Network Working Group Alexey Melnikov
Internet-Draft Isode Ltd.
Intended Status: Proposed Standard Arnt Gulbrandsen
Oryx Mail Systems GmbH
Curtis King
Isode Ltd.
March 24, 2008
The IMAP NOTIFY Extension
draft-ietf-lemonade-imap-notify-05.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-
Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft expires in September 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document defines an IMAP extension which allows a client to
request specific kinds of unsolicited notifications for specified
mailboxes, such as messages being added to or deleted from
King, et al. Expires September 2008 FF[Page 1]
Internet-draft March 2008
mailboxes.
[[Add Updates: RFC-CONTEXT to the headers]]
1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Formal syntax is defined by [RFC5234] as extended by [RFC3501] and
[RFC4466].
The acronym MSN stands for Message Sequence Numbers (see Section
2.3.1.2 of [RFC3501]).
Example lines prefaced by "C:" are sent by the client and ones
prefaced by "S:" by the server. "[...]" means elision.
2. Overview and rationale
The IDLE command (defined in [RFC2177]) provides a way for the
client to go into a mode where the IMAP server pushes notifications
about IMAP mailstore events for the selected mailbox. However, the
IDLE extension doesn't restrict or control which server events can
be sent, or what information the server sends in response to each
event. Also, IDLE only applies to the selected mailbox, thus
requiring an additional TCP connection per mailbox.
This document defines an IMAP extension that allows clients to
express their preferences about unsolicited events generated by the
server. The extension allows clients to only receive events they
are interested in, while servers know that they don't need to go
into effort of generating certain types of untagged responses.
Without the NOTIFY command defined in this document, an IMAP server
will only send information about mailstore changes to the client in
the following cases:
- as the result of a client command (e.g. FETCH responses to
a FETCH or STORE command),
- unsolicited responses sent just before the end of a command
(e.g. EXISTS or EXPUNGE) as the result of changes in other
sessions, and
- during an IDLE command.
The NOTIFY command extends what information may be returned in those
King, et al. Expires September 2008 FF[Page 2]
Internet-draft March 2008
last two cases, and also permits and requires the server to send
information about updates between command. The NOTIFY command also
allows for the client to extend what information is sent unsolicited
about the selected mailbox, and to request some update information
to be sent regarding other mailboxes.
For the new messages delivered to or appended to the selected
mailbox, the NOTIFY command can be used to request that a set of
attributes be sent to the client in an unsolicited FETCH response.
This allows a client to be passive recipient of events and new mail,
and be able to maintain full synchronisation without having to issue
any subsequent commands except to modify the state of the mailbox on
the server.
Some mobile clients, however, may want mail "pushed" only for mail
that matches a SEARCH pattern. To meet that need [CONTEXT] is
augmented by this document to extend the UPDATE return option to
specify a list of fetch-atts to be returned when a new message is
delivered or appended in another session.
[[RFC-Editor: Please delete the following before publication:
Comments regarding this draft may be sent either to the
lemonade@ietf.org mailing list or to the authors.]]
3. The NOTIFY extension
IMAP servers which support this extension advertise the X-DRAFT-
W05-NOTIFY capability. This extension adds the NOTIFY command as
defined in Section 5.1.
A server implementing this extension is not required to implement
LIST-EXTENDED [LISTEXT], even though a NOTIFY compliant server must
be able to return extended LIST responses defined in [LISTEXT].
[[RFC-Editor: Should QRESYNC be a required dependency for this
extension?]]
3.1. The NOTIFY Command
Arguments: "SET"
optional STATUS indicator
Mailboxes to be watched
Events about which to notify the client
King, et al. Expires September 2008 FF[Page 3]
Internet-draft March 2008
Or
Arguments: "NONE"
Responses: Possibly untagged STATUS responses (for SET)
Result: OK - The server will notify the client as requested.
NO - Unsupported notify event, NOTIFY too complex or
expensive, etc.
BAD - Command unknown, invalid, unsupported or unknown
arguments.
The NOTIFY command informs the server that the client listens for
event notifications all the time (even when no command is in
progress) and requests the server to notify it about the specified
set of events. The NOTIFY command has two forms. NOTIFY NONE
specifies that the client is not interested in any kind of event
happening on the server. NOTIFY SET replaces the current list of
interesting events with a new list of events.
Until the NOTIFY command is used for the first time, the server only
sends notifications while a command is being processed, and notifies
the client about these events on the selected mailbox: (see section
5 for definitions): MessageNew, MessageExpunge, FlagChange. It does
not notify the client about any events on other mailboxes.
The effect of a successful NOTIFY command lasts until the next
NOTIFY command, or until the IMAP connection is closed.
A successful NOTIFY SET command MUST cause the server to immediately
return any accumulated changes to the currently selected mailbox (if
any), such as flag changes, new or expunged messages. This is
equivalent to NOOP command being issued by the client just before
the NOTIFY SET command.
The NOTIFY SET command can request notifications of changes to the
selected mailbox, whatever it may be at the time the notifications
are being generated. This is done by specifying the SELECTED mailbox
selector (see Section 6.1) in the NOTIFY SET command. The client
can also request notifications on other mailboxes by name or by a
limited mailbox pattern match. The notifications returned for the
currently selected mailbox will be those specified by the SELECTED
mailbox specifier, even if the selected mailbox also appears by name
in the command.
If the NOTIFY command enables MessageNew, MessageExpunge,
AnnotationChange or FlagChange notification for a mailbox other than
SELECTED, and the client has specified the STATUS indicator
parameter, then the server MUST send a STATUS response for that
King, et al. Expires September 2008 FF[Page 4]
Internet-draft March 2008
mailbox before NOTIFY's tagged OK. If MessageNew is enabled, the
STATUS response MUST contain MESSAGES, UIDNEXT and UIDVALIDITY. If
MessageExpunge is enabled, the STATUS response MUST contain
MESSAGES. If either AnnotationChange or FlagChange are included and
the server also supports CONDSTORE [RFC4551] and/or QRESYNC
[QRESYNC] extension, the STATUS response MUST contain UIDVALIDITY
and HIGHESTMODSEQ. Absence of the STATUS indicator parameter allows
the client to avoid the additional STATUS responses. This might be
useful if the client has already retrieved this information before
issuing the NOTIFY command.
Clients are advised to limit the number of mailboxes used with
NOTIFY. Particularly, if a client asks for events for all accessible
mailboxes, the server may swamp the client with updates about shared
mailboxes. This wastes both server and network resources. For
each mailbox specified, the server verifies that the client has
access using the following test:
- If the name does not refer to an existing mailbox, the server MUST
ignore it.
- If the name refers to a mailbox which the client can't LIST, the
server MUST ignore it. For a server that implements [RFC4314] this
means that if the client that doesn't have the 'l' (lookup) right
for the name, then the server MUST ignore the mailbox. This
behavior prevents dislosure on potentially confidential
information to clients which don't have rights to know it.
- If the name refers to a mailbox which the client can LIST (e.g. it
has the 'l' right from [RFC4314]), but doesn't have another right
required for processing of the specified event(s), then the server
MUST respond with an untagged extended LIST response containing
the \NoAccess name attribute.
The server SHOULD return the tagged OK response if the client has
access to at least one of the mailboxes specified in the current
list of interesting events. The server MAY return the tagged NO
response if the client has no access to any of the specified
mailboxes and no access can ever be granted in the future (e.g. the
client specified an event for 'Subtree Bar/Foo', 'Bar/Foo' doesn't
exist and LIST returns \Noinferiors for the parent 'Bar').
If the notification would be prohibitively expensive for the server
(e.g. "notify me of all flag changes in all mailboxes"), the server
MAY refuse the command with a tagged NO [NOTIFICATIONOVERFLOW]
response.
If the client requests information for events of an unsupported
King, et al. Expires September 2008 FF[Page 5]
Internet-draft March 2008
type, the server MUST refuse the command with a tagged NO response
(not a BAD). This response SHOULD contain the BADEVENT response
code, which MUST list names of all events supported by the server.
Here's an example:
S: * OK [CAPABILITY IMAP4REV1 NOTIFY]
C: a login bob alice
S: a OK Password matched
C: b notify set status (selected MessageNew (uid
body.peek[header.fields (from to subject)]) MessageExpunge)
(subtree Lists MessageNew)
S: * STATUS Lists/Lemonade (UIDVALIDITY 4 UIDNEXT 9999 MESSAGES
500)
S: [...]
S: * STATUS Lists/Im2000 (UIDVALIDITY 901 UIDNEXT 1 MESSAGES 0)
S: b OK done
C: c select inbox
S: [...] (the usual 7-8 responses to SELECT)
S: c OK INBOX selected
(Time passes. A new message is delivered to mailbox
Lists/Lemonade.)
S: * STATUS Lists/Lemonade (UIDVALIDITY 4 UIDNEXT 10000
MESSAGES 501)
(Time passes. A new message is delivered to inbox.)
S: * 127 FETCH (UID 127001 BODY[HEADER.FIELDS (From To
Subject)] {75}
S: Subject: Re: good morning
S: From: alice@example.org
S: To: bob@example.org
S:
S: )
(Time passes. The client decides it wants to know about
one more mailbox. As the client already knows
necessary STATUS information for all mailboxes below
the Lists mailbox and because "notify set status" would
cause STATUS responses for *all* mailboxes specified in
the NOTIFY command, including the ones for which the
client already knows STATUS information, the client
issues explicit STATUS request for the mailbox to be
added to the watch list, followed by the NOTIFY SET
without the STATUS parameter.)
C: d STATUS misc (UIDVALIDITY UIDNEXT MESSAGES)
S: * STATUS misc (UIDVALIDITY 1 UIDNEXT 999)
S: d STATUS completed
C: e notify set (selected MessageNew (uid
body.peek[header.fields (from to subject)]) MessageExpunge)
(subtree Lists MessageNew) (mailboxes misc MessageNew)
King, et al. Expires September 2008 FF[Page 6]
Internet-draft March 2008
S: e OK done
4. Interaction with the IDLE Command
If IDLE (as well as this extension) is supported, while processing
IDLE the server MUST send the same events as instructed by the
client using the NOTIFY command.
NOTIFY makes IDLE unnecessary for some clients. If a client does not
use MSNs and '*' in commands, it can request MessageExpunge and
MessageNew for the selected mailbox using the NOTIFY command instead
of entering the IDLE mode.
5. Event Types
Only some of the events in [MSGEVENT] can be expressed in IMAP, and
for some of them there are several possible ways to express the
event.
This section specifies the events which an IMAP server can notify an
IMAP client, and how.
The server SHOULD omit notifying the client if the event is caused
by this client. For example, if the client issues CREATE and has
requested MailboxName event that would cover the newly created
mailbox, the server SHOULD NOT notify the client of the MailboxName
change.
All event types described in this document require the 'l' and 'r'
rights (see [RFC4314]) on all observed mailboxes. Servers that
don't implement [RFC4314] should map the above rights to their
access control model.
If FlagChange event is specified, MessageNew and MessageExpunge MUST
also be specified by the client. Otherwise the server MUST respond
with the tagged BAD response.
If one of MessageNew or MessageExpunge is specified, the both events
MUST be specified. Otherwise the server MUST respond with the
tagged BAD response.
If the client instructs the server not to send MessageNew and
MessageExpunge for the selected mailbox, the server MUST still send
EXISTS and EXPUNGE responses as required by IMAP (see [RFC3501]
section 7). In other words, MessageExpunge instructs the server to
notify the client immediately, and the lack of MessageExpunge
King, et al. Expires September 2008 FF[Page 7]
Internet-draft March 2008
instructs the server to notify the client during execution of the
next command as specified in [RFC3501]. MessageNew is handled
similarly by the server.
5.1. FlagChange and AnnotationChange
If the flag and/or message annotation change happens in the selected
mailbox, the server MUST notify the client by sending an unsolicited
FETCH response, which MUST include UID and FLAGS/ANNOTATION FETCH
data items. It MAY also send new FLAGS and/or OK [PERMANENTFLAGS
...] responses.
If a search context is in effect as specified in [CONTEXT], an
ESEARCH ADDTO or ESEARCH REMOVEFROM will also be generated, if
appropriate. In this case, the FETCH response MUST precede the
ESEARCH response.
If the change happens in another mailbox, then the response depends
on whether CONDSTORE [RFC4551] and/or QRESYNC [QRESYNC] is being
used. If so, the server sends a STATUS (HIGHESTMODSEQ) response.
Note that whenever mailbox UIDVALIDITY changes, the server MUST also
include UIDVALIDITY in the STATUS response. If the number of
messages with \Seen flag changes, the server MAY also include the
UNSEEN in the STATUS response. If CONDSTORE/QRESYNC is not used and
the server choses not to include the UNSEEN, the server does not
notify the client. [[Open Issue: should there be a way to require
the server to return UNSEEN?]]
FlagChange covers the MessageRead, MessageTrash, FlagsSet and
FlagsClear events in [MSGEVENT].
Example in the selected mailbox:
S: * 99 FETCH (UID 9999 FLAGS ($Junk))
And in another, with CONDSTORE in use:
S: * STATUS Lists/Lemonade (HIGHESTMODSEQ 65666665)
5.2. MessageNew
This covers both MessageNew and MessageAppend in [MSGEVENT].
If the new/appended message is in the selected mailbox, the server
notifies the client by sending an unsolicited EXISTS response,
followed by an unsolicited FETCH response containing the information
requested by the client. A FETCH response SHOULD NOT be generated
for a new message created by the client on this particular
King, et al. Expires September 2008 FF[Page 8]
Internet-draft March 2008
connection, for instance as the result of an APPEND or COPY command
to the selected mailbox performed by the client itself. The server
MAY also send a RECENT response, if the server marks the message as
\Recent.
Note that a single EXISTS response can be returned for multiple
MessageAppend/MessageNew events.
If a search context is in effect as specified in [CONTEXT], an
ESEARCH ADDTO will also be generated, if appropriate. In this case,
the EXISTS response MUST precede the ESEARCH response. Both the
NOTIFY command and the SEARCH and SORT commands (see Section 7) can
specify attributes to be returned for new messages. These
attributes SHOULD be combined into a single FETCH response. The
server SHOULD avoid sending duplicate data. The FETCH response(s)
MUST follow any ESEARCH ADDTO responses.
If the new/appended message is in another mailbox, the server sends
an unsolicited STATUS (UIDNEXT MESSAGES) response for the relevant
mailbox. If CONDSTORE (defined in [RFC4551]) is in use, the
HIGHESTMODSEQ status data item MUST be included in the STATUS
response.
The client SHOULD NOT use FETCH attributes that implicitly set the
\seen flag, or that presuppose the existence of a given bodypart.
UID, MODSEQ, FLAGS, ENVELOPE, BODY.PEEK[HEADER.FIELDS... and
BODY/BODYSTRUCTURE may be the most useful attributes.
Note that if a client asks to be notified of MessageNew events, the
number of messages can increase at any time, and therefore the
client cannot refer to a specific message using the MSN/UID '*'.
Example in the selected mailbox:
S: * 444 EXISTS
S: * 444 FETCH (UID 9999)
And in another, without CONDSTORE:
S: * STATUS Lists/Lemonade (UIDNEXT 10002 MESSAGES 503)
5.3. MessageExpunge
If the expunged message(s) is/are in the selected mailbox, the
server notifies the client using EXPUNGE (or VANISHED, if [QRESYNC]
is supported by the server and enabled by the client).
If a search context is in effect as specified in [CONTEXT], an
ESEARCH REMOVEFROM will also be generated, if appropriate.
King, et al. Expires September 2008 FF[Page 9]
Internet-draft March 2008
If the expunged message(s) is/are in another mailbox, the server
sends an unsolicited STATUS (UIDNEXT MESSAGES) response for the
relevant mailbox. If CONDSTORE is being used, HIGHESTMODSEQ MUST be
included in the STATUS response.
Note that if a client requests MessageExpunge, the meaning of a MSN
can change at any time, so the client cannot use MSNs in commands
anymore. For example, such a client cannot use FETCH, but it has to
use UID FETCH. The meaning of '*' can also change when messages are
added or expunged. A client wishing to keep using MSNs MUST NOT
request the MessageExpunge event.
The MessageExpunge notification covers both MessageExpunge and
MessageExpire events from [MSGEVENT].
Example in the selected mailbox, without QRESYNC:
S: * 444 EXPUNGE
The same example in the selected mailbox, with QRESYNC:
S: * VANISHED 5444
And in another:
S: * STATUS misc (UIDNEXT 999 MESSAGES 554)
5.4. MailboxName
These notifications are sent if an affected mailbox name was created
(with CREATE), deleted (with DELETE) or renamed (with RENAME). For
a server that implements [RFC4314] granting or revocation of the 'l'
right to the current user on the affected mailbox MUST be considered
mailbox creation/deletion respectively. If a mailbox is created or
deleted, the mailbox itself and its parent are considered to be
affected.
The server notifies the client by sending an unsolicited LIST
response for each affected mailbox name. If, after the event, the
mailbox name does not refer to a mailbox accessible to the client,
the \Nonexistent flag MUST be included.
For each LISTable mailbox renamed, the server sends an extended LIST
response [LISTEXT] for the new mailbox name, containing the OLDNAME
extended data item with the old mailbox name. When a mailbox is
renamed, its children are renamed too. No additional MailboxName
events are sent for children in this case. When INBOX is renamed, a
new INBOX is assumed to be created. No MailboxName event must be
sent for INBOX in this case.
Example of a newly created mailbox (or granting of the 'l' right on
the mailbox):
King, et al. Expires September 2008 FF[Page 10]
Internet-draft March 2008
S: * LIST () "/" "NewMailbox"
And a deleted mailbox (or revocation of the 'l' right on the
mailbox):
S: * LIST (\NonExistent) "." "INBOX.DeletedMailbox"
Example of a renamed mailbox:
S: * LIST () "/" "NewMailbox" ("OLDNAME" ("OldMailbox"))
5.5. SubscriptionChange
The server notifies the client by sending an unsolicited LIST
responses for each affected mailbox name. If and only if the mailbox
is subscribed after the event, the \Subscribed attribute (see
[LISTEXT]) is included.
Example:
S: * LIST (\Subscribed) "/" "SubscribedMailbox"
5.6. MailboxMetadataChange
The server sends an unsolicited LIST response including METADATA (as
per Section 4.3.1 of [METADATA]). If possible, only the changed
metadata should be included, but if necessary, all metadata must be
included.
Example:
S: * LIST "/" "INBOX" (METADATA (/comment))
5.7. ServerMetadataChange
The server sends an unsolicited METADATA response (as per Section
4.5.2 of [METADATA]). Only the names of changed metadata entries
SHOULD be returned in such METADATA responses.
Example:
S: * METADATA (/comment)
5.8. Notification Overflow
If the server is unable or unwilling to deliver as many
notifications as it is being asked to, it may disable notifications
for some or all clients. It MUST notify these clients by sending an
King, et al. Expires September 2008 FF[Page 11]
Internet-draft March 2008
untagged "OK [NOTIFICATIONOVERFLOW]" response and behave as if a
NOTIFY NONE command had just been received.
Example:
S: * OK [NOTIFICATIONOVERFLOW] ...A comment can go here...
5.9. ACL Changes
Even if NOTIFY succeeds, it is still possible to lose access to the
mailboxes monitoried at a later time. If this happens, the server
MUST stop monitoring these mailboxes. If access is later granted,
the server MUST restart event monitoring.
The server SHOULD return the LIST response with the \NoAccess name
attribute if and when the mailbox loses the 'l' right. Simalarly,
the server SHOULD return the LIST response with no \NoAccess name
attribute, if the mailbox was previously reported as having
\NoAccess, and later on the 'l' right is granted.
6. Mailbox Specification
Mailboxes to be monitored can be specified in several different
ways.
Only 'selected' (section 6.1) matches the currently selected
mailbox. All other mailbox specifications affect other (non-
selected) mailboxes.
If for any given event type the client specifies monitoring of the
same mailbox several times (using the same or different mailbox
specifications), the first specification wins.
Note that for different event types different <event-group>s can
apply to the same mailbox. The following example demonstrates this.
In this example, MessageNew and MessageExpunge events are reported
for INBOX due to the first <event-group>. SubscriptionChange event
will also be reported for INBOX due to the second <event-group>.
C: a notify set (mailboxes INBOX (Messagenew messageExpunge))
(personal (SubscriptionChange))
A typical client that supports the NOTIFY extension would ask for
events on the selected mailbox and some named mailboxes.
In this example, the client asks for FlagChange events for all
King, et al. Expires September 2008 FF[Page 12]
Internet-draft March 2008
personal mailboxes except the selected mailbox:
C: a notify set (selected (Messagenew (uid flags)
messageExpunge)) (personal (MessageNew FlagChange
MessageExpunge))
6.1. Selected
Selected refers to the mailbox selected using either SELECT or
EXAMINE (see [RFC3501] section 6.3.1 and 6.3.2). When the IMAP
connection is not in selected state, selected does not refer to any
mailbox.
6.2. Personal
Personal refers to all selectable mailboxes in the user's personal
namespace(s).
6.3. Inboxes
Inboxes refers to all selectable mailboxes in the user's personal
namespace(s) to which messages may be delivered by an MDA (see
[EMAIL-ARCH], particularly section 4.3.3).
If the IMAP server cannot easily compute this set, it MUST treat
"inboxes" as equivalent to "personal".
6.4 Subscribed
Subscribed refers to all mailboxes subscribed by the user.
If the subscription list changes, the server MUST reevaluate the
list.
6.5 Subtree
Subtree is followed by a mailbox name or list of mailbox names. A
subtree refers to all selectable mailboxes which are subordinate to
the specified mailbox plus the mailbox itself.
6.6 Mailboxes
Mailboxes is followed by a mailbox name or a list of mailbox names.
King, et al. Expires September 2008 FF[Page 13]
Internet-draft March 2008
The server MUST NOT do wildcard expansion. This means there is no
special treatment for the LIST wildcard characters ('*' and '%') if
they are present in mailbox names.
7. Extension to SEARCH and SORT commands
If the server that support the NOTIFY extension also supports
CONTEXT=SEARCH and/or CONTEXT=SORT as defined in [CONTEXT], the
UPDATE return option is extended so that a client can request that
FETCH attributes be returned when a new message is added to the
context result set.
For example:
C: a00 SEARCH RETURN (COUNT UPDATE (UID BODY[HEADER.FIELDS (TO
FROM
SUBJECT)])) FROM "boss" S: * ESEARCH (TAG "a00") (COUNT
17) S: a00 OK [...a new message is delivered...] S: * EXISTS
93 S: * 93 FETCH (UID 127001 BODY[HEADER.FIELDS (FROM TO
SUBJECT)] {76} S: Subject: Re: good morning S: From:
myboss@example.org S: To: bob@example.org S: S: ) S: *
ESEARCH (TAG "a00") ADDTO (0 93)
Note that the EXISTS response MUST precede any FETCH responses, and
together they MUST precede the ESEARCH response.
No untagged FETCH response SHOULD be returned if a message becomes a
member of UPDATE SEARCH due to flag or annotation changes.
8. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation as specified in [RFC5234]. [RFC3501] defines
the non-terminals "capability", "command-auth", "mailbox", "mailbox-
data", "resp-text-code" and "search-key". The "modifier-update" non-
terminal is defined in [CONTEXT]. "mbx-list-oflag" is defined in
[RFC3501] and updated by [LISTEXT].
Except as noted otherwise, all alphabetic characters are case-
insensitive. The use of upper or lower case characters to define
token strings is for editorial clarity only. Implementations MUST
accept these strings in a case-insensitive fashion.
capability =/ "X-DRAFT-W05-NOTIFY"
;; [[Note to RFC Editor: change the capability
;; name before publication]]
King, et al. Expires September 2008 FF[Page 14]
Internet-draft March 2008
command-auth =/ notify
notify = "NOTIFY" SP
(notify-set / notify-none)
notify-set = "SET" [status-indicator] SP event-groups
; Replace registered notification events
; with the specified list of events
notify-none = "NONE"
; Cancel all registered notification
; events. The client is not interested
; in receiving any events.
status-indicator = SP "STATUS"
one-or-more-mailbox = mailbox / many-mailboxes
many-mailboxes = "(" mailbox *(SP mailbox) ")"
event-groups = event-group *(SP event-group)
event-group = "(" filter-mailboxes SP events ")"
filter-mailboxes = "selected" / "inboxes" / "personal" /
"subscribed" /
( "subtree" SP one-or-more-mailbox ) /
( "mailboxes" SP one-or-more-mailbox )
events = ( "(" event *(SP event) ")" ) / "NONE"
;; As in [MSGEVENT].
;; "NONE" means that the client does not wish
;; to receive any events for the specified
;; mailboxes.
event = message-event
/ mailbox-event / user-event / event-ext
message-match-criteria = "(" search-key ")"
message-event = ( "MessageNew" [SP
"(" fetch-att *(SP fetch-att) ")" ] )
/ "MessageExpunge"
/ "FlagChange" SP message-match-criteria
/ "AnnotationChange" SP message-match-criteria
;; "MessageNew" includes "MessageAppend" from
;; [MSGEVENT]. "FlagChange" is any of
;; "MessageRead", "MessageTrash", "FlagsSet",
King, et al. Expires September 2008 FF[Page 15]
Internet-draft March 2008
;; "FlagsClear" [MSGEVENT]. "MessageExpunge"
;; includes "MessageExpire" [MSGEVENT].
;; MessageNew and MessageExpunge MUST always
;; be specified together. If FlagChange is
;; specified, then MessageNew and MessageExpunge
;; MUST be specified as well.
;; The fett-att list may only be present for the
;; SELECTED mailbox filter (<filter-mailboxes>).
mailbox-event = "MailboxName" /
"SubscriptionChange" / "MailboxMetadataChange"
; "SubscriptionChange" includes
; MailboxSubscribe and MailboxUnSubscribe.
; "MailboxName" includes MailboxCreate,
; "MailboxDelete" and "MailboxRename".
user-event = "ServerMetadataChange"
event-ext = atom
;; For future extensions
oldname-extended-item = "OLDNAME" SP "(" mailbox ")"
;; Extended data item (mbox-list-extended-item)
;; returned in a LIST response when a mailbox is
;; renamed.
;; Note 1: the OLDNAME tag can be returned
;; with and without surrounding quotes, as per
;; mbox-list-extended-item-tag production.
resp-text-code =/ "NOTIFICATIONOVERFLOW" /
unsupported-events-code
message-event-name = "MessageNew" /
/ "MessageExpunge" / "FlagChange" /
"AnnotationChange"
event-name = message-event-name / mailbox-event /
user-event
unsupported-events-code = "BADEVENT"
SP "(" event-name *(SP event-name) ")"
modifier-update = "UPDATE"
[ "(" fetch-att *(SP fetch-att) ")" ]
mbx-list-oflag =/ "\NoAccess"
King, et al. Expires September 2008 FF[Page 16]
Internet-draft March 2008
9. Security considerations
It is very easy for a client to deny itself service using NOTIFY:
Asking for all events on all mailboxes may work on a small server,
but with a big server can swamp the client's network connection or
processing capability. In the worst case, the server's processing
could also degrade the service it offers to other clients.
Server authors should be aware that if a client issues requests and
does not listen to the resulting responses, the TCP window can
easily fill up, and a careless server might block. This problem
exists in plain IMAP, however this extension magnifies the problem.
This extensions makes it possible to retrieve messages immediately
when they are added to the mailbox. This makes it wholly impractical
to delete sensitive messages using programs like imapfilter. Using
[SIEVE] or similar is much better.
10. IANA considerations
The IANA is requested to add NOTIFY to the list of IMAP extensions,
http://www.iana.org/assignments/imap4-capabilities.
10.1. Initial LIST-EXTENDED extended data item registrations
It is requested that the following entry be added to the LIST-
EXTENDED extended data item registry [LISTEXT]:
To: iana@iana.org Subject: Registration of OLDNAME LIST-EXTENDED
extended data item
LIST-EXTENDED extended data item tag: OLDNAME
LIST-EXTENDED extended data item description: The OLDNAME extended
data item describes the old mailbox name for the mailbox identified
by the LIST response.
Which LIST-EXTENDED option(s) (and their types) causes this extended
data item to be returned (if any): none
Published specification : RFC XXXX, Section 5.4.
Security considerations: none
Intended usage: COMMON
Person and email address to contact for further information:
King, et al. Expires September 2008 FF[Page 17]
Internet-draft March 2008
Alexey Melnikov <Alexey.Melnikov@isode.com>
Owner/Change controller: iesg@ietf.org
11. Acknowedgements
The authors gratefully acknowledge the help of Peter Coates, Dave
Cridland, Mark Crispin, Cyrus Daboo, Abhijit Menon-Sen, Timo
Sirainen and Eric Burger. In particular, Peter Coates contributed
lots of text and useful suggestions to this document.
Various examples are copied from other RFCs.
This document builds on one published and two unpublished drafts by
the same authors.
12. Normative References
[RFC2119] Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March
1997.
[RFC2177] Leiba, "IMAP4 IDLE Command", RFC 2177, IBM, June 1997.
[RFC3501] Crispin, "Internet Message Access Protocol - Version
4rev1", RFC 3501, University of Washington, June 2003.
[RFC5234] Crocker, Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 5234, Brandenburg
Internetworking, THUS plc, January 2008.
[RFC4314] Melnikov, "IMAP4 Access Control List (ACL) Extension",
RFC 4314, December 2005.
[RFC4466] Melnikov, Daboo, "Collected Extensions to IMAP4 ABNF",
RFC 4466, Isode Ltd., April 2006.
[RFC4551] Melnikov, Hole, "IMAP Extension for Conditional STORE
Operation or Quick Flag Changes Resynchronization", RFC
4551, Isode Ltd., June 2006.
[LISTEXT] Leiba, Melnikov, "IMAP4 List Command Extensions", draft-
ietf-imapext-list-extensions-18 (work in progress), IBM,
September 2006.
[METADATA] Daboo, "IMAP METADATA Extension", draft-daboo-imap-
King, et al. Expires September 2008 FF[Page 18]
Internet-draft March 2008
annotatemore-12 (work in progress), Apple Computer, Inc.,
December 2007.
[MSGEVENT] Newman, C. and R. Gellens, "Internet Message Store
Events", draft-ietf-lemonade-msgevent-05.txt (work in
progress), January 2008.
[CONTEXT] Cridland, D. and C. King, "Contexts for IMAP4", work in
progress, draft-cridland-imap-context-03.txt, Isode, June
2007.
13. Informative References
[SIEVE] Guenther, P. and T. Showalter, "Sieve: A Mail Filtering
Language", RFC 5228, January 2008.
[QRESYNC] Melnikov, A., Cridland, D. and C. Wilson, "IMAP4
Extensions for Quick Mailbox Resynchronization", RFC
5162, March 2008.
[EMAIL-ARCH] Crocker, "Internet Mail Architecture", draft-crocker-
email-arch-10 (work in progress), February 2008.
14. Authors' Addresses
Curtis King
Isode Ltd
5 Castle Business Village
36 Station Road
Hampton, Middlesex TW12 2BX
UK
Email: Curtis.King@isode.com
Alexey Melnikov
Isode Ltd
5 Castle Business Village
36 Station Road
Hampton, Middlesex TW12 2BX
UK
Email: Alexey.Melnikov@isode.com
King, et al. Expires September 2008 FF[Page 19]
Internet-draft March 2008
Arnt Gulbrandsen
Oryx Mail Systems GmbH
Schweppermannstr. 8
D-81671 Muenchen
Germany
Email: arnt@oryx.com
King, et al. Expires September 2008 FF[Page 20]
Internet-draft March 2008
Intellectual Property Statement
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.
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.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
King, et al. Expires September 2008 FF[Page 21]
