IMAP Extensions Working Group B. Leiba
Internet Draft IBM T.J. Watson Research Center
A. Melnikov
Isode Limited
Expires February 2004 August 2004
IMAP4 LIST Command Extensions
draft-ietf-imapext-list-extensions-08.txt
Status of this Document
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This documents obsoletes RFC 3348 and updates RFC 2193.
Abstract
IMAP4 has two commands for listing mailboxes: LIST and LSUB. As we
have added extensions that have required specialized lists (see
[MboxRefer] for an example) 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.
1. 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 words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY" are
used in this document as specified in RFC 2119 [Keywords].
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 editorial comments/questions are enclosed like this.>>
2. Introduction and overview
The extensions to the LIST command will be accomplished by amending
the syntax to allow options to be specified. The list of options
will replace the several commands that are currently used to mix and
match the information requested. The new syntax is backward-
compatible, with no ambiguity: <<if the first word after the command
name begins with a parenthesis, the new syntax is being used; if it
does not, it's in the original syntax>>.
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 [MboxRefer]. We are also defining the mechanism to
request extended mailbox information, such as is described in the
"Child Mailbox Extension" [ChildMbox]. 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 "X-DRAFT-W08-LISTEXT" <<the capability name will change
upon publication as an RFC>>. The LISTEXT extension makes the
following changes to the IMAP4 protocol, which are described in
more details in sections 3 and 4 of this document:
a. defines new syntax for LIST command options.
b. extend LIST to allow for multiple mailbox patterns.
c. adds LIST command match options: SUBSCRIBED and REMOTE
d. adds LIST command return options: SUBSCRIBED, REMOTE, CHILDREN
and SUBMAILBOXES.
e. adds new mailbox flags "\NonExistent", "\PlaceHolder",
"\Subscribed", "\Remote", "\HasSubmailboxes",
"\HasChildren" and "\HasNoChildren".
2.1. General principals for returning LIST responses
This section outlines several principals that can be used by
implementors of this document to decide if a LIST response should be
returned, as well as how many responses and what kind of information
they may contain.
1) Exactly one LIST response should be returned for each mailbox
name which matches the canonical LIST pattern.
Server implementors must not assume that clients will be able to
assemble mailbox flags and other information returned in multiple
LIST responses.
<<The following will be removed if the \PlaceHolder flag is also removed:
2) There are only two reasons for including a matching mailbox name
in the responses to the LIST command:
a) the mailbox name also satisfies the selection criteria;
b) the mailbox name has at least one child mailbox that satisfies
the selection criteria, but doesn't match the canonical LIST
pattern. For more information on this case see the \PlaceHolder
flag description in Section 3.
>>
3) Flags 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. LIST Command Options
This extension updates the syntax of the LIST command to allow for multiple
mailbox patterns to be specified, if they are enclosed in parantheses.
A mailbox match a list of mailbox patterns, if it matches at least one
mailbox pattern.
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 match options) and an optional 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 match option
tells the server which mailboxes should be selected by the LIST operation.
The server should return information about all mailboxes that match any of the
"canonical LIST pattern" (as described above) and satisfy additional selection
criteria (if any) specified by the LIST match options. Let's call any such
mailbox a "matched mailbox". Note, that if multiple match options are specified,
the server MUST return information about intersection of mailboxes that satisfy
any single match option.
A LIST return option controls which information is returned for each matched
mailbox. Note, that some return options may cause the server to report
information about additional mailboxes (e.g. SUBMAILBOXES). If the client
has omitted return options, only flag information should be returned by the
server.
Both match 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 NO response.
This extension is identified by the capability string "X-DRAFT-W08-LISTEXT"
<<Note to the RFC editor: please update upon publication as above>>, <<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.
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 type of the data. Tags
MUST be registered with IANA, as described in section 8.5 of this
document. An example of such extended set might be
((tablecloth (("fringe" "lacy")("color" "white")))(X-Sample
"text"))
or...
((tablecloth ("fringe" "lacy"))(X-Sample "text" "and even more text"))
See the formal grammar, below, for the full syntatic details.
The server MAY return data in the extended fields that was not solicited
by the client. The client MUST ignore all extended fields it doesn't
recognize.
The LISTEXT capability defines several new mailbox flags.
The "\PlaceHolder" flag indicates that the designated mailbox does not
meet the selection criteria of the given LIST command, but that it
has one or more child mailbox that might (unspecified whether any,
all, or none match the canonical LIST pattern).
The LSUB command indicates this condition by using the "\NoSelect"
flag, but the LIST (SUBSCRIBED) command MUST NOT do that, since
"\NoSelect" retains its original meaning here. Further, the
"\PlaceHolder" flag is more general, in that it can be used with any
extended set of selection criteria.
The "\HasSubmailboxes" flag indicates that the designated mailbox meets
the selection criteria of the given LIST command and also has one or more child
mailbox that might (unspecified whether any, all, or none match the canonical
LIST pattern).
Absence of both \PlaceHolder and \HasSubmailboxes means that the mailbox
meets the selection criterion, but doesn't have any children that also
meet the selection criterion and don't match the canonical LIST pattern.
However, absence of both \PlaceHolder and \HasSubmailboxes doesn't tell
whether there are any children that meet the selection criterion and match
the canonical LIST pattern.
<<We probably need an example to illustrate this>>
The SUBMAILBOXES return option described below REQUIRES that the "\Placeholder"
and the "\HasSubmailboxes" flags be accurately computed.
The "\Placeholder"/""\HasSubmailboxes" flag implies "\HasChildren".
The "\NonExistent" flag indicates that a mailbox does not actually exist.
Note that this flag is not meaningful by itself, as mailboxes 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 also satisfy the selection criteria
b) the mailbox has at least one child mailbox that satisfies the selection
criteria, but doesn't match the canonical LIST pattern.
In practice this means that the "\NonExistent" flag is usually returned
with one or more of \PlaceHolder/\HasSubmailboxes, \Subscribed, \Remote
(see there description below).
The "\NonExistent" flag implies "\NoSelect".
The "\NonExistent" flag MUST be supported and MUST be accurately computed.
The following table summarizes when \NonExistent, \PlaceHolder or
\HasSubmailboxes flags are to be returned:
+------+------------+---------------------+--------------------------------+
|exists| meets the | has a child that | returned |
| | selection | meets the selection | LISTEXT flags |
| | criteria | criteria | |
+------+------------+---------------------+--------------------------------+
| no | no | no | no LIST response returned |
| yes | no | no | no LIST response returned |
| no | yes | no | (\NonExistent) |
| yes | yes | no | () |
| no | no | yes | (\NonExistent \PlaceHolder) |
| yes | no | yes | (\PlaceHolder) |
| no | yes | yes | (\NonExistent \HasSubmailboxes)|
| yes | yes | yes | (\HasSubmailboxes) |
+------+------------+---------------------+--------------------------------+
The match options defined in this specification are
SUBSCRIBED - causes the LIST command to list subscribed
mailboxes, rather than the actual 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 flags as returned by this
option, compared with what is returned by LSUB. With the
latter, the flags returned may not reflect the actual flag
status on the mailbox, and the \NoSelect flag has a special
meaning (it indicates that this mailbox is not, itself,
subscribed, but that it has child mailboxes that are). With
the SUBSCRIBED match option described here, the flags 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 flag, "\Subscribed" that
indicates that a mailbox is subscribed to. The "\Subscribed"
flag MUST be supported and MUST be accurately computed
when the SUBSCRIBED match option is specified.
<<Note, that the SUBSCRIBED match 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 [MboxRefer]. This option
is intended to replace the RLIST command and, in conjunction
with the SUBSCRIBED match option, the RLSUB command.
This option defines a new mailbox flag, "\Remote", that
indicates that a mailbox is a remote mailbox. The "\Remote"
flag MUST be accurately computed when the REMOTE option is
specified.
<<Note, that the REMOTE match option implies the REMOTE
return option (see below).>>
The return options defined in this specification are
SUBSCRIBED - causes the LIST command to return subscription
state for all matching <<mailboxes?>>. The "\Subscribed"
flag MUST be supported and MUST be accurately computed
when the SUBSCRIBED return option is specified.
REMOTE - causes the LIST command to show if the matching <<mailbox>>
is local or remote. The "\Remote" flag MUST be accurately computed
when the REMOTE return option is specified.
Note, that a server implementation that doesn't support
any remote mailboxes is compliant with this specification
as long as it accepts and ignores the REMOTE return option.
CHILDREN - Requests mailbox child information as originally
proposed in [ChildMbox]. See section 4, below, for details.
This option MUST be accepted by all servers, however it MAY
be ignored.
SUBMAILBOXES - when this option is specified, the "\Placeholder"
and the "\HasSubmailboxes" flags MUST be accurate. This might
force the server to return information for additional mailboxes.
Note, that even it SUBMAILBOXES option is specified, the client
still must be able to handle a case when a "\PlaceHolder"/
"\HasSubmailboxes" is returned and there are no submailboxes
that meet the selection criteria of the given LIST command,
as they can be deleted/renamed after the LIST response was sent,
but before the client had a chance to access them.
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 [ChildMbox]. 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, or MAY ignore the option entirely.
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
clicked the hierarchy list is expanded to show the child mailboxes.
The Child Mailbox Extension provides a mechanism for a client to
efficiently determine if a particular mailbox has children, without
issuing a LIST "" * or a LIST "" % for each mailbox name.
The Child Mailbox Extension defines two new attributes that MAY be
returned within a LIST response: \HasChildren and \HasNoChildren.
While 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 SHOULD 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 permissions 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 all child mailboxes. As
such a client MUST be prepared to accept the \HasChildren
attribute as a hint. That is, a mailbox MAY be flagged with the
\HasChildren attribute, but no child mailboxes will appear in
the LIST response.
\HasNoChildren - The presence of this attribute indicates that the
mailbox has NO child mailboxes that are accessible to the
currently authenticated user.
In some instances a server that supports the Child Mailbox Extension
might not be able to determine whether a mailbox has children. For
example it may have difficulty determining whether there are child
mailboxes when LISTing mailboxes while operating in a particular
namespace.
In these cases, a server MAY exclude both the \HasChildren and
\HasNoChildren attributes in the LIST response. As such, a client
can not make any assumptions about whether a mailbox has children
based upon the absence of a single attribute. In particular, some
servers may not be able to combine the SUBSCRIBED match option
and CHILDREN return option. Such servers MUST honour the SUBSCRIBED
match option, and they will simply ignore the CHILDREN return option
if both are requested. It is an error for the server to return both a
\HasChildren and a \HasNoChildren attribute in a 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.
5. Examples
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
In the next example, we'll see the subscribed mailboxes. This is
similar, but not equivalent, to <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 (\PlaceHolder) "/" "Fruit"
S: * LIST (\Subscribed) "/" "Fruit/Banana"
S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach"
S: * LIST (\Subscribed \HasSubmailboxes) "/" "Vegetable"
S: * LIST (\Subscribed) "/" "Vegetable/Broccoli"
S: A02 OK done
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 sub-mailboxes (children) and which do
not. Note that it's not necessary for the server to return the
\HasNoChildren flag for the inbox, because the \NoInferiors flag
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
In this example we see more mailboxes, which reside on another server
to which we may obtain referrals. This is similar to the command
<RLIST "" "%">. Note that in the case of the remote mailboxes, the
server might or might not be able to include CHILDREN information;
it includes it if it can, and omits it if it can't.
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
The following example also requests the server to include mailboxes,
which reside on another server. The server returns information about
all mailboxes which are subscribed. This is similar to the command
<RLSUB "" "%">. We also see the mixing of two match 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
The following example requests the server to include mailboxes,
which reside on another server. The server is requested to return
subscription information for all returned mailboxes. This is different
from the example above. <<Can we say that the output is a superset
of the output in the previous example? What about nonexistent
"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 (\Subscribed \NonExistent) "/" "Fruit/Peach">>
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
In the following example the client has specified multiple mailbox
patterns.
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
6. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) as described in [ABNF]. Terms not defined here are taken
from [IMAP4]. "vendor-token" is defined in [ACAP].
child-mbox-flag = "\HasChildren" / "\HasNoChildren"
; flags for Child Mailbox Extension, at most one
; possible per LIST response
list = "LIST" [SP list-match-opts] SP mailbox SP mbox_or_pat
[SP list-return-opts]
list-match-opts = "(" [match-option *(SP match-option)] ")"
; list match options, e.g. REMOTE
list-return-opts = "RETURN" SP "(" [return-option *(SP return-option)] ")"
; list return options, e.g. CHILDREN
mailbox-list = "(" [mbx-list-flags] ")" SP
(DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox
[SP mbox-list-extended]
mbox-list-extended = "(" [mbox-list-extended-item
*(SP mbox-list-extended-item)] ")"
mbox-list-extended-item = "(" mbox-list-extended-item-data ")"
mbox-list-extended-item-data = mbox-list-extended-item-tag SP nstring-list
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 section
; 8.5 of this document.
mbox_or_pat = list-mailbox / patterns
patterns = "(" list-mailbox *(list-mailbox) ")"
eitem-vendor-tag = vendor-tag
; a vendor specific tag for extended list data
eitem-standard-tag = atom
; a tag for extended list data defined in a Standard
; Track or Experimental RFC.
nstring-list = nstring /
"(" [nstring-list *(SP nstring-list)] ")"
;; a recursive list definition
mbox-list-oflag = child-mbox-flag / "\NonExistent" / "\PlaceHolder" /
"\HasSubmailboxes" / "\Subscribed" / "\Remote"
match-option = "SUBSCRIBED" / "REMOTE" / option-extension
; An option registration template is described in section
; 8.3 of this document.
return-option = "SUBSCRIBED" / "REMOTE" / "CHILDREN" / "SUBMAILBOXES" /
option-extension
option-extension = option-vendor-tag / option-standard-tag
option-vendor-tag = vendor-tag
; a vendor specific option
option-standard-tag= atom
; an option defined in a Standard Track or
; Experimental RFC
vendor-tag = vendor-token "-" atom
7. 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 [MboxRefer].
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 all child
mailboxes. 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.
8. IANA Considerations
8.1. Guidelines for IANA
It is requested that IANA creates two new registries for LISTEXT
options and LISTEXT extended response data. The templates and
the initial registrations are detailed below.
8.2. Registration procedure and Change control
Registration of a LISTEXT option is done by filling in the template
in section 8.3 and sending it via electronic mail to <iana@iana.org>.
Registration of a LISTEXT extended data item is done by filling in the
template in section 8.5 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 LISTEXT 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 LISTEXT extended data item is returned as a result of requesting
a particular LISTEXT option, the name of the option SHOULD be used
as the name of the LISTEXT extended data item.
Each vendor specific options/extended data item MUST start with their
vendor-token ("vendor prefix"). The vendor-token MUST be registered
with IANA, using the [ACAP] vendor subtree registry.
Standard LISTEXT option/extended data item names are case insensitive.
If the vendor prefix is omitted from a vendor specific LISTEXT
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 LISTEXT
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. LISTEXT options/extended data items intended for widespread use
should be standardized through the normal IETF process, when appropriate.
Comments on registered LISTEXT 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 LISTEXT options/
extended response data itself.
Once a LISTEXT 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 LISTEXT 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 LISTEXT 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, moved out
of contact or is otherwise unable to make changes that are important
to the community.
LISTEXT registrations may not be deleted; mechanisms which are
no longer believed appropriate for use can be declared OBSOLETE by a
change to their "intended use" field; such LISTEXT options/extended data
items will be clearly marked in the lists published by IANA.
The IESG is considered to be the owner of all LISTEXT options/extended data items
which are on the IETF standards track.
8.3. Registration template for LISTEXT options
To: iana@iana.org
Subject: Registration of LISTEXT option X
LISTEXT option name:
LISTEXT option type: (One of MATCH or RETURN)
<<Implied return options(s) if the option type is MATCH?>>
LISTEXT option description:
Published specification (optional, recommended):
Security considerations:
Intended usage:
(One of COMMON, LIMITED USE or OBSOLETE)
Person & email address to contact for further information:
Owner/Change controller:
(Any other information that the author deems interesting may be
added below this line.)
8.4. Initial LISTEXT option registrations
It is requested that the LISTEXT option registry is being populated
with the following entries:
1)
To: iana@iana.org
Subject: Registration of LISTEXT option SUBSCRIBED
LISTEXT option name: SUBSCRIBED
LISTEXT option type: MATCH
LISTEXT option description: Causes the LIST command to list
subscribed mailboxes, rather than the actual mailboxes.
Published specification : this RFC, section 3.
Security considerations: this RFC, section 7.
Intended usage: COMMON
Person & email address to contact for further information:
Alexey Melnikov <Alexey.Melnikov@isode.com>
Owner/Change controller: IESG <iesg@ietf.org>
2)
To: iana@iana.org
Subject: Registration of LISTEXT option REMOTE
LISTEXT option name: REMOTE
LISTEXT option type: MATCH
LISTEXT option description: causes the LIST command to return
remote mailboxes as well as local ones, as described in
RFC 2193.
Published specification : this RFC, section 3.
Security considerations: this RFC, section 7.
Intended usage: COMMON
Person & email address to contact for further information:
Alexey Melnikov <Alexey.Melnikov@isode.com>
Owner/Change controller: IESG <iesg@ietf.org>
3)
To: iana@iana.org
Subject: Registration of LISTEXT option SUBSCRIBED
LISTEXT option name: SUBSCRIBED
LISTEXT option type: RETURN
LISTEXT option description: Causes the LIST command to return
subscription state.
Published specification : this RFC, section 3.
Security considerations: this RFC, section 7.
Intended usage: COMMON
Person & email address to contact for further information:
Alexey Melnikov <Alexey.Melnikov@isode.com>
Owner/Change controller: IESG <iesg@ietf.org>
4)
To: iana@iana.org
Subject: Registration of LISTEXT option REMOTE
LISTEXT option name: REMOTE
LISTEXT option type: MATCH
LISTEXT option description: causes the LIST command to return
if the mailbox is local or remote, as described in
RFC 2193.
Published specification : this RFC, section 3.
Security considerations: this RFC, section 7.
Intended usage: COMMON
Person & email address to contact for further information:
Alexey Melnikov <Alexey.Melnikov@isode.com>
Owner/Change controller: IESG <iesg@ietf.org>
5)
To: iana@iana.org
Subject: Registration of LISTEXT option SUBMAILBOXES
LISTEXT option name: SUBMAILBOXES
LISTEXT option type: RETURN
LISTEXT option description: Requests that \Placeholder/
\HasSubmailboxes flags are to be accurately computed.
Published specification : this RFC, sections 3.
Published specification : this RFC
Security considerations: this RFC, section 7.
Intended usage: COMMON
Person & email address to contact for further information:
Alexey Melnikov <Alexey.Melnikov@isode.com>
Owner/Change controller: IESG <iesg@ietf.org>
6)
To: iana@iana.org
Subject: Registration of LISTEXT option CHILDREN
LISTEXT option name: CHILDREN
LISTEXT option type: RETURN
LISTEXT option description: Requests mailbox child information.
Published specification : this RFC, sections 3 and 4.
Published specification : this RFC
Security considerations: this RFC, section 7.
Intended usage: COMMON
Person & email address to contact for further information:
Alexey Melnikov <Alexey.Melnikov@isode.com>
Owner/Change controller: IESG <iesg@ietf.org>
8.5. Registration template for LISTEXT extended data item
To: iana@iana.org
Subject: Registration of LISTEXT extended data item X
LISTEXT extended data item tag:
LISTEXT extended data item description:
Which LISTEXT 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 & 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. References
9.1. Normative References
[Keywords] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March 1997.
[ABNF] Crocker, D., and Overell, P. "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[IMAP4] Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 3501, University of Washington, March 2003.
[MboxRefer] Gahrns, M., "IMAP4 Mailbox Referrals", RFC 2193,
Microsoft Corporation, September 1997.
[ChildMbox] Gahrns, M. & Cheng, R., "IMAP4 Child Mailbox Extension",
RFC 3348, Microsoft Corporation, July 2002.
[ACAP] Newman, C. and J. Myers, "ACAP -- Application
Configuration Access Protocol", RFC 2244, November 1997.
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 mailing list
and is meant to reflect consensus of this group. In particular,
Mark Crispin, Philip Guenther, Cyrus Daboo, Timo Sirainen,
Ken Murchison, Rob Siemborski, Steve Hole, Arnt Gulbrandsen, Larry
Greenfield and Pete Maclean were active participants
in this discussion or made suggestions to this document.
11. Author's Address
Barry Leiba
IBM T.J. Watson Research Center
30 Saw Mill River Road
Hawthorne, NY 10532
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/
12. IPR Disclosure Acknowledgement
By submitting this Internet-Draft, we certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which we become aware will be disclosed, in accordance with
RFC 3668.
13. 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.
14. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by
the Internet Society.
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