributions to this work.


Author's Address

   Cyrus Daboo
   Apple Inc.
   1 Infinite Loop
   Cupertino, CA  95014
   USA

   Email: cyrus@daboo.name
   URI:   http://www.apple.com/
















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