GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc5258

Network Working Group B. Leiba Request for Comments: 5258 IBM T.J. Watson Research Center Obsoletes: 3348 A. Melnikov Updates: 2193 Isode Limited Category: Standards Track June 2008

Internet Message Access Protocol version 4 - LIST Command Extensions

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.

Abstract

 IMAP4 has two commands for listing mailboxes: LIST and LSUB.  As we
 have added extensions, such as Mailbox Referrals, that have required
 specialized lists we have had to expand the number of list commands,
 since each extension must add its function to both LIST and LSUB, and
 these commands are not, as they are defined, extensible.  If we've
 needed the extensions to work together, we've had to add a set of
 commands to mix the different options, the set increasing in size
 with each new extension.  This document describes an extension to the
 base LIST command that will allow these additions to be done with
 mutually compatible options to the LIST command, avoiding the
 exponential increase in specialized list commands.

Leiba & Melnikov Standards Track [Page 1] RFC 5258 IMAP4 LIST Command Extensions June 2008

Table of Contents

 1.  Introduction and Overview  . . . . . . . . . . . . . . . . . .  3
 2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
 3.  Extended LIST Command  . . . . . . . . . . . . . . . . . . . .  4
   3.1.  Initial List of Selection Options  . . . . . . . . . . . .  7
   3.2.  Initial List of Return Options . . . . . . . . . . . . . .  8
   3.3.  General Principles for Returning LIST Responses  . . . . .  9
   3.4.  Additional Requirements on LIST-EXTENDED Clients . . . . .  9
   3.5.  CHILDINFO Extended Data Item . . . . . . . . . . . . . . . 10
 4.  The CHILDREN Return Option . . . . . . . . . . . . . . . . . . 11
 5.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
 6.  Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . . . 19
 7.  Internationalization Considerations  . . . . . . . . . . . . . 22
 8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 23
 9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 23
   9.1.  Guidelines for IANA  . . . . . . . . . . . . . . . . . . . 23
   9.2.  Registration Procedure and Change Control  . . . . . . . . 23
   9.3.  Registration Template for LIST-EXTENDED Options  . . . . . 25
   9.4.  Initial LIST-EXTENDED Option Registrations . . . . . . . . 25
   9.5.  Registration Template for LIST-EXTENDED Extended Data
         Item . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
   9.6.  Initial LIST-EXTENDED Extended Data Item Registrations . . 28
 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29
 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
   11.1. Normative References . . . . . . . . . . . . . . . . . . . 29
   11.2. Informative References . . . . . . . . . . . . . . . . . . 30

Leiba & Melnikov Standards Track [Page 2] RFC 5258 IMAP4 LIST Command Extensions June 2008

1. Introduction and Overview

 The LIST command is extended by amending the syntax to allow options
 and multiple patterns to be specified.  The list of options replaces
 the several commands that are currently used to mix and match the
 information requested.  The new syntax is backward compatible, with
 no ambiguity: the new syntax is being used if one of the following
 conditions is true:
 1.  if the first word after the command name begins with a
     parenthesis ("LIST selection options")
 2.  if the second word after the command name begins with a
     parenthesis ("multiple mailbox patterns")
 3.  if the LIST command has more than 2 parameters ("LIST return
     options")
 Otherwise the original syntax is used.
 By adding options to the LIST command, we are announcing the intent
 to phase out and eventually to deprecate the RLIST and RLSUB commands
 described in [MBRef].  We are also defining the mechanism to request
 extended mailbox information, such as is described in the Child
 Mailbox Extension [CMbox].  The base LSUB command is not deprecated
 by this extension; rather, this extension adds a way to obtain
 subscription information with more options, with those server
 implementations that support it.  Clients that simply need a list of
 subscribed mailboxes, as provided by the LSUB command, SHOULD
 continue to use that command.
 This document defines an IMAP4 extension that is identified by the
 capability string "LIST-EXTENDED".  The LIST-EXTENDED extension makes
 the following changes to the IMAP4 protocol, which are described in
 more detail in Section 3 and Section 4:
 a.  defines new syntax for LIST command options.
 b.  extends LIST to allow for multiple mailbox patterns.
 c.  adds LIST command selection options: SUBSCRIBED, REMOTE, and
     RECURSIVEMATCH.
 d.  adds LIST command return options: SUBSCRIBED and CHILDREN.
 e.  adds new mailbox attributes: "\NonExistent", "\Subscribed",
     "\Remote", "\HasChildren", and "\HasNoChildren".

Leiba & Melnikov Standards Track [Page 3] RFC 5258 IMAP4 LIST Command Extensions June 2008

 f.  adds CHILDINFO extended data item.

2. Conventions Used in This Document

 In examples, "C:" indicates lines sent by a client that is connected
 to a server.  "S:" indicates lines sent by the server to the client.
 The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
 are used in this document as specified in RFC 2119 [Kwds].
 The term "canonical LIST pattern" refers to the canonical pattern
 constructed internally by the server from the reference and mailbox
 name arguments (Section 6.3.8 of [IMAP4]).  The [IMAP4] LIST command
 returns only mailboxes that match the canonical LIST pattern.
 Other terms are introduced where they are referenced for the first
 time.

3. Extended LIST Command

 This extension updates the syntax of the LIST command to allow for
 multiple mailbox patterns to be specified, if they are enclosed in
 parentheses.  A mailbox name matches a list of mailbox patterns if it
 matches at least one mailbox pattern.  If a mailbox name matches
 multiple mailbox patterns from the list, the server SHOULD return
 only a single LIST response.
 Note that the non-extended LIST command is required to treat an empty
 ("" string) mailbox name argument as a special request to return the
 hierarchy delimiter and the root name of the name given in the
 reference parameter (as per [IMAP4]).  However, ANY extended LIST
 command (extended in any of 3 ways specified in Section 1, or any
 combination thereof) MUST NOT treat the empty mailbox name as such a
 special request, and any regular processing described in this
 document applies.  In particular, if an extended LIST command has
 multiple mailbox names and one (or more) of them is the empty string,
 the empty string MUST be ignored for the purpose of matching.
 Some servers might restrict which patterns are allowed in a LIST
 command.  If a server doesn't accept a particular pattern, it MUST
 silently ignore it.
 The LIST command syntax is also extended in two additional ways: by
 adding a parenthesized list of command options between the command
 name and the reference name (LIST selection options) and an optional

Leiba & Melnikov Standards Track [Page 4] RFC 5258 IMAP4 LIST Command Extensions June 2008

 list of options at the end that control what kind of information
 should be returned (LIST return options).  See the formal syntax in
 Section 6 for specific details.
 A LIST selection option tells the server which mailbox names should
 be selected by the LIST operation.  The server should return
 information about all mailbox names that match any of the "canonical
 LIST pattern" (as described above) and satisfy additional selection
 criteria (if any) specified by the LIST selection options.  Let's
 call any such mailbox name a "matched mailbox name".  When multiple
 selection options are specified, the server MUST return information
 about mailbox names that satisfy every selection option, unless a
 description of a particular specified option prescribes special
 rules.  An example of an option prescribing special rules is the
 RECURSIVEMATCH selection option described later in this section.  We
 will use the term "selection criteria" when referring collectively to
 all selection options specified in a LIST command.
 A LIST return option controls which information is returned for each
 matched mailbox name.  Note that return options MUST NOT cause the
 server to report information about additional mailbox names.  If the
 client has not specified any return option, only information about
 attributes should be returned by the server.  (Of course, the server
 is allowed to include any other information at will.)
 Both selection and return command options will be defined in this
 document and in approved extension documents; each option will be
 enabled by a capability string (one capability may enable multiple
 options), and a client MUST NOT send an option for which the server
 has not advertised support.  A server MUST respond to options it does
 not recognize with a BAD response.  The client SHOULD NOT specify any
 option more than once; however, if the client does this, the server
 MUST act as if it received the option only once.  The order in which
 options are specified by the client is not significant.
 In general, each selection option except RECURSIVEMATCH will have a
 corresponding return option.  The REMOTE selection option is an
 anomaly in this regard, and does not have a corresponding return
 option.  That is because it expands, rather than restricts, the set
 of mailboxes that are returned.  Future extensions to this
 specification should keep parallelism in mind and define a pair of
 corresponding options.
 This extension is identified by the capability string
 "LIST-EXTENDED", and support for it is a prerequisite for any future
 extensions that require specialized forms of the LIST command.  Such
 extensions MUST refer to this document and MUST add their function
 through command options as described herein.  Note that extensions

Leiba & Melnikov Standards Track [Page 5] RFC 5258 IMAP4 LIST Command Extensions June 2008

 that don't require support for an extended LIST command, but use
 extended LIST responses (see below), don't need to advertise the
 "LIST-EXTENDED" capability string.
 This extension also defines extensions to the LIST response, allowing
 a series of extended fields at the end, a parenthesized list of
 tagged data (also referred to as "extended data item").  The first
 element of an extended field is a tag, which identifies the type of
 data.  Tags MUST be registered with IANA, as described in Section 9.5
 of this document.  An example of such an extended set might be
 tablecloth (("edge" "lacy") ("color" "red"))) (X-Sample "text"))
 or
 tablecloth ("edge" "lacy")) (X-Sample "text" "more text"))
 See the formal syntax, in Section 6, for the full syntactic details.
 The server MUST NOT return any extended data item unless the client
 has expressed its ability to support extended LIST responses, for
 example, by using an extended LIST command.  The server MAY return
 data in the extended fields that was not directly solicited by the
 client in the corresponding LIST command.  For example, the client
 can enable extra extended fields by using another IMAP extension that
 make use of the extended LIST responses.  The client MUST ignore all
 extended fields it doesn't recognize.
 The LIST-EXTENDED capability also defines several new mailbox
 attributes.
 The "\NonExistent" attribute indicates that a mailbox name does not
 refer to an existing mailbox.  Note that this attribute is not
 meaningful by itself, as mailbox names that match the canonical LIST
 pattern but don't exist must not be returned unless one of the two
 conditions listed below is also satisfied:
 a.  The mailbox name also satisfies the selection criteria (for
     example, it is subscribed and the "SUBSCRIBED" selection option
     has been specified).
 b.  "RECURSIVEMATCH" has been specified, and the mailbox name has at
     least one descendant mailbox name that does not match the LIST
     pattern and does match the selection criteria.
 In practice, this means that the "\NonExistent" attribute is usually
 returned with one or more of "\Subscribed", "\Remote",
 "\HasChildren", or the CHILDINFO extended data item (see their
 description below).

Leiba & Melnikov Standards Track [Page 6] RFC 5258 IMAP4 LIST Command Extensions June 2008

 The "\NonExistent" attribute implies "\NoSelect".  The "\NonExistent"
 attribute MUST be supported and MUST be accurately computed.

3.1. Initial List of Selection Options

 The selection options defined in this specification are as follows:
 SUBSCRIBED -  causes the LIST command to list subscribed names,
    rather than the existing mailboxes.  This will often be a subset
    of the actual mailboxes.  It's also possible for this list to
    contain the names of mailboxes that don't exist.  In any case, the
    list MUST include exactly those mailbox names that match the
    canonical list pattern and are subscribed to.  This option is
    intended to supplement the LSUB command.  Of particular note are
    the mailbox attributes as returned by this option, compared with
    what is returned by LSUB.  With the latter, the attributes
    returned may not reflect the actual attribute status on the
    mailbox name, and the \NoSelect attribute has a second special
    meaning (it indicates that this mailbox is not, itself,
    subscribed, but that it has descendant mailboxes that are).  With
    the SUBSCRIBED selection option described here, the attributes are
    accurate and complete, and have no special meanings.  "LSUB" and
    "LIST (SUBSCRIBED)" are, thus, not the same thing, and some
    servers must do significant extra work to respond to "LIST
    (SUBSCRIBED)".  Because of this, clients SHOULD continue to use
    "LSUB" unless they specifically want the additional information
    offered by "LIST (SUBSCRIBED)".
    This option defines a new mailbox attribute, "\Subscribed", that
    indicates that a mailbox name is subscribed to.  The "\Subscribed"
    attribute MUST be supported and MUST be accurately computed when
    the SUBSCRIBED selection option is specified.
    Note that the SUBSCRIBED selection option implies the SUBSCRIBED
    return option (see below).
 REMOTE -  causes the LIST command to show remote mailboxes as well as
    local ones, as described in [MBRef].  This option is intended to
    replace the RLIST command and, in conjunction with the SUBSCRIBED
    selection option, the RLSUB command.
    This option defines a new mailbox attribute, "\Remote", that
    indicates that a mailbox is a remote mailbox.  The "\Remote"
    attribute MUST be accurately computed when the REMOTE option is
    specified.
    The REMOTE selection option has no interaction with other options.
    Its effect is to tell the server to apply the other options, if

Leiba & Melnikov Standards Track [Page 7] RFC 5258 IMAP4 LIST Command Extensions June 2008

    any, to remote mailboxes, in addition to local ones.  In
    particular, it has no interaction with RECURSIVEMATCH (see below).
    A request for (REMOTE RECURSIVEMATCH) is invalid, because a
    request for (RECURSIVEMATCH) is.  A request for (REMOTE
    RECURSIVEMATCH SUBSCRIBED) is asking for all subscribed mailboxes,
    both local and remote.
 RECURSIVEMATCH -  this option forces the server to return information
    about parent mailboxes that don't match other selection options,
    but have some submailboxes that do.  Information about children is
    returned in the CHILDINFO extended data item, as described in
    Section 3.5.
    Note 1: In order for a parent mailbox to be returned, it still has
    to match the canonical LIST pattern.
    Note 2: When returning the CHILDINFO extended data item, it
    doesn't matter whether or not the submailbox matches the canonical
    LIST pattern.  See also example 9 in Section 5.
    The RECURSIVEMATCH option MUST NOT occur as the only selection
    option (or only with REMOTE), as it only makes sense when other
    selection options are also used.  The server MUST return BAD
    tagged response in such case.
    Note that even if the RECURSIVEMATCH option is specified, the
    client MUST still be able to handle a case when a CHILDINFO
    extended data item is returned and there are no submailboxes that
    meet the selection criteria of the subsequent LIST command, as
    they can be deleted/renamed after the LIST response was sent, but
    before the client had a chance to access them.

3.2. Initial List of Return Options

 The return options defined in this specification are as follows:
 SUBSCRIBED -  causes the LIST command to return subscription state
    for all matching mailbox names.  The "\Subscribed" attribute MUST
    be supported and MUST be accurately computed when the SUBSCRIBED
    return option is specified.  Further, all mailbox flags MUST be
    accurately computed (this differs from the behavior of the LSUB
    command).
 CHILDREN -  requests mailbox child information as originally proposed
    in [CMbox].  See Section 4, below, for details.  This option MUST
    be supported by all servers.

Leiba & Melnikov Standards Track [Page 8] RFC 5258 IMAP4 LIST Command Extensions June 2008

3.3. General Principles for Returning LIST Responses

 This section outlines several principles that can be used by server
 implementations of this document to decide whether a LIST response
 should be returned, as well as how many responses and what kind of
 information they may contain.
 1.  At most one LIST response should be returned for each mailbox
     name that matches the canonical LIST pattern.  Server
     implementors must not assume that clients will be able to
     assemble mailbox attributes and other information returned in
     multiple LIST responses.
 2.  There are only two reasons for including a matching mailbox name
     in the responses to the LIST command (note that the server is
     allowed to return unsolicited responses at any time, and such
     responses are not governed by this rule):
     A.  The mailbox name also satisfies the selection criteria.
     B.  The mailbox name doesn't satisfy the selection criteria, but
         it has at least one descendant mailbox name that satisfies
         the selection criteria and that doesn't match the canonical
         LIST pattern.
         For more information on this case, see the CHILDINFO extended
         data item described in Section 3.5.  Note that the CHILDINFO
         extended data item can only be returned when the
         RECURSIVEMATCH selection option is specified.
 3.  Attributes returned in the same LIST response must be treated
     additively.  For example, the following response
        S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach"
     means that the "Fruit/Peach" mailbox doesn't exist, but it is
     subscribed.

3.4. Additional Requirements on LIST-EXTENDED Clients

 All clients that support this extension MUST treat an attribute with
 a stronger meaning as implying any attribute that can be inferred
 from it.  For example, the client must treat the presence of the
 \NoInferiors attribute as if the \HasNoChildren attribute was also
 sent by the server.

Leiba & Melnikov Standards Track [Page 9] RFC 5258 IMAP4 LIST Command Extensions June 2008

 The following table summarizes inference rules described in
 Section 3.
              +--------------------+-------------------+
              | returned attribute | implied attribute |
              +--------------------+-------------------+
              |    \NoInferiors    |   \HasNoChildren  |
              |    \NonExistent    |     \NoSelect     |
              +--------------------+-------------------+

3.5. CHILDINFO Extended Data Item

 The CHILDINFO extended data item MUST NOT be returned unless the
 client has specified the RECURSIVEMATCH selection option.
 The CHILDINFO extended data item in a LIST response describes the
 selection criteria that has caused it to be returned and indicates
 that the mailbox has at least one descendant mailbox that matches the
 selection criteria.
 The LSUB command indicates this condition by using the "\NoSelect"
 attribute, but the LIST (SUBSCRIBED) command MUST NOT do that, since
 "\NoSelect" retains its original meaning here.  Further, the
 CHILDINFO extended data item is more general, in that it can be used
 with any extended set of selection criteria.
 Note: Some servers allow for mailboxes to exist without requiring
 their parent to exist.  For example, a mailbox "Customers/ABC" can
 exist while the mailbox "Customers" does not.  As CHILDINFO extended
 data item is not allowed if the RECURSIVEMATCH selection option is
 not specified, such servers SHOULD use the "\NonExistent
 \HasChildren" attribute pair to signal to the client that there is a
 descendant mailbox that matches the selection criteria.  See example
 11 in Section 5.
 The returned selection criteria allow the client to distinguish a
 solicited response from an unsolicited one, as well as to distinguish
 among solicited responses caused by multiple pipelined LIST commands
 that specify different criteria.
 Servers SHOULD ONLY return a non-matching mailbox name along with
 CHILDINFO if at least one matching child is not also being returned.
 That is, servers SHOULD suppress redundant CHILDINFO responses.
 Examples 8 and 10 in Section 5 demonstrate the difference between
 present CHILDINFO extended data item and the "\HasChildren"
 attribute.

Leiba & Melnikov Standards Track [Page 10] RFC 5258 IMAP4 LIST Command Extensions June 2008

 The following table summarizes interaction between the "\NonExistent"
 attribute and CHILDINFO (the first column indicates whether the
 parent mailbox exists):
 +--------+--------------+--------------------+----------------------+
 | exists |   meets the  |  has a child that  |       returned       |
 |        |   selection  |      meets the     |     LIST-EXTENDED    |
 |        |   criteria   | selection criteria |    attributes and    |
 |        |              |                    |       CHILDINFO      |
 +--------+--------------+--------------------+----------------------+
 |   no   |      no      |         no         |   no LIST response   |
 |        |              |                    |       returned       |
 |   yes  |      no      |         no         |   no LIST response   |
 |        |              |                    |       returned       |
 |   no   |      yes     |         no         |     (\NonExistent    |
 |        |              |                    |        <attr>)       |
 |   yes  |      yes     |         no         |       (<attr>)       |
 |   no   |      no      |         yes        |   (\NonExistent) +   |
 |        |              |                    |       CHILDINFO      |
 |   yes  |      no      |         yes        |    () + CHILDINFO    |
 |   no   |      yes     |         yes        |     (\NonExistent    |
 |        |              |                    |  <attr>) + CHILDINFO |
 |   yes  |      yes     |         yes        | (<attr>) + CHILDINFO |
 +--------+--------------+--------------------+----------------------+
 where <attr> is one or more attributes that correspond to the
 selection criteria; for example, for the SUBSCRIBED option the <attr>
 is \Subscribed.

4. The CHILDREN Return Option

 The CHILDREN return option implements the Child Mailbox Extension,
 originally proposed by Mike Gahrns and Raymond Cheng, of Microsoft
 Corporation.  Most of the information in this section is taken
 directly from their original specification [CMbox].  The CHILDREN
 return option is simply an indication that the client wants this
 information; a server MAY provide it even if the option is not
 specified.
 Many IMAP4 [IMAP4] clients present to the user a hierarchical view of
 the mailboxes that a user has access to.  Rather than initially
 presenting to the user the entire mailbox hierarchy, it is often
 preferable to show to the user a collapsed outline list of the
 mailbox hierarchy (particularly if there is a large number of
 mailboxes).  The user can then expand the collapsed outline hierarchy
 as needed.  It is common to include within the collapsed hierarchy a
 visual clue (such as a ''+'') to indicate that there are child
 mailboxes under a particular mailbox.  When the visual clue is

Leiba & Melnikov Standards Track [Page 11] RFC 5258 IMAP4 LIST Command Extensions June 2008

 clicked, the hierarchy list is expanded to show the child mailboxes.
 The CHILDREN return option provides a mechanism for a client to
 efficiently determine whether a particular mailbox has children,
 without issuing a LIST "" * or a LIST "" % for each mailbox name.
 The CHILDREN return option defines two new attributes that MUST be
 returned within a LIST response: \HasChildren and \HasNoChildren.
 Although these attributes MAY be returned in response to any LIST
 command, the CHILDREN return option is provided to indicate that the
 client particularly wants this information.  If the CHILDREN return
 option is present, the server MUST return these attributes even if
 their computation is expensive.
 \HasChildren
 The presence of this attribute indicates that the mailbox has child
      mailboxes.  A server SHOULD NOT set this attribute if there are
      child mailboxes and the user does not have permission to access
      any of them.  In this case, \HasNoChildren SHOULD be used.  In
      many cases, however, a server may not be able to efficiently
      compute whether a user has access to any child mailbox.  Note
      that even though the \HasChildren attribute for a mailbox must
      be correct at the time of processing of the mailbox, a client
      must be prepared to deal with a situation when a mailbox is
      marked with the \HasChildren attribute, but no child mailbox
      appears in the response to the LIST command.  This might happen,
      for example, due to children mailboxes being deleted or made
      inaccessible to the user (using access control) by another
      client before the server is able to list them.
 \HasNoChildren
 The presence of this attribute indicates that the mailbox has NO
      child mailboxes that are accessible to the currently
      authenticated user.
 It is an error for the server to return both a \HasChildren and a
 \HasNoChildren attribute in the same LIST response.
 Note: the \HasNoChildren attribute should not be confused with the
 IMAP4 [IMAP4] defined attribute \NoInferiors, which indicates that no
 child mailboxes exist now and none can be created in the future.

Leiba & Melnikov Standards Track [Page 12] RFC 5258 IMAP4 LIST Command Extensions June 2008

5. Examples

 1:   The first example shows the complete local hierarchy that will
      be used for the other examples.
    C: A01 LIST "" "*"
    S: * LIST (\Marked \NoInferiors) "/" "inbox"
    S: * LIST () "/" "Fruit"
    S: * LIST () "/" "Fruit/Apple"
    S: * LIST () "/" "Fruit/Banana"
    S: * LIST () "/" "Tofu"
    S: * LIST () "/" "Vegetable"
    S: * LIST () "/" "Vegetable/Broccoli"
    S: * LIST () "/" "Vegetable/Corn"
    S: A01 OK done
 2:   In the next example, we will see the subscribed mailboxes.  This
      is similar to, but not equivalent with, <LSUB "" "*">.  Note
      that the mailbox called "Fruit/Peach" is subscribed to, but does
      not actually exist (perhaps it was deleted while still
      subscribed).  The "Fruit" mailbox is not subscribed to, but it
      has two subscribed children.  The "Vegetable" mailbox is
      subscribed and has two children; one of them is subscribed as
      well.
    C: A02 LIST (SUBSCRIBED) "" "*"
    S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox"
    S: * LIST (\Subscribed) "/" "Fruit/Banana"
    S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach"
    S: * LIST (\Subscribed) "/" "Vegetable"
    S: * LIST (\Subscribed) "/" "Vegetable/Broccoli"
    S: A02 OK done
 3:   The next example shows the use of the CHILDREN option.  The
      client, without having to list the second level of hierarchy,
      now knows which of the top-level mailboxes have submailboxes
      (children) and which do not.  Note that it's not necessary for
      the server to return the \HasNoChildren attribute for the inbox,
      because the \NoInferiors attribute already implies that, and has
      a stronger meaning.
    C: A03 LIST () "" "%" RETURN (CHILDREN)
    S: * LIST (\Marked \NoInferiors) "/" "inbox"
    S: * LIST (\HasChildren) "/" "Fruit"
    S: * LIST (\HasNoChildren) "/" "Tofu"
    S: * LIST (\HasChildren) "/" "Vegetable"
    S: A03 OK done

Leiba & Melnikov Standards Track [Page 13] RFC 5258 IMAP4 LIST Command Extensions June 2008

 4:   In this example, we see more mailboxes that reside on another
      server.  This is similar to the command <RLIST "" "%">.
    C: A04 LIST (REMOTE) "" "%" RETURN (CHILDREN)
    S: * LIST (\Marked \NoInferiors) "/" "inbox"
    S: * LIST (\HasChildren) "/" "Fruit"
    S: * LIST (\HasNoChildren) "/" "Tofu"
    S: * LIST (\HasChildren) "/" "Vegetable"
    S: * LIST (\Remote) "/" "Bread"
    S: * LIST (\HasChildren \Remote) "/" "Meat"
    S: A04 OK done
 5:   The following example also requests the server to include
      mailboxes that reside on another server.  The server returns
      information about all mailboxes that are subscribed.  This is
      similar to the command <RLSUB "" "*">.  We also see the use of
      two selection options.
    C: A05 LIST (REMOTE SUBSCRIBED) "" "*"
    S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox"
    S: * LIST (\Subscribed) "/" "Fruit/Banana"
    S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach"
    S: * LIST (\Subscribed) "/" "Vegetable"
    S: * LIST (\Subscribed) "/" "Vegetable/Broccoli"
    S: * LIST (\Remote \Subscribed) "/" "Bread"
    S: A05 OK done
 6:   The following example requests the server to include mailboxes
      that reside on another server.  The server is asked to return
      subscription information for all returned mailboxes.  This is
      different from the example above.
      Note that the output of this command is not a superset of the
      output in the previous example, as it doesn't include LIST
      response for the non-existent "Fruit/Peach".
    C: A06 LIST (REMOTE) "" "*" RETURN (SUBSCRIBED)
    S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox"
    S: * LIST () "/" "Fruit"
    S: * LIST () "/" "Fruit/Apple"
    S: * LIST (\Subscribed) "/" "Fruit/Banana"
    S: * LIST () "/" "Tofu"
    S: * LIST (\Subscribed) "/" "Vegetable"
    S: * LIST (\Subscribed) "/" "Vegetable/Broccoli"
    S: * LIST () "/" "Vegetable/Corn"
    S: * LIST (\Remote \Subscribed) "/" "Bread"
    S: * LIST (\Remote) "/" "Meat"
    S: A06 OK done

Leiba & Melnikov Standards Track [Page 14] RFC 5258 IMAP4 LIST Command Extensions June 2008

 7:   In the following example, the client has specified multiple
      mailbox patterns.  Note that this example does not use the
      mailbox hierarchy used in the previous examples.
    C: BBB LIST "" ("INBOX" "Drafts" "Sent/%")
    S: * LIST () "/" "INBOX"
    S: * LIST (\NoInferiors) "/" "Drafts"
    S: * LIST () "/" "Sent/March2004"
    S: * LIST (\Marked) "/" "Sent/December2003"
    S: * LIST () "/" "Sent/August2004"
    S: BBB OK done
 8:   The following example demonstrates the difference between the
      \HasChildren attribute and the CHILDINFO extended data item.
      Let's assume there is the following hierarchy:
    C: C01 LIST "" "*"
    S: * LIST (\Marked \NoInferiors) "/" "inbox"
    S: * LIST () "/" "Foo"
    S: * LIST () "/" "Foo/Bar"
    S: * LIST () "/" "Foo/Baz"
    S: * LIST () "/" "Moo"
    S: C01 OK done
 If the client asks RETURN (CHILDREN), it will get this:
    C: CA3 LIST "" "%" RETURN (CHILDREN)
    S: * LIST (\Marked \NoInferiors) "/" "inbox"
    S: * LIST (\HasChildren) "/" "Foo"
    S: * LIST (\HasNoChildren) "/" "Moo"
    S: CA3 OK done
 A) Let's also assume that the mailbox "Foo/Baz" is the only
 subscribed mailbox.  Then we get this result:
    C: C02 LIST (SUBSCRIBED) "" "*"
    S: * LIST (\Subscribed) "/" "Foo/Baz"
    S: C02 OK done
 Now, if the client issues <LIST (SUBSCRIBED) "" "%">, the server will
 return no mailboxes (as the mailboxes "Moo", "Foo", and "Inbox" are
 NOT subscribed).  However, if the client issues this:
    C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%"
    S: * LIST () "/" "Foo" ("CHILDINFO" ("SUBSCRIBED"))
    S: C04 OK done

Leiba & Melnikov Standards Track [Page 15] RFC 5258 IMAP4 LIST Command Extensions June 2008

 (i.e., the mailbox "Foo" is not subscribed, but it has a child that
 is.)
 A1) If the mailbox "Foo" had also been subscribed, the last command
 would return this:
    C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%"
    S: * LIST (\Subscribed) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED"))
    S: C04 OK done
 or even this:
    C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%"
    S: * LIST (\Subscribed \HasChildren) "/" "Foo" ("CHILDINFO"
       ("SUBSCRIBED"))
    S: C04 OK done
 A2) If we assume instead that the mailbox "Foo" is not part of the
 original hierarchy and is not subscribed, the last command will give
 this result:
    C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%"
    S: * LIST (\NonExistent) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED"))
    S: C04 OK done
 B) Now, let's assume that no mailbox is subscribed.  In this case,
 the command <LIST (SUBSCRIBED RECURSIVEMATCH) "" "%"> will return no
 responses, as there are no subscribed children (even though "Foo" has
 children).
 C) And finally, suppose that only the mailboxes "Foo" and "Moo" are
 subscribed.  In that case, we see this result:
    C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" RETURN (CHILDREN)
    S: * LIST (\HasChildren \Subscribed) "/" "Foo"
    S: * LIST (\HasNoChildren \Subscribed) "/" "Moo"
    S: C04 OK done
 (which means that the mailbox "Foo" has children, but none of them is
 subscribed).
 9:   The following example demonstrates that the CHILDINFO extended
      data item is returned whether or not children mailboxes match
      the canonical LIST pattern.

Leiba & Melnikov Standards Track [Page 16] RFC 5258 IMAP4 LIST Command Extensions June 2008

      Let's assume there is the following hierarchy:
    C: D01 LIST "" "*"
    S: * LIST (\Marked \NoInferiors) "/" "inbox"
    S: * LIST () "/" "foo2"
    S: * LIST () "/" "foo2/bar1"
    S: * LIST () "/" "foo2/bar2"
    S: * LIST () "/" "baz2"
    S: * LIST () "/" "baz2/bar2"
    S: * LIST () "/" "baz2/bar22"
    S: * LIST () "/" "baz2/bar222"
    S: * LIST () "/" "eps2"
    S: * LIST () "/" "eps2/mamba"
    S: * LIST () "/" "qux2/bar2"
    S: D01 OK done
 And that the following mailboxes are subscribed:
    C: D02 LIST (SUBSCRIBED) "" "*"
    S: * LIST (\Subscribed) "/" "foo2/bar1"
    S: * LIST (\Subscribed) "/" "foo2/bar2"
    S: * LIST (\Subscribed) "/" "baz2/bar2"
    S: * LIST (\Subscribed) "/" "baz2/bar22"
    S: * LIST (\Subscribed) "/" "baz2/bar222"
    S: * LIST (\Subscribed) "/" "eps2"
    S: * LIST (\Subscribed) "/" "eps2/mamba"
    S: * LIST (\Subscribed) "/" "qux2/bar2"
    S: D02 OK done
 The client issues the following command first:
    C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*2"
    S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED"))
    S: * LIST (\Subscribed) "/" "foo2/bar2"
    S: * LIST (\Subscribed) "/" "baz2/bar2"
    S: * LIST (\Subscribed) "/" "baz2/bar22"
    S: * LIST (\Subscribed) "/" "baz2/bar222"
    S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED"))
    S: * LIST (\Subscribed) "/" "qux2/bar2"
    S: D03 OK done
 and the server may also include (but this would violate a SHOULD NOT
 in Section 3.5, because CHILDINFO is redundant)
    S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED"))
    S: * LIST (\NonExistent) "/" "qux2" ("CHILDINFO" ("SUBSCRIBED"))

Leiba & Melnikov Standards Track [Page 17] RFC 5258 IMAP4 LIST Command Extensions June 2008

 The CHILDINFO extended data item is returned for mailboxes "foo2",
 "baz2", and "eps2", because all of them have subscribed children,
 even though for the mailbox "foo2" only one of the two subscribed
 children matches the pattern, for the mailbox "baz2" all the
 subscribed children match the pattern, and for the mailbox "eps2"
 none of the subscribed children matches the pattern.
 Note that if the client issues
    C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*"
    S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED"))
    S: * LIST (\Subscribed) "/" "foo2/bar1"
    S: * LIST (\Subscribed) "/" "foo2/bar2"
    S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED"))
    S: * LIST (\Subscribed) "/" "baz2/bar2"
    S: * LIST (\Subscribed) "/" "baz2/bar22"
    S: * LIST (\Subscribed) "/" "baz2/bar222"
    S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED"))
    S: * LIST (\Subscribed) "/" "eps2/mamba"
    S: * LIST (\Subscribed) "/" "qux2/bar2"
    S: D03 OK done
 The LIST responses for mailboxes "foo2", "baz2", and "eps2" still
 have the CHILDINFO extended data item, even though this information
 is redundant and the client can determine it by itself.
 10:  The following example shows usage of multiple mailbox patterns.
      It also demonstrates that the presence of the CHILDINFO extended
      data item doesn't necessarily imply \HasChildren.
    C: a1 LIST "" ("foo" "foo/*")
    S: * LIST () "/" foo
    S: a1 OK done
    C: a2 LIST (SUBSCRIBED) "" "foo/*"
    S: * LIST (\Subscribed \NonExistent) "/" foo/bar
    S: a2 OK done
    C: a3 LIST (SUBSCRIBED RECURSIVEMATCH) "" foo RETURN (CHILDREN)
    S: * LIST (\HasNoChildren) "/" foo ("CHILDINFO" ("SUBSCRIBED"))
    S: a3 OK done
 11:  The following example shows how a server that supports missing
      mailbox hierarchy elements can signal to a client that didn't
      specify the RECURSIVEMATCH selection option that there is a
      child mailbox that matches the selection criteria.

Leiba & Melnikov Standards Track [Page 18] RFC 5258 IMAP4 LIST Command Extensions June 2008

    C: a1 LIST (REMOTE) "" *
    S: * LIST () "/" music/rock
    S: * LIST (\Remote) "/" also/jazz
    S: a1 OK done
    C: a2 LIST () "" %
    S: * LIST (\NonExistent \HasChildren) "/" music
    S: a2 OK done
    C: a3 LIST (REMOTE) "" %
    S: * LIST (\NonExistent \HasChildren) "/" music
    S: * LIST (\NonExistent \HasChildren) "/" also
    S: a3 OK done
    C: a3.1 LIST "" (% music/rock)
    S: * LIST () "/" music/rock
    S: a3.1 OK done
 Because "music/rock" is the only mailbox under "music", there's no
 need for the server to also return "music".  However clients must
 handle both cases.

6. Formal Syntax

 The following syntax specification uses the Augmented Backus-Naur
 Form (ABNF) as described in [ABNF].  Terms not defined here are taken
 from [IMAP4].  In particular, note that the version of "mailbox-list"
 below, which defines the payload of the LIST response, updates the
 version defined in the IMAP specification.  It is pointed to by
 "mailbox-data", which is defined in [IMAP4].
 "vendor-token" is defined in [ACAP].  Note that this normative
 reference to ACAP will be an issue in moving this spec forward, since
 it introduces a dependency on ACAP.  The definitions of
 "vendor-token" and of the IANA registry must eventually go somewhere
 else, in a document that can be moved forward on the standards track
 independently of ACAP.

Leiba & Melnikov Standards Track [Page 19] RFC 5258 IMAP4 LIST Command Extensions June 2008

 childinfo-extended-item =  "CHILDINFO" SP "("
             list-select-base-opt-quoted
             *(SP list-select-base-opt-quoted) ")"
             ; Extended data item (mbox-list-extended-item)
             ; returned when the RECURSIVEMATCH
             ; selection option is specified.
             ; Note 1: the CHILDINFO tag can be returned
             ; with and without surrounding quotes, as per
             ; mbox-list-extended-item-tag production.
             ; Note 2: The selection options are always returned
             ; quoted, unlike their specification in
             ; the extended LIST command.
 child-mbox-flag =  "\HasChildren" / "\HasNoChildren"
             ; attributes for CHILDREN return option, at most one
             ; possible per LIST response
 eitem-standard-tag =  atom
             ; a tag for extended list data defined in a Standard
             ; Track or Experimental RFC.
 eitem-vendor-tag =  vendor-token "-" atom
             ; a vendor-specific tag for extended list data
 list =      "LIST" [SP list-select-opts] SP mailbox SP mbox-or-pat
             [SP list-return-opts]
 list-return-opts =  "RETURN" SP
             "(" [return-option *(SP return-option)] ")"
             ; list return options, e.g., CHILDREN
 list-select-base-opt =  "SUBSCRIBED" / option-extension
             ; options that can be used by themselves
 list-select-base-opt-quoted =  DQUOTE list-select-base-opt DQUOTE
 list-select-independent-opt =  "REMOTE" / option-extension
             ; options that do not syntactically interact with
             ; other options
 list-select-mod-opt =  "RECURSIVEMATCH" / option-extension
             ; options that require a list-select-base-opt
             ; to also be present
 list-select-opt =  list-select-base-opt / list-select-independent-opt
             / list-select-mod-opt
             ; An option registration template is described in
             ; Section 9.3 of this document.

Leiba & Melnikov Standards Track [Page 20] RFC 5258 IMAP4 LIST Command Extensions June 2008

 list-select-opts =  "(" [
               (*(list-select-opt SP) list-select-base-opt
                *(SP list-select-opt))
             / (list-select-independent-opt
                *(SP list-select-independent-opt))
             ] ")"
             ; Any number of options may be in any order.
             ; If a list-select-mod-opt appears, then a
             ; list-select-base-opt must also appear.
             ; This allows these:
             ; ()
             ; (REMOTE)
             ; (SUBSCRIBED)
             ; (SUBSCRIBED REMOTE)
             ; (SUBSCRIBED RECURSIVEMATCH)
             ; (SUBSCRIBED REMOTE RECURSIVEMATCH)
             ; But does NOT allow these:
             ; (RECURSIVEMATCH)
             ; (REMOTE RECURSIVEMATCH)
 mailbox-list =  "(" [mbx-list-flags] ")" SP
             (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox
             [SP mbox-list-extended]
             ; This is the list information pointed to by the ABNF
             ; item "mailbox-data", which is defined in [IMAP4]
 mbox-list-extended =  "(" [mbox-list-extended-item
             *(SP mbox-list-extended-item)] ")"
 mbox-list-extended-item =  mbox-list-extended-item-tag SP
             tagged-ext-val
 mbox-list-extended-item-tag =  astring
             ; The content MUST conform to either "eitem-vendor-tag"
             ; or "eitem-standard-tag" ABNF productions.
             ; A tag registration template is described in this
             ; document in Section 9.5.
 mbx-list-oflag =/  child-mbox-flag / "\Subscribed" / "\Remote"
 mbx-list-sflag =/  "\NonExistent"
 mbox-or-pat =  list-mailbox / patterns
 option-extension =  (option-standard-tag / option-vendor-tag)
             [SP option-value]

Leiba & Melnikov Standards Track [Page 21] RFC 5258 IMAP4 LIST Command Extensions June 2008

 option-standard-tag =  atom
             ; an option defined in a Standards Track or
             ; Experimental RFC
 option-val-comp =  astring /
             option-val-comp *(SP option-val-comp) /
             "(" option-val-comp ")"
 option-value =  "(" option-val-comp ")"
 option-vendor-tag =  vendor-token "-" atom
             ; a vendor-specific option, non-standard
 patterns =  "(" list-mailbox *(SP list-mailbox) ")"
 return-option =  "SUBSCRIBED" / "CHILDREN" / option-extension
 tagged-ext-comp =  astring /
             tagged-ext-comp *(SP tagged-ext-comp) /
             "(" tagged-ext-comp ")"
             ; Extensions that follow this general
             ; syntax should use nstring instead of
             ; astring when appropriate in the context
             ; of the extension.
             ; Note that a message set or a "number"
             ; can always be represented as an "atom".
             ; A URL should be represented as
             ; a "quoted" string.
 tagged-ext-simple =  sequence-set / number
 tagged-ext-val =  tagged-ext-simple /
             "(" [tagged-ext-comp] ")"

7. Internationalization Considerations

 The LIST command selection option types defined in this specification
 involve simple tests of mailbox properties.  However, future
 extensions to LIST-EXTENDED may define selection options that do more
 sophisticated tests.  In the case of a test that requires matching
 text, in the presence of the COMPARATOR [I18N] extension, the active
 comparator must be used to do comparisons.  Such LIST-EXTENDED
 extensions MUST indicate in their specification the interaction with
 the COMPARATOR [I18N] extension.

Leiba & Melnikov Standards Track [Page 22] RFC 5258 IMAP4 LIST Command Extensions June 2008

8. Security Considerations

 This document describes syntactic changes to the specification of the
 IMAP4 commands LIST, LSUB, RLIST, and RLSUB, and the modified LIST
 command has the same security considerations as those commands.  They
 are described in [IMAP4] and [MBRef].
 The Child Mailbox Extension provides a client a more efficient means
 of determining whether a particular mailbox has children.  If a
 mailbox has children, but the currently authenticated user does not
 have access to any of them, the server SHOULD respond with a
 \HasNoChildren attribute.  In many cases, however, a server may not
 be able to efficiently compute whether a user has access to any child
 mailbox.  If such a server responds with a \HasChildren attribute,
 when in fact the currently authenticated user does not have access to
 any child mailboxes, potentially more information is conveyed about
 the mailbox than intended.  In most situations, this will not be a
 security concern, because if information regarding whether a mailbox
 has children is considered sensitive, a user would not be granted
 access to that mailbox in the first place.
 The CHILDINFO extended data item has the same security considerations
 as the \HasChildren attribute described above.

9. IANA Considerations

9.1. Guidelines for IANA

 IANA has created two new registries for LIST-EXTENDED options and
 LIST-EXTENDED response data.  The templates and the initial
 registrations are detailed below.

9.2. Registration Procedure and Change Control

 Registration of a LIST-EXTENDED option is done by filling in the
 template in Section 9.3 and sending it via electronic mail to
 iana@iana.org.  Registration of a LIST-EXTENDED extended data item is
 done by filling in the template in Section 9.5 and sending it via
 electronic mail to iana@iana.org.  IANA has the right to reject
 obviously bogus registrations, but will perform no review of claims
 made in the registration form.
 A LIST-EXTENDED option/extended data item name that starts with "V-"
 is reserved for vendor-specific options/extended data items.  All
 options, whether they are vendor specific or global, should be
 registered with IANA.  If a LIST-EXTENDED extended data item is
 returned as a result of requesting a particular LIST-EXTENDED option,

Leiba & Melnikov Standards Track [Page 23] RFC 5258 IMAP4 LIST Command Extensions June 2008

 the name of the option SHOULD be used as the name of the
 LIST-EXTENDED extended data item.
 Each vendor-specific option/extended data item MUST start with its
 vendor-token ("vendor prefix").  The vendor-token MUST be registered
 with IANA, using the [ACAP] vendor subtree registry.
 Standard LIST-EXTENDED option/extended data item names are case
 insensitive.  If the vendor prefix is omitted from a vendor-specific
 LIST-EXTENDED option/extended data item name, the rest is case
 insensitive.  The vendor prefix itself is not case sensitive, as it
 might contain non-ASCII characters.  While the registration
 procedures do not require it, authors of
 LIST-EXTENDED options/extended data items are encouraged to seek
 community review and comment whenever that is feasible.  Authors may
 seek community review by posting a specification of their proposed
 mechanism as an
 Internet-Draft.  LIST-EXTENDED option/extended data items intended
 for widespread use should be standardized through the normal IETF
 process, when appropriate.
 Comments on registered LIST-EXTENDED options/extended response data
 should first be sent to the "owner" of the mechanism and/or to the
 IMAPEXT WG mailing list.  Submitters of comments may, after a
 reasonable attempt to contact the owner, request IANA to attach their
 comment to the registration itself.  If IANA approves of this, the
 comment will be made accessible in conjunction with the registration
 LIST-EXTENDED options/extended response data itself.
 Once a LIST-EXTENDED registration has been published by IANA, the
 author may request a change to its definition.  The change request
 follows the same procedure as the registration request.
 The owner of a LIST-EXTENDED registration may pass responsibility for
 the registered option/extended data item to another person or agency
 by informing IANA; this can be done without discussion or review.
 The IESG may reassign responsibility for a LIST-EXTENDED
 option/extended data item.  The most common case of this will be to
 enable changes to be made to mechanisms where the author of the
 registration has died, has moved out of contact, or is otherwise
 unable to make changes that are important to the community.
 LIST-EXTENDED registrations may not be deleted; mechanisms that are
 no longer believed appropriate for use can be declared OBSOLETE by a
 change to their "intended use" field.  Such LIST-EXTENDED
 options/extended data items will be clearly marked in the lists
 published by IANA.

Leiba & Melnikov Standards Track [Page 24] RFC 5258 IMAP4 LIST Command Extensions June 2008

 The IESG is considered to be the owner of all LIST-EXTENDED
 options/extended data items that are on the IETF standards track.

9.3. Registration Template for LIST-EXTENDED Options

 To: iana@iana.org
 Subject: Registration of LIST-EXTENDED option X
 LIST-EXTENDED option name:
 LIST-EXTENDED option type: (One of SELECTION or RETURN)
 Implied return options(s), if the option type is SELECTION: (zero or
 more)
 LIST-EXTENDED option description:
 Published specification (optional, recommended):
 Security considerations:
 Intended usage:
 (One of COMMON, LIMITED USE, or OBSOLETE)
 Person and email address to contact for further information:
 Owner/Change controller:
 (Any other information that the author deems interesting may be added
 below this line.)

9.4. Initial LIST-EXTENDED Option Registrations

 The LIST-EXTENDED option registry has been populated with the
 following entries:
 1.  To: iana@iana.org
     Subject: Registration of LIST-EXTENDED option SUBSCRIBED
     LIST-EXTENDED option name: SUBSCRIBED
     LIST-EXTENDED option type: SELECTION
     Implied return options(s): SUBSCRIBED
     LIST-EXTENDED option description: Causes the LIST command to list
     subscribed mailboxes, rather than the actual mailboxes.

Leiba & Melnikov Standards Track [Page 25] RFC 5258 IMAP4 LIST Command Extensions June 2008

     Published specification: RFC 5258, Section 3.
     Security considerations: RFC 5258, Section 8.
     Intended usage: COMMON
     Person and email address to contact for further information:
     Alexey Melnikov <Alexey.Melnikov@isode.com>
     Owner/Change controller: iesg@ietf.org
 2.  To: iana@iana.org
     Subject: Registration of LIST-EXTENDED option REMOTE
     LIST-EXTENDED option name: REMOTE
     LIST-EXTENDED option type: SELECTION
     Implied return options(s): (none)
     LIST-EXTENDED option description: Causes the LIST command to
     return remote mailboxes as well as local ones, as described in
     RFC 2193.
     Published specification: RFC 5258, Section 3.
     Security considerations: RFC 5258, Section 8.
     Intended usage: COMMON
     Person and email address to contact for further information:
     Alexey Melnikov <Alexey.Melnikov@isode.com>
     Owner/Change controller: iesg@ietf.org
 3.  To: iana@iana.org
     Subject: Registration of LIST-EXTENDED option SUBSCRIBED
     LIST-EXTENDED option name: SUBSCRIBED
     LIST-EXTENDED option type: RETURN
     LIST-EXTENDED option description: Causes the LIST command to
     return subscription state.
     Published specification: RFC 5258, Section 3.
     Security considerations: RFC 5258, Section 8.

Leiba & Melnikov Standards Track [Page 26] RFC 5258 IMAP4 LIST Command Extensions June 2008

     Intended usage: COMMON
     Person and email address to contact for further information:
     Alexey Melnikov <Alexey.Melnikov@isode.com>
     Owner/Change controller: iesg@ietf.org
 4.  To: iana@iana.org
     Subject: Registration of LIST-EXTENDED option RECURSIVEMATCH
     LIST-EXTENDED option name: RECURSIVEMATCH
     LIST-EXTENDED option type: SELECTION
     Implied return options(s): (none)
     LIST-EXTENDED option description: Requests that CHILDINFO
     extended data item (childinfo-extended-item) is to be returned.
     Published specification: RFC 5258, Section 3.
     Security considerations: RFC 5258, Section 8.
     Intended usage: COMMON
     Person and email address to contact for further information:
     Alexey Melnikov <Alexey.Melnikov@isode.com>
     Owner/Change controller: iesg@ietf.org
 5.  To: iana@iana.org
     Subject: Registration of LIST-EXTENDED option CHILDREN
     LIST-EXTENDED option name: CHILDREN
     LIST-EXTENDED option type: RETURN
     LIST-EXTENDED option description: Requests mailbox child
     information.
     Published specification: RFC 5258, Section 3 and Section 4.
     Security considerations: RFC 5258, Section 8.
     Intended usage: COMMON
     Person and email address to contact for further information:
     Alexey Melnikov <Alexey.Melnikov@isode.com>

Leiba & Melnikov Standards Track [Page 27] RFC 5258 IMAP4 LIST Command Extensions June 2008

     Owner/Change controller: iesg@ietf.org

9.5. Registration Template for LIST-EXTENDED Extended Data Item

 To: iana@iana.org
 Subject: Registration of X LIST-EXTENDED extended data item
 LIST-EXTENDED extended data item tag:
 LIST-EXTENDED extended data item description:
 Which LIST-EXTENDED option(s) (and their types) causes this extended
 data item to be returned (if any):
 Published specification (optional, recommended):
 Security considerations:
 Intended usage:
 (One of COMMON, LIMITED USE, or OBSOLETE)
 Person and email address to contact for further information:
 Owner/Change controller:
 (Any other information that the author deems interesting may be added
 below this line.)

9.6. Initial LIST-EXTENDED Extended Data Item Registrations

 The LIST-EXTENDED extended data item registry has been populated with
 the following entries:
 1.  To: iana@iana.org
     Subject: Registration of CHILDINFO LIST-EXTENDED extended data
     item
     LIST-EXTENDED extended data item tag: CHILDINFO
     LIST-EXTENDED extended data item description: The CHILDINFO
     extended data item describes the selection criteria that has
     caused it to be returned and indicates that the mailbox has one
     or more child mailboxes that match the selection criteria.
     Which LIST-EXTENDED option(s) (and their types) causes this
     extended data item to be returned (if any): RECURSIVEMATCH
     selection option

Leiba & Melnikov Standards Track [Page 28] RFC 5258 IMAP4 LIST Command Extensions June 2008

     Published specification: RFC 5258, Section 3.5.
     Security considerations: RFC 5258, Section 8.
     Intended usage: COMMON
     Person and email address to contact for further information:
     Alexey Melnikov <Alexey.Melnikov@isode.com>
     Owner/Change controller: iesg@ietf.org

10. Acknowledgements

 Mike Gahrns and Raymond Cheng of Microsoft Corporation originally
 devised the Child Mailbox Extension and proposed it in 1997; the
 idea, as well as most of the text in Section 4, is theirs.
 This document is the result of discussions on the IMAP4 and IMAPEXT
 mailing lists and is meant to reflect consensus of those groups.  In
 particular, Mark Crispin, Philip Guenther, Cyrus Daboo, Timo
 Sirainen, Ken Murchison, Rob Siemborski, Steve Hole, Arnt
 Gulbrandsen, Larry Greenfield, Dave Cridland, and Pete Maclean were
 active participants in those discussions or made suggestions to this
 document.

11. References

11.1. Normative References

 [ABNF]   Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
          Specifications: ABNF", STD 68, RFC 5234, January 2008.
 [ACAP]   Newman, C. and J. Myers, "ACAP -- Application Configuration
          Access Protocol", RFC 2244, November 1997.
 [I18N]   Newman, C., Gulbrandsen, A., and A. Melnikov, "Internet
          Message Access Protocol Internationalization", RFC 5255,
          June 2008.
 [IMAP4]  Crispin, M., "Internet Message Access Protocol - Version
          4rev1", RFC 3501, March 2003.
 [Kwds]   Bradner, S., "Key words for use in RFCs to Indicate
          Requirement Levels", RFC 2119, March 1997.
 [MBRef]  Gahrns, M., "IMAP4 Mailbox Referrals", RFC 2193,
          September 1997.

Leiba & Melnikov Standards Track [Page 29] RFC 5258 IMAP4 LIST Command Extensions June 2008

11.2. Informative References

 [CMbox]  Gahrns, M. and R. Cheng, "The Internet Message Action
          Protocol (IMAP4) Child Mailbox Extension", RFC 3348,
          July 2002.

Authors' Addresses

 Barry Leiba
 IBM T.J. Watson Research Center
 19 Skyline Drive
 Hawthorne, NY  10532
 US
 Phone: +1 914 784 7941
 EMail: leiba@watson.ibm.com
 Alexey Melnikov
 Isode Limited
 5 Castle Business Village
 36 Station Road
 Hampton, Middlesex  TW12 2BX
 UK
 EMail: Alexey.Melnikov@isode.com
 URI:   http://www.melnikov.ca/

Leiba & Melnikov Standards Track [Page 30] RFC 5258 IMAP4 LIST Command Extensions June 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 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, THE IETF TRUST 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.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Leiba & Melnikov Standards Track [Page 31]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5258.txt · Last modified: 2008/06/06 23:07 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki