Internet DRAFT - draft-melnikov-dmap
draft-melnikov-dmap
Network Working Group A. Melnikov, Ed.
Internet-Draft Isode Ltd
Intended status: Standards Track October 18, 2015
Expires: April 20, 2016
DMAP MESSAGE ACCESS PROTOCOL
draft-melnikov-dmap-00.txt
Abstract
The DMAP Message Access Protocol, Version 1 allows a client to access
and manipulate electronic mail messages on a server, without
revealing too much information about messages being accessed to the
server. DMAP permits manipulation of mailboxes (remote message
folders) in a way that is functionally equivalent to local folders.
DMAP also provides the capability for an offline client to
resynchronize with the server and for message submission. DMAP
supports discovery of keys (signets) belonging to other users the
client can communicate to. Syncronization and publication of keys
(private key, might include certificates) and signets (public part,
certificate).
DMAP includes operations for creating, deleting, and renaming
mailboxes, checking for new messages, permanently removing messages,
setting and clearing flags, RFC 5322 and RFC 2045 parsing, and
selective fetching of message attributes, texts, and portions
thereof. Messages in DMAP are accessed by the use of numbers. These
numbers are either message sequence numbers or unique identifiers.
Note: This document is a very early draft and omission of specific
syntax is intentional. It is intended to stimulate discussions about
specific protocol syntax and general design.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
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This Internet-Draft will expire on April 20, 2016.
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Table of Contents
1. How to Read This Document . . . . . . . . . . . . . . . . . . 4
1.1. Organization of This Document . . . . . . . . . . . . . . 4
1.2. Conventions Used in This Document . . . . . . . . . . . . 4
1.3. Special Notes to Implementors/To Do . . . . . . . . . . . 5
2. Design Goals . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Link Level . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Commands and Responses . . . . . . . . . . . . . . . . . 7
3.2.1. Client Protocol Sender and Server Protocol Receiver . 7
3.2.2. Server Protocol Sender and Client Protocol Receiver . 8
3.3. Message Attributes . . . . . . . . . . . . . . . . . . . 8
3.3.1. Message Numbers . . . . . . . . . . . . . . . . . . . 9
3.3.2. Flags Message Attribute . . . . . . . . . . . . . . . 11
3.3.3. Internal Date Message Attribute . . . . . . . . . . . 12
3.3.4. Size Message Attribute . . . . . . . . . . . . . . . 12
3.3.5. Body Structure Message Attribute . . . . . . . . . . 12
3.3.6. Modification Sequence (MODSEQ) Message Attribute . . 12
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3.4. Message Texts . . . . . . . . . . . . . . . . . . . . . . 13
4. State and Flow Diagram . . . . . . . . . . . . . . . . . . . 13
4.1. Not Authenticated State . . . . . . . . . . . . . . . . . 13
4.2. Authenticated State . . . . . . . . . . . . . . . . . . . 13
4.3. Selected State . . . . . . . . . . . . . . . . . . . . . 13
4.4. Logout State . . . . . . . . . . . . . . . . . . . . . . 13
5. Data Formats . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1. Atom . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.2. Number . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.3. String . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.3.1. 8-bit and Binary Strings . . . . . . . . . . . . . . 16
5.4. Parenthesized List . . . . . . . . . . . . . . . . . . . 16
5.5. NIL . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Operational Considerations . . . . . . . . . . . . . . . . . 17
6.1. Mailbox Naming . . . . . . . . . . . . . . . . . . . . . 17
6.1.1. Mailbox Hierarchy Naming . . . . . . . . . . . . . . 18
6.2. Mailbox Size and Message Status Updates . . . . . . . . . 18
6.3. Response when no Command in Progress . . . . . . . . . . 18
6.4. Autologout Timer . . . . . . . . . . . . . . . . . . . . 19
6.5. Multiple Commands in Progress (Command Pipelining) . . . 19
7. Client Commands . . . . . . . . . . . . . . . . . . . . . . . 19
7.1. Client Commands - Any State . . . . . . . . . . . . . . . 20
7.1.1. CAPABILITY Command . . . . . . . . . . . . . . . . . 20
7.1.2. NOOP Command . . . . . . . . . . . . . . . . . . . . 21
7.1.3. LOGOUT Command . . . . . . . . . . . . . . . . . . . 21
7.2. Client Commands - Not Authenticated State . . . . . . . . 21
7.2.1. AUTHENTICATE Command . . . . . . . . . . . . . . . . 22
7.3. Client Commands - Authenticated State . . . . . . . . . . 24
7.3.1. SELECT Command . . . . . . . . . . . . . . . . . . . 24
7.3.2. EXAMINE Command . . . . . . . . . . . . . . . . . . . 25
7.3.3. CREATE Command . . . . . . . . . . . . . . . . . . . 25
7.3.4. DELETE Command . . . . . . . . . . . . . . . . . . . 26
7.3.5. RENAME Command . . . . . . . . . . . . . . . . . . . 27
7.3.6. SUBSCRIBE Command . . . . . . . . . . . . . . . . . . 28
7.3.7. UNSUBSCRIBE Command . . . . . . . . . . . . . . . . . 28
7.3.8. LIST Command . . . . . . . . . . . . . . . . . . . . 29
7.3.9. STATUS Command . . . . . . . . . . . . . . . . . . . 30
7.3.10. APPEND Command . . . . . . . . . . . . . . . . . . . 31
7.4. Client Commands - Authenticated State - Key Ring
Management . . . . . . . . . . . . . . . . . . . . . . . 32
7.4.1. GETKEY Command . . . . . . . . . . . . . . . . . . . 32
7.4.2. ADDKEY Command . . . . . . . . . . . . . . . . . . . 32
7.4.3. DELETEKEY Command . . . . . . . . . . . . . . . . . . 33
7.4.4. LISTKEYS Command . . . . . . . . . . . . . . . . . . 33
7.5. Client Commands - Authenticated State - Signet Ring
Management . . . . . . . . . . . . . . . . . . . . . . . 33
7.6. Client Commands - Selected State . . . . . . . . . . . . 33
7.6.1. CLOSE Command . . . . . . . . . . . . . . . . . . . . 34
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7.6.2. EXPUNGE Command . . . . . . . . . . . . . . . . . . . 34
7.6.3. SEARCH Command . . . . . . . . . . . . . . . . . . . 35
7.6.4. FETCH Command . . . . . . . . . . . . . . . . . . . . 36
7.6.5. STORE Command . . . . . . . . . . . . . . . . . . . . 38
7.6.6. COPY Command . . . . . . . . . . . . . . . . . . . . 39
7.6.7. SUBMIT Command . . . . . . . . . . . . . . . . . . . 40
7.6.8. UID Command . . . . . . . . . . . . . . . . . . . . . 41
7.7. Client Commands - Experimental/Expansion . . . . . . . . 42
7.7.1. X<atom> Command . . . . . . . . . . . . . . . . . . . 43
8. Server Responses . . . . . . . . . . . . . . . . . . . . . . 43
8.1. Server Responses - Status Responses . . . . . . . . . . . 44
8.1.1. OK Response . . . . . . . . . . . . . . . . . . . . . 45
8.1.2. NO Response . . . . . . . . . . . . . . . . . . . . . 46
8.1.3. BAD Response . . . . . . . . . . . . . . . . . . . . 46
8.1.4. PREAUTH Response . . . . . . . . . . . . . . . . . . 46
8.1.5. BYE Response . . . . . . . . . . . . . . . . . . . . 47
8.2. Server Responses - Server and Mailbox Status . . . . . . 47
8.2.1. CAPABILITY Response . . . . . . . . . . . . . . . . . 48
8.2.2. STATUS Response . . . . . . . . . . . . . . . . . . . 48
8.2.3. FLAGS Response . . . . . . . . . . . . . . . . . . . 49
8.3. Server Responses - Mailbox Size . . . . . . . . . . . . . 49
8.3.1. EXISTS Response . . . . . . . . . . . . . . . . . . . 49
8.4. Server Responses - Message Status . . . . . . . . . . . . 49
8.4.1. FETCH Response . . . . . . . . . . . . . . . . . . . 49
8.5. Server Responses - Command Continuation Request . . . . . 51
9. Sample DMAP connection . . . . . . . . . . . . . . . . . . . 51
10. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 51
11. Security Considerations . . . . . . . . . . . . . . . . . . . 52
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52
13. Normative References . . . . . . . . . . . . . . . . . . . . 52
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 54
Appendix B. Acknowledgement . . . . . . . . . . . . . . . . . . 54
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 57
1. How to Read This Document
1.1. Organization of This Document
1.2. Conventions Used in This Document
"Conventions" are basic principles or procedures. Document
conventions are noted in this section.
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
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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 [KEYWORDS].
The word "can" (not "may") is used to refer to a possible
circumstance or situation, as opposed to an optional facility of the
protocol.
"User" is used to refer to a human user, whereas "client" refers to
the software being run by the user.
"Connection" refers to the entire sequence of client/server
interaction from the initial establishment of the network connection
until its termination.
"Session" refers to the sequence of client/server interaction from
the time that a mailbox is selected (SELECT or EXAMINE command) until
the time that selection ends (SELECT or EXAMINE of another mailbox,
CLOSE command, or connection termination).
Characters are 8-bit UTF-8 unless otherwise specified.
1.3. Special Notes to Implementors/To Do
[[CREF1: This section needs to be rewritten or removed before
publication.]]
This specification is experimental. While early implementations are
encouraged, there are lots of open issues and possibility for
drastical change to the protocol. Implementors are enouraged to
contact authors of this specification before starting implementing
this specification.
The following changes are planned (this is not an exhaustive list):
Include LITERAL+ syntax.
Incorporate IDLE
Merge LIST and STATUS into a single command
Fix the mailbox (folder) hierarchy separator character to be "."
Reorganize sections to group command by purpose.
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2. Design Goals
This protocols strives to satisfy the following goals (note that some
of the goals are in conflict, so certain compromises were made):
Any DMAP connection is always protected by TLS. [[CREF2: Add text
about server TLS identity verification.]]
Most of the message content and associated metadata is encrypted
with a key only known to DMAP clients, so DMAP servers get very
limited access to user data.
Open Issue: should the list of mailbox names be accessible to
the server (unencrypted)? What about their attributes (e.g.
mailbox roles, such as Sent or Drafts)? It might still be
possible for a server (or MITM attacker) to figure out mailbox
roles based on usage pattern.
Open Issue: should it be possible for the server to search for
messages which contain a particular message flag (in that case
such flags should be stored unencrypted)?
Open Issue: is it useful to support searching for all messages
from or to a particular domain? (Compare this with searching
for a particular sender/recipient, which is useful)
The protocol allows for efficient bandwidth usage for mobile
clients. For example, it should be possible to download a message
body structure, which is much smaller than the message itself and
allows the client to decide which body parts is worth downloading.
Also, it should be possible to download binary body parts (without
any Content Transfer Encoding).
Submission of new messages through DMAP is supported in order to
make client configuration easier.
The best bits of the IMAP protocol are reused, making
implementations slightly easier.
3. Protocol Overview
3.1. Link Level
The DMAP protocol assumes a reliable data stream such as that
provided by TCP. When TCP is used, an DMAP server listens on port
XXX.
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3.2. Commands and Responses
An DMAP connection consists of the establishment of a client/server
network connection, mandatory TLS authentication exchange . Once TLS
exchange completes successfully the connection proceeds with an
initial greeting from the server, and client/server interactions.
These client/server interactions consist of a client command, server
data, and a server completion result response.
[[CREF3: Might need revising if this changes.]]> All interactions
transmitted by client and server are in the form of lines, that is,
strings that end with a CRLF. The protocol receiver of an DMAP
client or server is either reading a line, or is reading a sequence
of octets with a known count followed by a line.
3.2.1. Client Protocol Sender and Server Protocol Receiver
The client command begins an operation. Each client command is
prefixed with an identifier (typically a short alphanumeric string,
e.g., A0001, A0002, etc.) called a "tag". A different tag is
generated by the client for each command.
Clients MUST follow the syntax outlined in this specification
strictly. It is a syntax error to send a command with missing or
extraneous spaces or arguments.
There are two cases in which a line from the client does not
represent a complete command. In one case, a command argument is
quoted with an octet count (see the description of literal in String
under Data Formats); in the other case, the command arguments require
server feedback (see the AUTHENTICATE command). In either case, the
server sends a command continuation request response if it is ready
for the octets (if appropriate) and the remainder of the command.
This response is prefixed with the token "+".
Note: If instead, the server detected an error in the command, it
sends a BAD completion response with a tag matching the command
(as described below) to reject the command and prevent the client
from sending any more of the command.
It is also possible for the server to send a completion response
for some other command (if multiple commands are in progress), or
untagged data. In either case, the command continuation request
is still pending; the client takes the appropriate action for the
response, and reads another response from the server. In all
cases, the client MUST send a complete command (including
receiving all command continuation request responses and command
continuations for the command) before initiating a new command.
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The protocol receiver of an DMAP server reads a command line from the
client, parses the command and its arguments, and transmits server
data and a server command completion result response.
3.2.2. Server Protocol Sender and Client Protocol Receiver
Data transmitted by the server to the client and status responses
that do not indicate command completion are prefixed with the token
"*", and are called untagged responses.
Server data MAY be sent as a result of a client command, or MAY be
sent unilaterally by the server. There is no syntactic difference
between server data that resulted from a specific command and server
data that were sent unilaterally.
The server completion result response indicates the success or
failure of the operation. It is tagged with the same tag as the
client command which began the operation. Thus, if more than one
command is in progress, the tag in a server completion response
identifies the command to which the response applies. There are
three possible server completion responses: OK (indicating success),
NO (indicating failure), or BAD (indicating a protocol error such as
unrecognized command or command syntax error).
Servers SHOULD enforce the syntax outlined in this specification
strictly. Any client command with a protocol syntax error, including
(but not limited to) missing or extraneous spaces or arguments,
SHOULD be rejected, and the client given a BAD server completion
response.
The protocol receiver of an DMAP client reads a response line from
the server. It then takes action on the response based upon the
first token of the response, which can be a tag, a "*", or a "+".
A client MUST be prepared to accept any server response at all times.
This includes server data that was not requested. Server data SHOULD
be recorded, so that the client can reference its recorded copy
rather than sending a command to the server to request the data. In
the case of certain server data, the data MUST be recorded.
This topic is discussed in greater detail in the Server Responses
section.
3.3. Message Attributes
In addition to message text, each message has several attributes
associated with it. These attributes can be retrieved individually
or in conjunction with other attributes or message texts.
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3.3.1. Message Numbers
TBD: decide if message sequence numbers are needed
Messages in DMAP are accessed by one of two numbers; the unique
identifier or the message sequence number.
3.3.1.1. Unique Identifier (UID) Message Attribute
An unsigned 32-bit value assigned to each message, which when used
with the unique identifier validity value (see below) forms a 64-bit
value that MUST NOT refer to any other message in the mailbox or any
subsequent mailbox with the same name forever. Unique identifiers
are assigned in a strictly ascending fashion in the mailbox; as each
message is added to the mailbox it is assigned a higher UID than the
message(s) which were added previously. Unlike message sequence
numbers, unique identifiers are not necessarily contiguous.
The unique identifier of a message MUST NOT change during the
session, and SHOULD NOT change between sessions. Any change of
unique identifiers between sessions MUST be detectable using the
UIDVALIDITY mechanism discussed below. Persistent unique identifiers
are required for a client to resynchronize its state from a previous
session with the server (e.g., disconnected or offline access
clients).
Associated with every mailbox are two 32-bit unsigned values which
aid in unique identifier handling: the next unique identifier value
(UIDNEXT) and the unique identifier validity value (UIDVALIDITY).
The next unique identifier value is the predicted value that will be
assigned to a new message in the mailbox. Unless the unique
identifier validity also changes (see below), the next unique
identifier value MUST have the following two characteristics. First,
the next unique identifier value MUST NOT change unless new messages
are added to the mailbox; and second, the next unique identifier
value MUST change whenever new messages are added to the mailbox,
even if those new messages are subsequently expunged.
Note: The next unique identifier value is intended to provide a
means for a client to determine whether any messages have been
delivered to the mailbox since the previous time it checked this
value. It is not intended to provide any guarantee that any
message will have this unique identifier. A client can only
assume, at the time that it obtains the next unique identifier
value, that messages arriving after that time will have a UID
greater than or equal to that value.
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The unique identifier validity value is sent in a UIDVALIDITY
response code in an OK untagged response at mailbox selection time.
Unique identifiers MUST persist at all times. The following
considerations about unique identifiers apply:
1. Unique identifiers MUST be strictly ascending in the mailbox
at all times. If the physical message store is re-ordered (or
messages are modified) by a non-DMAP agent, this requires that
the unique identifiers in the mailbox be regenerated, since
the former unique identifiers are no longer strictly ascending
as a result of the re-ordering.
2. If the mailbox is deleted and a new mailbox with the same name
is created at a later date (or another mailbox is renamed to
have the name of a previously deleted or renamed mailbox), the
server must either keep track of unique identifiers from the
previous instance of the mailbox, or it must assign a new
UIDVALIDITY value to the new instance of the mailbox. A good
UIDVALIDITY value to use in this case is a 32-bit
representation of the creation date/time of the mailbox. It
is alright to use a constant such as 1, but only if it
guaranteed that unique identifiers will never be reused, even
in the case of a mailbox being deleted (or renamed) and a new
mailbox by the same name created at some future time.
3. The combination of mailbox name, UIDVALIDITY, and UID must
refer to a single immutable message on that server forever.
In particular, the internal date, message size, body
structure, and message texts (all BODY[...] fetch data items)
must never change. This does not include message numbers, nor
does it include attributes that can be set by a STORE command
(e.g., FLAGS).
3.3.1.2. Message Sequence Number Message Attribute
A relative position from 1 to the number of messages in the mailbox.
This position MUST be ordered by ascending unique identifier. As
each new message is added, it is assigned a message sequence number
that is 1 higher than the number of messages in the mailbox before
that new message was added.
Message sequence numbers can be reassigned during the session. For
example, when a message is permanently removed (expunged) from the
mailbox, the message sequence number for all subsequent messages is
decremented. The number of messages in the mailbox is also
decremented. Similarly, a new message can be assigned a message
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sequence number that was once held by some other message prior to an
expunge.
In addition to accessing messages by relative position in the
mailbox, message sequence numbers can be used in mathematical
calculations. For example, if an untagged "11 EXISTS" is received,
and previously an untagged "8 EXISTS" was received, three new
messages have arrived with message sequence numbers of 9, 10, and 11.
Another example, if message 287 in a 523 message mailbox has UID
12345, there are exactly 286 messages which have lesser UIDs and 236
messages which have greater UIDs.
3.3.2. Flags Message Attribute
A list of zero or more named tokens associated with the message. A
flag is set by its addition to this list, and is cleared by its
removal. There are two types of flags in DMAP. A flag of either
type can be permanent or session-only.
A system flag is a flag name that is pre-defined in this
specification. All system flags begin with "\". Certain system
flags (\Deleted and \Seen) have special semantics described
elsewhere. The currently-defined system flags are: [[CREF4: Alexey:
some of these should be moved to the encrypted per message metadata
block.]]
\Seen Message has been read.
\Answered Message has been answered.
\Forwarded Message has been forwarded.
\Flagged Message is "flagged" for urgent/special attention.
\Deleted Message is "deleted" for removal by later EXPUNGE.
\Draft Message has not completed composition (marked as a draft).
\Submitted and \SubmitPending The \SubmitPending flag designates the
message as awaiting to be submitted. This keyword allows storing
messages waiting to be submitted in the same mailbox where
messages that were already submitted and/or are being edited are
stored. A mail client sets this flag when it decides that the
message needs to be sent out. When a client (it might be a
different client from the one that decided that the message is
pending submission) starts sending the message, it atomically adds
the \Submitted flag. Once submission is successful, the
\SubmitPending flag is atomically cleared. The two flags allow
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messages being actively submitted (messages that have both
\Submitted and \SubmitPending flags set) to be distinguished from
messages awaiting to be submitted, or from messages already
submitted. They also allow all messages that were supposed to be
submitted to be found, if the client submitting them crashes or
quits before submitting them. [[CREF5: Update SUBMIT to also talk
about these flags.]]
A keyword is defined by the server implementation. Keywords do not
begin with "\". Servers MAY permit the client to define new keywords
in the mailbox (see the description of the PERMANENTFLAGS response
code for more information). Keywords registered in documents that
extend this specification SHOULD start with "$".
A flag can be permanent or session-only on a per-flag basis.
Permanent flags are those which the client can add or remove from the
message flags permanently; that is, concurrent and subsequent
sessions will see any change in permanent flags. Changes to session
flags are valid only in that session.
3.3.3. Internal Date Message Attribute
The internal date and time of the message on the server. This is not
the date and time in the [RFC-5322] header, but rather a date and
time which reflects when the message was received. In the case of
messages delivered via DMTP , this SHOULD be the date and time of
final delivery of the message. In the case of messages delivered by
the DMAP COPY command, this SHOULD be the internal date and time of
the source message. In the case of messages delivered by the DMAP
APPEND command, this SHOULD be the date and time as specified in the
APPEND command description. All other cases are implementation
defined.
3.3.4. Size Message Attribute
The number of octets in the message.
3.3.5. Body Structure Message Attribute
A parsed representation of the body structure information of the
message.
3.3.6. Modification Sequence (MODSEQ) Message Attribute
A 63 bits positive integer that gets incremented every time there is
a change to one of mutable attributes of a message. (Currently such
mutable attributes only include message flags).
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3.4. Message Texts
In addition to being able to fetch the full text of a message, DMAP
permits the fetching of portions of the full message. Specifically,
it is possible to fetch any message chunk.
4. State and Flow Diagram
Once the connection between client and server is established, an DMAP
connection is in one of four states. The initial state is identified
in the server greeting. Most commands are only valid in certain
states. It is a protocol error for the client to attempt a command
while the connection is in an inappropriate state, and the server
will respond with a BAD or NO (depending upon server implementation)
command completion result.
4.1. Not Authenticated State
In the not authenticated state, the client MUST supply authentication
credentials before most commands will be permitted. This state is
entered when a connection starts unless the connection has been pre-
authenticated.
4.2. Authenticated State
In the authenticated state, the client is authenticated and MUST
select a mailbox to access before commands that affect messages will
be permitted. This state is entered when a pre-authenticated
connection starts, when acceptable authentication credentials have
been provided, after an error in selecting a mailbox, or after a
successful CLOSE command.
4.3. Selected State
TBD: Decide if Selected state can be eliminated entirely
In a selected state, a mailbox has been selected to access. This
state is entered when a mailbox has been successfully selected.
4.4. Logout State
In the logout state, the connection is being terminated. This state
can be entered as a result of a client request (via the LOGOUT
command) or by unilateral action on the part of either the client or
server.
If the client requests the logout state, the server MUST send an
untagged BYE response and a tagged OK response to the LOGOUT command
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before the server closes the connection; and the client MUST read the
tagged OK response to the LOGOUT command before the client closes the
connection.
A server MUST NOT unilaterally close the connection without sending
an untagged BYE response that contains the reason for having done so.
A client SHOULD NOT unilaterally close the connection, and instead
SHOULD issue a LOGOUT command. If the server detects that the client
has unilaterally closed the connection, the server MAY omit the
untagged BYE response and simply close its connection.
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+----------------------+
|connection established|
+----------------------+
||
\/
+--------------------------------------+
| server greeting |
+--------------------------------------+
|| (1) || (2) || (3)
\/ || ||
+-----------------+ || ||
|Not Authenticated| || ||
+-----------------+ || ||
|| (7) || (4) || ||
|| \/ \/ ||
|| +----------------+ ||
|| | Authenticated |<=++ ||
|| +----------------+ || ||
|| || (7) || (5) || (6) ||
|| || \/ || ||
|| || +--------+ || ||
|| || |Selected|==++ ||
|| || +--------+ ||
|| || || (7) ||
\/ \/ \/ \/
+--------------------------------------+
| Logout |
+--------------------------------------+
||
\/
+-------------------------------+
|both sides close the connection|
+-------------------------------+
(1) connection without pre-authentication (OK greeting)
(2) pre-authenticated connection (PREAUTH greeting)
(3) rejected connection (BYE greeting)
(4) successful AUTHENTICATE command
(5) successful SELECT or EXAMINE command
(6) CLOSE command, or failed SELECT or EXAMINE command
(7) LOGOUT command, server shutdown, or connection closed
5. Data Formats
DMAP uses textual commands and responses. Data in DMAP can be in one
of several forms: atom, number, string, parenthesized list, or NIL.
Note that a particular data item may take more than one form; for
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example, a data item defined as using "astring" syntax may be either
an atom or a string.
5.1. Atom
An atom consists of one or more non-special characters.
5.2. Number
A number consists of one or more digit characters, and represents a
numeric value.
5.3. String
A string is in one of two forms: either literal or quoted string.
The literal form is the general form of string. The quoted string
form is an alternative that avoids the overhead of processing a
literal at the cost of limitations of characters which may be used.
A literal is a sequence of zero or more octets (including CR and LF),
prefix-quoted with an octet count in the form of an open brace ("{"),
the number of octets, close brace ("}"), and CRLF. In the case of
literals transmitted from server to client, the CRLF is immediately
followed by the octet data. In the case of literals transmitted from
client to server, the client MUST wait to receive a command
continuation request (described later in this document) before
sending the octet data (and the remainder of the command).
A quoted string is a sequence of zero or more 7-bit characters,
excluding CR and LF, with double quote (<">) characters at each end.
The empty string is represented as either "" (a quoted string with
zero characters between double quotes) or as {0} followed by CRLF (a
literal with an octet count of 0).
Note: Even if the octet count is 0, a client transmitting a
literal MUST wait to receive a command continuation request.
5.3.1. 8-bit and Binary Strings
...Include direct support for BINARY-like literals.
5.4. Parenthesized List
Data structures are represented as a "parenthesized list"; a sequence
of data items, delimited by space, and bounded at each end by
parentheses. A parenthesized list can contain other parenthesized
lists, using multiple levels of parentheses to indicate nesting.
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The empty list is represented as () -- a parenthesized list with no
members.
5.5. NIL
The special form "NIL" represents the non-existence of a particular
data item that is represented as a string or parenthesized list, as
distinct from the empty string "" or the empty parenthesized list ().
Note: NIL is never used for any data item which takes the form of
an atom. For example, a mailbox name of "NIL" is a mailbox named
NIL as opposed to a non-existent mailbox name. This is because
mailbox uses "astring" syntax which is an atom or a string.
Conversely, an addr-name of NIL is a non-existent personal name,
because addr-name uses "nstring" syntax which is NIL or a string,
but never an atom.
6. Operational Considerations
The following rules are listed here to ensure that all DMAP
implementations interoperate properly.
6.1. Mailbox Naming
Mailbox names are encoded in UTF-8.
The case-insensitive mailbox name INBOX is a special name reserved to
mean "the primary mailbox for this user on this server". The
interpretation of all other names is implementation-dependent.
In particular, this specification takes no position on case
sensitivity in non-INBOX mailbox names. Some server implementations
are fully case-sensitive; others preserve case of a newly-created
name but otherwise are case-insensitive; and yet others coerce names
to a particular case. Client implementations MUST interact with any
of these.
There are certain client considerations when creating a new mailbox
name:
1. Any character which is one of the atom-specials (see the Formal
Syntax) will require that the mailbox name be represented as a
quoted string or literal.
2. CTL and other non-graphic characters are difficult to represent
in a user interface and are thus disallowed.
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3. Although the list-wildcard characters ("%" and "*") are valid in
a mailbox name, it is difficult to use such mailbox names with
the LIST command due to the conflict with wildcard
interpretation.
4. The "/" character is reserved to delimit levels of hierarchy.
6.1.1. Mailbox Hierarchy Naming
If it is desired to export hierarchical mailbox names, mailbox names
MUST be left-to-right hierarchical using a single "/" character to
separate levels of hierarchy.
6.2. Mailbox Size and Message Status Updates
At any time, a server can send data that the client did not request.
Sometimes, such behavior is REQUIRED. For example, agents other than
the server MAY add messages to the mailbox (e.g., new message
delivery), change the flags of the messages in the mailbox (e.g.,
simultaneous access to the same mailbox by multiple agents), or even
remove messages from the mailbox. A server MUST send mailbox size
updates automatically if a mailbox size change is observed during the
processing of a command. A server SHOULD send message flag updates
automatically, without requiring the client to request such updates
explicitly.
Special rules exist for server notification of a client about the
removal of messages to prevent synchronization errors; see the
description of the EXPUNGE response for more detail. In particular,
it is NOT permitted to send an EXISTS response that would reduce the
number of messages in the mailbox; only the EXPUNGE response can do
this.
Regardless of what implementation decisions a client makes on
remembering data from the server, a client implementation MUST record
mailbox size updates. It MUST NOT assume that any command after the
initial mailbox selection will return the size of the mailbox.
6.3. Response when no Command in Progress
Server implementations are permitted to send an untagged response
(except for EXPUNGE) while there is no command in progress. Server
implementations that send such responses MUST deal with flow control
considerations. Specifically, they MUST either (1) verify that the
size of the data does not exceed the underlying transport's available
window size, or (2) use non-blocking writes.
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6.4. Autologout Timer
If a server has an inactivity autologout timer that applies to
sessions after authentication, the duration of that timer MUST be at
least 30 minutes. The receipt of ANY command from the client during
that interval SHOULD suffice to reset the autologout timer.
6.5. Multiple Commands in Progress (Command Pipelining)
The client MAY send another command without waiting for the
completion result response of a command, subject to ambiguity rules
(see below) and flow control constraints on the underlying data
stream. Similarly, a server MAY begin processing another command
before processing the current command to completion, subject to
ambiguity rules. However, any command continuation request responses
and command continuations MUST be negotiated before any subsequent
command is initiated.
The exception is if an ambiguity would result because of a command
that would affect the results of other commands. Clients MUST NOT
send multiple commands without waiting if an ambiguity would result.
If the server detects a possible ambiguity, it MUST execute commands
to completion in the order given by the client.
7. Client Commands
DMAP commands are described in this section. Commands are organized
by the state in which the command is permitted. Commands which are
permitted in multiple states are listed in the minimum permitted
state (for example, commands valid in authenticated and selected
state are listed in the authenticated state commands).
Command arguments, identified by "Arguments:" in the command
descriptions below, are described by function, not by syntax. The
precise syntax of command arguments is described in the Formal Syntax
(Section 10).
Some commands cause specific server responses to be returned; these
are identified by "Responses:" in the command descriptions below.
See the response descriptions in the Responses section for
information on these responses, and the Formal Syntax section for the
precise syntax of these responses. It is possible for server data to
be transmitted as a result of any command. Thus, commands that do
not specifically require server data specify "no specific responses
for this command" instead of "none".
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The "Result:" in the command description refers to the possible
tagged status responses to a command, and any special interpretation
of these status responses.
The state of a connection is only changed by successful commands
which are documented as changing state. A rejected command (BAD
response) never changes the state of the connection or of the
selected mailbox. A failed command (NO response) generally does not
change the state of the connection or of the selected mailbox; the
exception being the SELECT and EXAMINE commands.
7.1. Client Commands - Any State
The following commands are valid in any state: CAPABILITY, NOOP, and
LOGOUT.
7.1.1. CAPABILITY Command
Arguments: none
Responses: REQUIRED untagged response: CAPABILITY
Result: OK - capability completed
BAD - command unknown or arguments invalid
The CAPABILITY command requests a listing of capabilities that the
server supports. The server MUST send a single untagged CAPABILITY
response with "DMAP=..." (see below) as one of the listed
capabilities before the (tagged) OK response.
The DMAP= capability describes in which mode DMAP operates. It MUST
be followed by one of "TRUSTFUL", "CAUTIOUS" or "PARANOID". [[CREF6:
Add more details about different modes and how they change the
behaviour]]
A capability name which begins with "AUTH=" indicates that the server
supports that particular authentication mechanism. All such names
are, by definition, part of this specification. For example, the
authorization capability for an experimental "blurdybloop"
authenticator would be "AUTH=XBLURDYBLOOP" and not
"XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".
Other capability names refer to extensions, revisions, or amendments
to this specification. See the documentation of the CAPABILITY
response for additional information. No capabilities, beyond the
base DMAP set defined in this specification, are enabled without
explicit client action to invoke the capability.
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See the section entitled "Client Commands - Experimental/Expansion"
for information about the form of site or implementation-specific
capabilities.
7.1.2. NOOP Command
Arguments: none
Responses: no specific responses for this command (but see below)
Result: OK - noop completed
BAD - arguments invalid
The NOOP command always succeeds. It does nothing.
Since any command can return a status update as untagged data, the
NOOP command can be used as a periodic poll for new messages or
message status updates during a period of inactivity (this is the
preferred method to do this). The NOOP command can also be used to
reset any inactivity autologout timer on the server.
7.1.3. LOGOUT Command
Arguments: none
Responses: REQUIRED untagged response: BYE
Result: OK - logout completed
BAD - command unknown or arguments invalid
The LOGOUT command informs the server that the client is done with
the connection. The server MUST send a BYE untagged response before
the (tagged) OK response, and then close the network connection.
7.2. Client Commands - Not Authenticated State
In the not authenticated state, the AUTHENTICATE command establishes
authentication and enters the authenticated state. The AUTHENTICATE
command provides a general mechanism for a variety of authentication
techniques, privacy protection, and integrity checking.
[[CREF7: Is this still a useful feature in DMAP context?]] Server
implementations MAY allow access to certain mailboxes without
establishing authentication. This can be done by means of the
ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. The
restrictions placed on anonymous users are implementation-dependent.
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Once authenticated (including as anonymous), it is not possible to
re-enter not authenticated state.
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
the following commands are valid in the not authenticated state:
AUTHENTICATE. See the Security Considerations section for important
information about these commands.
7.2.1. AUTHENTICATE Command
Arguments: authentication mechanism name
Responses: continuation data can be requested
Result: OK - authenticate completed, now in authenticated state
NO - authenticate failure: unsupported authentication
mechanism, credentials rejected
BAD - command unknown or arguments invalid,
authentication exchange cancelled
The AUTHENTICATE command indicates a [SASL] authentication mechanism
to the server. If the server supports the requested authentication
mechanism, it performs an authentication protocol exchange to
authenticate and identify the client. It MAY also negotiate an
OPTIONAL security layer for subsequent protocol interactions. If the
requested authentication mechanism is not supported, the server
SHOULD reject the AUTHENTICATE command by sending a tagged NO
response.
The AUTHENTICATE command supports the optional "initial response"
feature of [SASL].
The service name specified by this protocol's profile of [SASL] is
"DMAP".
The authentication protocol exchange consists of a series of server
challenges and client responses that are specific to the
authentication mechanism. A server challenge consists of a command
continuation request response with the "+" token followed by a BASE64
encoded string. The client response consists of a single line
consisting of a BASE64 encoded string. If the client wishes to
cancel an authentication exchange, it issues a line consisting of a
single "*". If the server receives such a response, or if it
receives an invalid BASE64 string (e.g. characters outside the
BASE64 alphabet, or non-terminal "="), it MUST reject the
AUTHENTICATE command by sending a tagged BAD response.
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If a security layer is negotiated through the [SASL] authentication
exchange, it takes effect immediately following the CRLF that
concludes the authentication exchange for the client, and the CRLF of
the tagged OK response for the server.
While client and server implementations MUST implement the
AUTHENTICATE command itself, it is not required to implement any
authentication mechanisms other than the STACIE mechanism described
in [[Add ref]]. Also, an authentication mechanism is not required to
support any security layers.
Note: a server implementation MUST implement a configuration in
which it does NOT permit any plaintext password mechanisms such as
PLAIN. Server sites SHOULD NOT use any configuration which
permits a plaintext password mechanism. Client and server
implementations SHOULD implement additional [SASL] mechanisms that
do not use plaintext passwords, such as STACIE, SCRAM [[CREF8: Add
references]], and/or the GSSAPI mechanism described in [SASL].
Servers and clients can support multiple authentication mechanisms.
The server SHOULD list its supported authentication mechanisms in the
response to the CAPABILITY command so that the client knows which
authentication mechanisms to use.
A server MAY include a CAPABILITY response code in the tagged OK
response of a successful AUTHENTICATE command in order to send
capabilities automatically. It is unnecessary for a client to send a
separate CAPABILITY command if it recognizes these automatic
capabilities. This should only be done if a security layer was not
negotiated by the AUTHENTICATE command, because the tagged OK
response as part of an AUTHENTICATE command is not protected by
encryption/integrity checking. [SASL] requires the client to re-
issue a CAPABILITY command in this case. The server MAY advertise
different capabilities after a successful AUTHENTICATE command.
If an AUTHENTICATE command fails with a NO response, the client MAY
try another authentication mechanism by issuing another AUTHENTICATE
command. In other words, the client MAY request authentication types
in decreasing order of preference.
The authorization identity passed from the client to the server
during the authentication exchange is interpreted by the server as
the user name whose privileges the client is requesting.
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7.3. Client Commands - Authenticated State
In the authenticated state, commands that manipulate mailboxes as
atomic entities are permitted. Of these commands, the SELECT and
EXAMINE commands will select a mailbox for access and enter the
selected state. [[CREF9: Should we also add "one shot resync"
commands a la QRESYNC/JMAP?]]
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
the following commands are valid in the authenticated state: SELECT,
EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST,
STATUS, and APPEND, as well as key ring and signet ring management
commands described in subsequent sections.
7.3.1. SELECT Command
Arguments: mailbox name
Responses: REQUIRED untagged responses: FLAGS, EXISTS
REQUIRED OK untagged responses: PERMANENTFLAGS,
UIDNEXT, UIDVALIDITY
Result: OK - select completed, now in selected state
NO - select failure, now in authenticated state: no
such mailbox, can't access mailbox
BAD - command unknown or arguments invalid
The SELECT command selects a mailbox so that messages in the mailbox
can be accessed. Before returning an OK to the client, the server
MUST send the following untagged data to the client.
FLAGS Defined flags in the mailbox. See the description of the
FLAGS response for more detail.
<n> EXISTS The number of messages in the mailbox. See the
description of the EXISTS response for more detail.
OK [PERMANENTFLAGS (<list of flags>)] A list of message flags that
the client can change permanently. If this is missing, the client
should assume that all flags can be changed permanently.
OK [UIDNEXT <n>] The next unique identifier value. Refer to
Section 3.3.1.1 for more information.
OK [UIDVALIDITY <n>] The unique identifier validity value. Refer to
Section 3.3.1.1 for more information. If this is missing, the
server does not support unique identifiers.
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Only one mailbox can be selected at a time in a connection;
simultaneous access to multiple mailboxes requires multiple
connections. The SELECT command automatically deselects any
currently selected mailbox before attempting the new selection.
[[CREF10: Add CLOSED response to delimit old and new mailbox state.]]
Consequently, if a mailbox is selected and a SELECT command that
fails is attempted, no mailbox is selected.
If the client is permitted to modify the mailbox, the server SHOULD
prefix the text of the tagged OK response with the "[READ-WRITE]"
response code.
If the client is not permitted to modify the mailbox but is permitted
read access, the mailbox is selected as read-only, and the server
MUST prefix the text of the tagged OK response to SELECT with the
"[READ-ONLY]" response code. Read-only access through SELECT differs
from the EXAMINE command in that certain read-only mailboxes MAY
permit the change of permanent state on a per-user (as opposed to
global) basis.
7.3.2. EXAMINE Command
Arguments: mailbox name
Responses: REQUIRED untagged responses: FLAGS, EXISTS
REQUIRED OK untagged responses: PERMANENTFLAGS,
UIDNEXT, UIDVALIDITY
Result: OK - examine completed, now in selected state
NO - examine failure, now in authenticated state: no
such mailbox, can't access mailbox BAD - command unknown
or arguments invalid
The EXAMINE command is identical to SELECT and returns the same
output; however, the selected mailbox is identified as read-only. No
changes to the permanent state of the mailbox, including per-user
state, are permitted.
The text of the tagged OK response to the EXAMINE command MUST begin
with the "[READ-ONLY]" response code.
7.3.3. CREATE Command
Arguments: mailbox name
Responses: no specific responses for this command
Result: OK - create completed
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NO - create failure: can't create mailbox with that name
BAD - command unknown or arguments invalid
The CREATE command creates a mailbox with the given name. [[CREF11:
Encrypted mailbox name?]] An OK response is returned only if a new
mailbox with that name has been created. It is an error to attempt
to create INBOX or a mailbox with a name that refers to an extant
mailbox. Any error in creation will return a tagged NO response.
If the mailbox name is suffixed with the server's hierarchy separator
character (as returned from the server by a LIST command), this is a
declaration that the client intends to create mailbox names under
this name in the hierarchy. Server implementations that do not
require this declaration MUST ignore the declaration. In any case,
the name created is without the trailing hierarchy delimiter.
If the server's hierarchy separator character appears elsewhere in
the name, the server SHOULD create any superior hierarchical names
that are needed for the CREATE command to be successfully completed.
In other words, an attempt to create "foo/bar/zap" on a server in
which "/" is the hierarchy separator character SHOULD create foo/ and
foo/bar/ if they do not already exist.
If a new mailbox is created with the same name as a mailbox which was
deleted, its unique identifiers MUST be greater than any unique
identifiers used in the previous incarnation of the mailbox UNLESS
the new incarnation has a different unique identifier validity value.
See the description of the UID command for more detail.
7.3.4. DELETE Command
Arguments: mailbox name
Responses: no specific responses for this command
Result: OK - delete completed
NO - delete failure: can't delete mailbox with that name
BAD - command unknown or arguments invalid
The DELETE command permanently removes the mailbox with the given
name. A tagged OK response is returned only if the mailbox has been
deleted. It is an error to attempt to delete INBOX or a mailbox name
that does not exist.
The DELETE command MUST NOT remove inferior hierarchical names. For
example, if a mailbox "foo" has an inferior "foo.bar" (assuming "."
is the hierarchy delimiter character), removing "foo" MUST NOT remove
"foo.bar". It is an error to attempt to delete a name that has
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inferior hierarchical names and also has the \Noselect mailbox name
attribute (see the description of the LIST response for more
details).
It is permitted to delete a name that has inferior hierarchical names
and does not have the \Noselect mailbox name attribute. If the
server implementation does not permit deleting the name while
inferior hierarchical names exists the \Noselect mailbox name
attribute is set for that name. In any case, all messages in that
mailbox are removed by the DELETE command.
The value of the highest-used unique identifier of the deleted
mailbox MUST be preserved so that a new mailbox created with the same
name will not reuse the identifiers of the former incarnation, UNLESS
the new incarnation has a different unique identifier validity value.
See the description of the UID command for more detail.
7.3.5. RENAME Command
Arguments: existing mailbox name
new mailbox name
Responses: no specific responses for this command
Result: OK - rename completed
NO - rename failure: can't rename mailbox with that name,
can't rename to mailbox with that name
BAD - command unknown or arguments invalid
The RENAME command changes the name of a mailbox. A tagged OK
response is returned only if the mailbox has been renamed. It is an
error to attempt to rename from a mailbox name that does not exist or
to a mailbox name that already exists. Any error in renaming will
return a tagged NO response.
If the name has inferior hierarchical names, then the inferior
hierarchical names MUST also be renamed. For example, a rename of
"foo" to "zap" will rename "foo/bar" (assuming "/" is the hierarchy
delimiter character) to "zap/bar".
If the server's hierarchy separator character appears in the name,
the server SHOULD create any superior hierarchical names that are
needed for the RENAME command to complete successfully. In other
words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a
server in which "/" is the hierarchy separator character SHOULD
create baz/ and baz/rag/ if they do not already exist.
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The value of the highest-used unique identifier of the old mailbox
name MUST be preserved so that a new mailbox created with the same
name will not reuse the identifiers of the former incarnation, UNLESS
the new incarnation has a different unique identifier validity value.
See the description of the UID command for more detail.
[[CREF12: If we always support returning roles for mailboxes, there
is no need for this special behaviour.]] Renaming INBOX is permitted,
and has special behavior. It moves all messages in INBOX to a new
mailbox with the given name, leaving INBOX empty. If the server
implementation supports inferior hierarchical names of INBOX, these
are unaffected by a rename of INBOX.
7.3.6. SUBSCRIBE Command
Arguments: mailbox
Responses: no specific responses for this command
Result: OK - subscribe completed
NO - subscribe failure: can't subscribe to that name
BAD - command unknown or arguments invalid
The SUBSCRIBE command adds the specified mailbox name to the server's
set of "active" or "subscribed" mailboxes as returned by the LIST
(SUBSCRIBED) command. This command returns a tagged OK response only
if the subscription is successful.
A server MAY validate the mailbox argument to SUBSCRIBE to verify
that it exists. However, it MUST NOT unilaterally remove an existing
mailbox name from the subscription list even if a mailbox by that
name no longer exists. [[CREF13: Do we need this restriction?]]
Note: This requirement is because a server site can choose to
routinely remove a mailbox with a well-known name (e.g., "system-
alerts") after its contents expire, with the intention of
recreating it when new contents are appropriate.
7.3.7. UNSUBSCRIBE Command
Arguments: mailbox name
Responses: no specific responses for this command
Result: OK - unsubscribe completed
NO - unsubscribe failure: can't unsubscribe that name
BAD - command unknown or arguments invalid
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The UNSUBSCRIBE command removes the specified mailbox name from the
server's set of "active" or "subscribed" mailboxes as returned by the
LIST (SUBSCRIBED) command. This command returns a tagged OK response
only if the unsubscription is successful. [[CREF14: We can allow
UNSUBSCRIBE to succeed for a mailbox which is not subscribed.]]
7.3.8. LIST Command
Arguments: OPTIONAL selection options
mailbox name with possible wildcards
OPTIONAL return options
Responses: untagged responses: LIST
Result: OK - list completed
NO - list failure: can't list that reference or name
BAD - command unknown or arguments invalid
[[CREF15: Update to include options, like "SUBSCRIBED".]] The LIST
command returns a subset of names from the complete set of all names
available to the client. Zero or more untagged LIST replies are
returned, containing the name attributes, hierarchy delimiter, name,
and optional mailbox status information; see the description of the
LIST reply for more detail.
The LIST command SHOULD return its data quickly, without undue delay.
If each name requires 1 second of processing, then a list of 1200
names would take 20 minutes!
The returned mailbox names MUST match the supplied mailbox name
pattern.
The character "*" is a wildcard, and matches zero or more characters
at this position. The character "%" is similar to "*", but it does
not match a hierarchy delimiter. If the "%" wildcard is the last
character of a mailbox name argument, matching levels of hierarchy
are also returned. If these levels of hierarchy are not also
selectable mailboxes, they are returned with the \Noselect mailbox
name attribute (see the description of the LIST response for more
details).
Server implementations are permitted to "hide" otherwise accessible
mailboxes from the wildcard characters, by preventing certain
characters or names from matching a wildcard in certain situations.
For example, a UNIX-based server might restrict the interpretation of
"*" so that an initial "/" character does not match.
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[[CREF16: Is this needed with roles?]] The special name INBOX is
included in the output from LIST, if INBOX is supported by this
server for this user and if the uppercase string "INBOX" matches the
mailbox name arguments with wildcards as described above. The
criteria for omitting INBOX is whether SELECT INBOX will return
failure; it is not relevant whether the user's real INBOX resides on
this or some other server.
7.3.9. STATUS Command
Arguments: mailbox name
status data item names
Responses: REQUIRED untagged responses: STATUS
Result: OK - status completed
NO - status failure: no status for that name
BAD - command unknown or arguments invalid
The STATUS command requests the status of the indicated mailbox. It
does not change the currently selected mailbox, nor does it affect
the state of any messages in the queried mailbox.
The STATUS command provides an alternative to opening a second DMAP
connection and doing an EXAMINE command on a mailbox to query that
mailbox's status without deselecting the current mailbox in the first
DMAP connection.
Unlike the LIST command, the STATUS command is not guaranteed to be
fast in its response. Under certain circumstances, it can be quite
slow. In some implementations, the server is obliged to open the
mailbox read-only internally to obtain certain status information.
Also unlike the LIST command, the STATUS command does not accept
wildcards. [[CREF17: Remove this restriction?]]
Note: The STATUS command is intended to access the status of
mailboxes other than the currently selected mailbox. Because the
STATUS command can cause the mailbox to be opened internally, and
because this information is available by other means on the
selected mailbox, the STATUS command SHOULD NOT be used on the
currently selected mailbox.
The STATUS command MUST NOT be used as a "check for new messages
in the selected mailbox" operation (refer to sections 7,
Section 8.3.1 for more information about the proper method for new
message checking).
The currently defined status data items that can be requested are:
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MESSAGES The number of messages in the mailbox.
UIDNEXT The next unique identifier value of the mailbox. Refer to
Section 3.3.1.1 for more information.
UIDVALIDITY The unique identifier validity value of the mailbox.
Refer to Section 3.3.1.1 for more information.
UNSEEN The number of messages which do not have the \Seen flag set.
7.3.10. APPEND Command
Arguments: mailbox name
OPTIONAL flag parenthesized list
OPTIONAL date/time string
message literal
Responses: no specific responses for this command
Result: OK - append completed
NO - append error: can't append to that mailbox, error
in flags or date/time or message text
BAD - command unknown or arguments invalid
The APPEND command appends the literal argument as a new message to
the end of the specified destination mailbox. This argument SHOULD
be in the format of a DMIME message. Binary data is permitted in the
message.
If a flag parenthesized list is specified, the flags SHOULD be set in
the resulting message; otherwise, the flag list of the resulting
message is set to empty by default.
If a date-time is specified, the internal date SHOULD be set in the
resulting message; otherwise, the internal date of the resulting
message is set to the current date and time by default.
If the append is unsuccessful for any reason, the mailbox MUST be
restored to its state before the APPEND attempt; no partial appending
is permitted.
If the destination mailbox does not exist, a server MUST return an
error, and MUST NOT automatically create the mailbox. Unless it is
certain that the destination mailbox can not be created, the server
MUST send the response code "[TRYCREATE]" as the prefix of the text
of the tagged NO response. This gives a hint to the client that it
can attempt a CREATE command and retry the APPEND if the CREATE is
successful.
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If the mailbox is currently selected, the normal new message actions
MUST occur. Specifically, the server MUST notify the client
immediately via an untagged EXISTS response.
Note: The APPEND command is not used for message submission.
7.4. Client Commands - Authenticated State - Key Ring Management
This section describes user's key ring management commands: GETKEY,
ADDKEY, DELETEKEY, LISTKEYS.
7.4.1. GETKEY Command
Arguments: key ID
key part indicator (PRIVATE, PUBLIC or BOTH)
Responses: REQUIRED untagged responses: KEY
Result: OK - getkey completed
NO - getkey failure: the key with key id was not found
BAD - arguments invalid
The GETKEY command requests the server to return private key, public
key or both.
7.4.2. ADDKEY Command
Arguments: key ID
Signet Signing Request (might contain public key or both
public and private key)
Responses: none
Result: OK - addkey completed
NO - addkey failure: the key already exists or storage
failure
BAD - arguments invalid
The ADDKEY command requests the server to add the specified public
key or both public key and the corresponding private key to the key
ring. [[CREF18: Whether both or just public key are uploaded depends
on the DMAP mode.]]
It is an error to add a key with the key id which already exists.
[[CREF19: Add more details about the response code to be returned in
such case.]] DELETEKEY should be used first to delete such key.
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7.4.3. DELETEKEY Command
Arguments: key ID
Responses: none
Result: OK - deletekey completed
NO - deletekey failure: the key is not found
BAD - arguments invalid
The DELETEKEY command requests the server to delete the corresponding
public (and the associated private, if exists) key using the key
identifier.
DELETEKEY MUST fail with a tagged NO response if there are any
messages on the server associated with the key id or if the expiry of
the key hasn't been reached.
7.4.4. LISTKEYS Command
Arguments: None
Responses: KEY untagged response for each key
Result: OK - listkeys completed
NO - listkeys failure: no status for that name
BAD - arguments invalid
The LISTKEYS command requests the server to return key ids of all
keys in the key ring. Each key id is returned using the KEY untagged
response which doesn't include anything other than the key id.
7.5. Client Commands - Authenticated State - Signet Ring Management
This section describes signet ring management commands: GETSIGNET,
ADDSIGNET, DELETESIGNET, LISTSIGNETS.
[[CREF20: TBD. Email address is used instead of key id to
get/add/delete/list. LISTSIGNETS should allow for wildcards.]]
7.6. Client Commands - Selected State
In the selected state, commands that manipulate messages in a mailbox
are permitted.
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
and the authenticated state commands (SELECT, EXAMINE, CREATE,
DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, STATUS and APPEND), the
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following commands are valid in the selected state: CLOSE, EXPUNGE,
SEARCH , FETCH, STORE, COPY, SUBMIT and UID.
7.6.1. CLOSE Command
Arguments: none
Responses: no specific responses for this command
Result: OK - close completed, now in authenticated state
BAD - command unknown or arguments invalid
The CLOSE command permanently removes all messages that have the
\Deleted flag set from the currently selected mailbox, and returns to
the authenticated state from the selected state. No untagged EXPUNGE
responses are sent.
No messages are removed, and no error is given, if the mailbox is
selected by an EXAMINE command or is otherwise selected read-only.
Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT command
MAY be issued without previously issuing a CLOSE command. The
SELECT, EXAMINE, and LOGOUT commands implicitly close the currently
selected mailbox without doing an expunge. However, when many
messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT sequence is
considerably faster than an EXPUNGE-LOGOUT or EXPUNGE-SELECT because
no untagged EXPUNGE responses (which the client would probably
ignore) are sent.
7.6.2. EXPUNGE Command
Arguments: none
Responses: untagged responses: EXPUNGE
Result: OK - expunge completed
NO - expunge failure: can't expunge (e.g., permission
denied)
BAD - command unknown or arguments invalid
[[CREF21: Switch to returning UIDs in EXPUNGE response?]] The EXPUNGE
command permanently removes all messages that have the \Deleted flag
set from the currently selected mailbox. Before returning an OK to
the client, an untagged EXPUNGE response is sent for each message
that is removed. Note that if any messages with the \Recent flag set
are expunged, an untagged RECENT response is sent after the untagged
EXPUNGE(s) to update the client's count of RECENT messages.
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7.6.3. SEARCH Command
Arguments: searching criteria (one or more)
Responses: REQUIRED untagged response: SEARCH
Result: OK - search completed
NO - search error: can't search that criteria
BAD - command unknown or arguments invalid
The SEARCH command searches the mailbox for messages that match the
given searching criteria. Searching criteria consist of one or more
search keys. The untagged SEARCH response from the server contains a
listing of message sequence numbers corresponding to those messages
that match the searching criteria.
When multiple keys are specified, the result is the intersection (AND
function) of all the messages that match those keys. For example,
the criteria DELETED SINCE 1-Feb-2015 refers to all deleted messages
that were placed in the mailbox since February 1, 2015. A search key
can also be a parenthesized list of one or more search keys (e.g.,
for use with the OR and NOT keys).
In all search keys that use strings, a message matches the key if the
string is a substring of the associated text. The matching is case-
insensitive. Note that the empty string is a substring.
The defined search keys are as follows. Refer to the Formal Syntax
section for the precise syntactic definitions of the arguments.
<sequence set> Messages with message sequence numbers corresponding
to the specified message sequence number set.
ALL All messages in the mailbox; the default initial key for ANDing.
BEFORE <date> Messages whose internal date (disregarding time and
timezone) is earlier than the specified date.
DELETED Messages with the \Deleted flag set.
LARGER <n> Messages with an [RFC-5322] size larger than the
specified number of octets.
NOT <search-key> Messages that do not match the specified search
key.
ON <date> Messages whose internal date (disregarding time and
timezone) is within the specified date.
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OR <search-key1> <search-key2> Messages that match either search
key.
SEEN Messages that have the \Seen flag set.
SINCE <date> Messages whose internal date (disregarding time and
timezone) is within or later than the specified date.
SMALLER <n> Messages with an [RFC-5322] size smaller than the
specified number of octets.
UID <sequence set> Messages with unique identifiers corresponding to
the specified unique identifier set. Sequence set ranges are
permitted.
UNDELETED Messages that do not have the \Deleted flag set.
UNSEEN Messages that do not have the \Seen flag set.
7.6.4. FETCH Command
Arguments: sequence set
message data item names or macro
Responses: untagged responses: FETCH
Result: OK - fetch completed
NO - fetch error: can't fetch that data
BAD - command unknown or arguments invalid
The FETCH command retrieves data associated with a message in the
mailbox. The data items to be fetched can be either a single atom or
a parenthesized list.
[[CREF22: Make sure the following statement is true once ABNF is
done.]] Most data items, identified in the formal syntax under the
msg-att-static rule, are static and MUST NOT change for any
particular message. Other data items, identified in the formal
syntax under the msg-att-dynamic rule, MAY change, either as a result
of a STORE command or due to external events.
For example, if a client receives a BODYSTRUCTURE for a message
when it already knows the envelope, it can safely ignore the newly
transmitted body structure.
There are three macros which specify commonly-used sets of data
items, and can be used instead of data items. A macro must be used
by itself, and not in conjunction with other macros or data items.
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FAST Macro equivalent to: (FLAGS INTERNALDATE SIZE)
FULL Macro equivalent to: (FLAGS INTERNALDATE SIZE BODYSTRUCTURE)
The currently defined data items that can be fetched are:
BODY[<section>]<<partial>>
The content of a particular chunk or of the whole message. The
section specification has the following syntax: <chunk-
type>.<chunk-number>. For example "0.1" - the first Tracing
chunk. "67.2" - the second Display-Content chunk. [[CREF23:
This needs more thought. In particular, is nesting of body
parts allowed?]]
The section specification can be the empty string, in which
case the content of the whole message is returned.
It is possible to fetch a substring of the designated text.
This is done by appending an open angle bracket ("<"), the
octet position of the first desired octet, a period, the
maximum number of octets desired, and a close angle bracket
(">") to the part specifier. If the starting octet is beyond
the end of the text, an empty string is returned.
Any partial fetch that attempts to read beyond the end of the
text is truncated as appropriate. A partial fetch that starts
at octet 0 is returned as a partial fetch, even if this
truncation happened.
Note: This means that BODY[]<0.2048> of a 1500-octet message
will return BODY[]<0> with a literal of size 1500, not
BODY[].
The \Seen flag is implicitly set; if this causes the flags to
change, they SHOULD be included as part of the FETCH responses.
BODY.PEEK[<section>]<<partial>> An alternate form of BODY[<section>]
that does not implicitly set the \Seen flag.
BODYSTRUCTURE
[[CREF24: Decide if this is going to be binary or human
readable (e.g. a list).]]
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The BODYSTRUCTURE FETCH item contains basic information about
all chunks of the message which enables clients to download
only specific chunks of the message without downloading the
whole message. This is computed by the server by extracting
available chunk types and associated data from the message.
This can provide performance improvements when dealing with big
attachments.
FLAGS The flags that are set for this message.
META Encrypted block of data that represents mutable state
associated with the message, such as encrypted flags. [[CREF25:
TBD]]
MODSEQ The message modification sequence. It is a 63 bit unsigned
integer (expressed as a decimal), which changes every time
message's flags or encrypted metadata block changes. [[CREF26:
TBD]]
INTERNALDATE The internal date of the message.
SIZE The size of the message in octets.
UID The unique identifier for the message.
7.6.5. STORE Command
Arguments: sequence set
message data item name
value for message data item
Responses: untagged responses: FETCH
Result: OK - store completed
NO - store error: can't store that data
BAD - command unknown or arguments invalid
The STORE command alters data associated with a message in the
mailbox. Normally, STORE will return the updated value of the data
with an untagged FETCH response. A suffix of ".SILENT" in the data
item name prevents the untagged FETCH, and the server SHOULD assume
that the client has determined the updated value itself or does not
care about the updated value.
Note: Regardless of whether or not the ".SILENT" suffix was used,
the server SHOULD send an untagged FETCH response if a change to a
message's flags from an external source is observed. The intent
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is that the status of the flags is determinate without a race
condition.
The currently defined data items that can be stored are:
FLAGS <flag list> Replace the flags for the message (other than
\Recent) with the argument. The new value of the flags is
returned as if a FETCH of those flags was done.
FLAGS.SILENT <flag list> Equivalent to FLAGS, but without returning
a new value.
+FLAGS <flag list> Add the argument to the flags for the message.
The new value of the flags is returned as if a FETCH of those
flags was done.
+FLAGS.SILENT <flag list> Equivalent to +FLAGS, but without
returning a new value.
-FLAGS <flag list> Remove the argument from the flags for the
message. The new value of the flags is returned as if a FETCH of
those flags was done.
-FLAGS.SILENT <flag list> Equivalent to -FLAGS, but without
returning a new value.
Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
S: * 2 FETCH (FLAGS (\Deleted \Seen))
S: * 3 FETCH (FLAGS (\Deleted))
S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen))
S: A003 OK STORE completed
7.6.6. COPY Command
Arguments: sequence set
mailbox name
Responses: no specific responses for this command
Result: OK - copy completed
NO - copy error: can't copy those messages or to that
name
BAD - command unknown or arguments invalid
The COPY command copies the specified message(s) to the end of the
specified destination mailbox. The flags and internal date of the
message(s) SHOULD be preserved, and the Recent flag SHOULD be set, in
the copy.
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If the destination mailbox does not exist, a server SHOULD return an
error. It SHOULD NOT automatically create the mailbox. Unless it is
certain that the destination mailbox can not be created, the server
MUST send the response code "[TRYCREATE]" as the prefix of the text
of the tagged NO response. This gives a hint to the client that it
can attempt a CREATE command and retry the COPY if the CREATE is
successful.
If the COPY command is unsuccessful for any reason, server
implementations MUST restore the destination mailbox to its state
before the COPY attempt.
Example: C: A003 COPY 2:4 MEETING
S: A003 OK COPY completed
7.6.7. SUBMIT Command
Arguments: message number of the message to send
OPTIONAL list of delivery options (e.g. "delay submission
until", etc.)
Responses: FETCH response with updated message flags
Result: OK - Message submitted for delivery
NO - Submission error: can't move to the Sent mailbox,
error
in flags or date/time or message text
BAD - arguments invalid
The SUBMIT command submits the specified message using DMTP protocol.
The server ensures that the current user key is used with the message
being submitted, so the server MUST reject messages which don't
contain a valid signature using the current signing key. The server
MUST also ensure that the origin chunk provides the correct author
information (which may be distinct from the "From" header embedded in
the meta chunk). [[CREF27: Add DMIME reference here.]] The server
also sets/clears some message flags in the process in order to
prevent other DMAP clients from submitting the same message at the
same time. This is described in more details below.
[[CREF28: One of the delivery options can specify whether to move the
submitted message to the Sent mailbox. TBD.]]
Clients MUST NOT submit a message which is either not marked with the
\SubmitPending keyword , or which is marked with the \Submitted
keyword. Servers MUST reject such a command with a tagged NO bearing
the SUBMISSIONRACE response code.
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In the course of submission, servers MUST atomically add the
\Submitted flag to the message. A transient state where the message
is temporarily marked with both \Submitted and \SubmitPending flags
MAY be hidden from any IMAP session or it MAY be visible in some or
all of them.
If the command succeeded, the message MUST be marked with the
\Submitted flag, the \SubmitPending flag MUST be cleared and a FETCH
response containing the message UID and its new flags MUST be sent.
If the command fails, the server MUST clear both the \Submitted or
\SubmitPending flags.
Clients MUST be prepared to handle failing submission at any time.
Servers MAY reject message submission for any reason.
[[CREF29: Delivery options: TBD.]] The server MUST process all
specified delivery options and their detailed options. The server
MUST respond with a tagged BAD if the client used unrecognized or
unannounced option, or if a recognized option is used in an invalid
way. If the server cannot honor a recognized and announced option,
it MUST respond with a tagged NO with the POLICYDENIED response code
and the message MUST NOT be submitted, nor its flags changed.
7.6.8. UID Command
Arguments: command name
command arguments
Responses: untagged responses: FETCH, SEARCH
Result: OK - UID command completed
NO - UID command error
BAD - command unknown or arguments invalid
The UID command has two forms. In the first form, it takes as its
arguments a COPY, FETCH, or STORE command with arguments appropriate
for the associated command. However, the numbers in the sequence set
argument are unique identifiers instead of message sequence numbers.
Sequence set ranges are permitted, but there is no guarantee that
unique identifiers will be contiguous.
A non-existent unique identifier is ignored without any error message
generated. Thus, it is possible for a UID FETCH command to return an
OK without any data or a UID COPY or UID STORE to return an OK
without performing any operations.
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In the second form, the UID command takes a SEARCH command with
SEARCH command arguments. The interpretation of the arguments is the
same as with SEARCH; however, the numbers returned in a SEARCH
response for a UID SEARCH command are unique identifiers instead of
message sequence numbers. For example, the command UID SEARCH 1:100
UID 443:557 returns the unique identifiers corresponding to the
intersection of two sequence sets, the message sequence number range
1:100 and the UID range 443:557.
Note: in the above example, the UID range 443:557 appears. The
same comment about a non-existent unique identifier being ignored
without any error message also applies here. Hence, even if
neither UID 443 or 557 exist, this range is valid and would
include an existing UID 495.
Also note that a UID range of 559:* always includes the UID of the
last message in the mailbox, even if 559 is higher than any
assigned UID value. This is because the contents of a range are
independent of the order of the range endpoints. Thus, any UID
range with * as one of the endpoints indicates at least one
message (the message with the highest numbered UID), unless the
mailbox is empty.
The number after the "*" in an untagged FETCH response is always a
message sequence number, not a unique identifier, even for a UID
command response. However, server implementations MUST implicitly
include the UID message data item as part of any FETCH response
caused by a UID command, regardless of whether a UID was specified as
a message data item to the FETCH.
Note: The rule about including the UID message data item as part of a
FETCH response primarily applies to the UID FETCH and UID STORE
commands, including a UID FETCH command that does not include UID as
a message data item. Although it is unlikely that the other UID
commands will cause an untagged FETCH, this rule applies to these
commands as well.
Example: C: A999 UID FETCH 4827313:4828442 FLAGS
S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
S: A999 OK UID FETCH completed
7.7. Client Commands - Experimental/Expansion
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7.7.1. X<atom> Command
Arguments: implementation defined
Responses: implementation defined
Result: OK - command completed
NO - failure
BAD - command unknown or arguments invalid
Any command prefixed with an X is an experimental command. Commands
which are not part of this specification, a standard or standards-
track revision of this specification, or an IESG-approved
experimental protocol, MUST use the X prefix.
Any added untagged responses issued by an experimental command MUST
also be prefixed with an X. Server implementations MUST NOT send any
such untagged responses, unless the client requested it by issuing
the associated experimental command.
Example: C: a441 CAPABILITY
S: * CAPABILITY DMAP XPIG-LATIN
S: a441 OK CAPABILITY completed
C: A442 XPIG-LATIN
S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
S: A442 OK XPIG-LATIN ompleted-cay
8. Server Responses
Server responses are in three forms: status responses, server data,
and command continuation request. The information contained in a
server response, identified by "Contents:" in the response
descriptions below, is described by function, not by syntax. The
precise syntax of server responses is described in the Formal Syntax
section.
The client MUST be prepared to accept any response at all times.
Status responses can be tagged or untagged. Tagged status responses
indicate the completion result (OK, NO, or BAD status) of a client
command, and have a tag matching the command.
Some status responses, and all server data, are untagged. An
untagged response is indicated by the token "*" instead of a tag.
Untagged status responses indicate server greeting, or server status
that does not indicate the completion of a command (for example, an
impending system shutdown alert). For historical reasons, untagged
server data responses are also called "unsolicited data", although
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strictly speaking, only unilateral server data is truly
"unsolicited".
Certain server data MUST be recorded by the client when it is
received; this is noted in the description of that data. Such data
conveys critical information which affects the interpretation of all
subsequent commands and responses (e.g., updates reflecting the
creation or destruction of messages).
Other server data SHOULD be recorded for later reference; if the
client does not need to record the data, or if recording the data has
no obvious purpose (e.g., a SEARCH response when no SEARCH command is
in progress), the data SHOULD be ignored.
An example of unilateral untagged server data occurs when the DMAP
connection is in the selected state. In the selected state, the
server checks the mailbox for new messages as part of command
execution. Normally, this is part of the execution of every command;
hence, a NOOP command suffices to check for new messages. If new
messages are found, the server sends untagged EXISTS and RECENT
responses reflecting the new size of the mailbox. Server
implementations that offer multiple simultaneous access to the same
mailbox SHOULD also send appropriate unilateral untagged FETCH and
EXPUNGE responses if another agent changes the state of any message
flags or expunges any messages.
Command continuation request responses use the token "+" instead of a
tag. These responses are sent by the server to indicate acceptance
of an incomplete client command and readiness for the remainder of
the command.
8.1. Server Responses - Status Responses
Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD
can be tagged or untagged. PREAUTH and BYE are always untagged.
Status responses MAY include an OPTIONAL "response code". A response
code consists of data inside square brackets in the form of an atom,
possibly followed by a space and arguments. The response code
contains additional information or status codes for client software
beyond the OK/NO/BAD condition, and are defined when there is a
specific action that a client can take based upon the additional
information.
The currently defined response codes are:
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ALERT The human-readable text contains a special alert that MUST be
presented to the user in a fashion that calls the user's attention
to the message.
CAPABILITY Followed by a list of capabilities. This can appear in
the initial OK or PREAUTH response to transmit an initial
capabilities list. This makes it unnecessary for a client to send
a separate CAPABILITY command if it recognizes this response.
PERMANENTFLAGS Followed by a parenthesized list of flags, indicates
which of the known flags the client can change permanently. Any
flags that are in the FLAGS untagged response, but not the
PERMANENTFLAGS list, can not be set permanently. If the client
attempts to STORE a flag that is not in the PERMANENTFLAGS list,
the server will either ignore the change or store the state change
for the remainder of the current session only. The PERMANENTFLAGS
list can also include the special flag \*, which indicates that it
is possible to create new keywords by attempting to store those
flags in the mailbox.
READ-ONLY The mailbox is selected read-only, or its access while
selected has changed from read-write to read-only.
READ-WRITE The mailbox is selected read-write, or its access while
selected has changed from read-only to read-write.
TRYCREATE An APPEND or COPY attempt is failing because the target
mailbox does not exist (as opposed to some other reason). This is
a hint to the client that the operation can succeed if the mailbox
is first created by the CREATE command.
UIDNEXT Followed by a decimal number, indicates the next unique
identifier value. Refer to Section 3.3.1.1 for more information.
UIDVALIDITY Followed by a decimal number, indicates the unique
identifier validity value. Refer to Section 3.3.1.1 for more
information.
Additional response codes defined by particular client or server
implementations SHOULD be prefixed with an "X" until they are added
to a revision of this protocol. Client implementations SHOULD ignore
response codes that they do not recognize.
8.1.1. OK Response
Contents: OPTIONAL response code
human-readable text
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The OK response indicates an information message from the server.
When tagged, it indicates successful completion of the associated
command. The human-readable text MAY be presented to the user as an
information message. The untagged form indicates an information-only
message; the nature of the information MAY be indicated by a response
code.
The untagged form is also used as one of three possible greetings at
connection startup. It indicates that the connection is not yet
authenticated and that an AUTHENTICATE command is needed.
Example: S: * OK DMAP server ready
[...]
C: A001 SELECT mailbox
[...]
S: * OK [ALERT] System shutdown in 10 minutes
S: A001 OK SELECT Completed
8.1.2. NO Response
Contents: OPTIONAL response code
human-readable text
The NO response indicates an operational error message from the
server. When tagged, it indicates unsuccessful completion of the
associated command. The untagged form indicates a warning; the
command can still complete successfully. The human-readable text
describes the condition.
8.1.3. BAD Response
Contents: OPTIONAL response code
human-readable text
The BAD response indicates an error message from the server. When
tagged, it reports a protocol-level error in the client's command;
the tag indicates the command that caused the error. The untagged
form indicates a protocol-level error for which the associated
command can not be determined; it can also indicate an internal
server failure. The human-readable text describes the condition.
8.1.4. PREAUTH Response
Contents: OPTIONAL response code
human-readable text
The PREAUTH response is always untagged, and is one of three possible
greetings at connection startup. It indicates that the connection
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has already been authenticated by external means; thus no
AUTHENTICATE command is needed.
Example: S: * PREAUTH DMAP server logged in as Smith
8.1.5. BYE Response
Contents: OPTIONAL response code
human-readable text
The BYE response is always untagged, and indicates that the server is
about to close the connection. The human-readable text MAY be
displayed to the user in a status report by the client. The BYE
response is sent under one of four conditions:
1. as part of a normal logout sequence. The server will close the
connection after sending the tagged OK response to the LOGOUT
command.
2. as a panic shutdown announcement. The server closes the
connection immediately.
3. as an announcement of an inactivity autologout. The server
closes the connection immediately.
4. as one of three possible greetings at connection startup,
indicating that the server is not willing to accept a connection
from this client. The server closes the connection immediately.
The difference between a BYE that occurs as part of a normal LOGOUT
sequence (the first case) and a BYE that occurs because of a failure
(the other three cases) is that the connection closes immediately in
the failure case. In all cases the client SHOULD continue to read
response data from the server until the connection is closed; this
will ensure that any pending untagged or completion responses are
read and processed.
Example: S: * BYE Autologout; idle for too long
8.2. Server Responses - Server and Mailbox Status
These responses are always untagged. This is how server and mailbox
status data are transmitted from the server to the client. Many of
these responses typically result from a command with the same name.
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8.2.1. CAPABILITY Response
Contents: capability listing
The CAPABILITY response occurs as a result of a CAPABILITY command.
The capability listing contains a space-separated listing of
capability names that the server supports.
The capability listing MUST include the atom "DMAP=...", which
describes in which mode DMAP operates. It MUST be followed by one of
"TRUSTFUL", "CAUTIOUS" or "PARANOID".
A capability name which begins with "AUTH=" indicates that the server
supports that particular authentication mechanism.
Other capability names indicate that the server supports an
extension, revision, or amendment to the DMAP protocol. Server
responses MUST conform to this document until the client issues a
command that uses the associated capability.
Capability names MUST either begin with "X" or be standard or
standards-track DMAP extensions, revisions, or amendments registered
with IANA. A server MUST NOT offer unregistered or non-standard
capability names, unless such names are prefixed with an "X".
Client implementations SHOULD NOT require any capability name other
than "DMAP", and MUST ignore any unknown capability names.
A server MAY send capabilities automatically, by using the CAPABILITY
response code in the initial PREAUTH or OK responses, and by sending
an updated CAPABILITY response code in the tagged OK response as part
of a successful authentication. It is unnecessary for a client to
send a separate CAPABILITY command if it recognizes these automatic
capabilities.
Example: S: * CAPABILITY DMAP AUTH=GSSAPI XPIG-LATIN
8.2.2. STATUS Response
Contents: encrypted mailbox name
status parenthesized list
The STATUS response occurs as a result of an STATUS command. It
returns the mailbox name that matches the STATUS specification and
the requested mailbox status information.
Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
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8.2.3. FLAGS Response
Contents: flag parenthesized list
The FLAGS response occurs as a result of a SELECT or EXAMINE command.
The flag parenthesized list identifies the flags (at a minimum, the
system-defined flags) that are applicable for this mailbox. Flags
other than the system flags can also exist, depending on server
implementation.
The update from the FLAGS response MUST be recorded by the client.
Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
8.3. Server Responses - Mailbox Size
These responses are always untagged. This is how changes in the size
of the mailbox are transmitted from the server to the client.
Immediately following the "*" token is a number that represents a
message count.
8.3.1. EXISTS Response
Contents: none
The EXISTS response reports the number of messages in the mailbox.
This response occurs as a result of a SELECT or EXAMINE command, and
if the size of the mailbox changes (e.g., new messages).
The update from the EXISTS response MUST be recorded by the client.
Example: S: * 23 EXISTS
8.4. Server Responses - Message Status
[[CREF30: Get rid of message numbers altogether?]] These responses
are always untagged. This is how message data are transmitted from
the server to the client, often as a result of a command with the
same name. Immediately following the "*" token is a number that
represents a message sequence number.
8.4.1. FETCH Response
Contents: message data
The FETCH response returns data about a message to the client. The
data are pairs of data item names and their values in parentheses.
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This response occurs as the result of a FETCH or STORE command, as
well as by unilateral server decision (e.g., flag updates).
The current data items are:
BODY[<section>]<<origin octet>>
A string expressing the contents of the specified chunk or of
the whole message. The section string has the following
syntax: <chunk-type>.<number>. For example "0.1" - the first
Tracing chunk. "67.2" - the second Display-Content chunk.
[[CREF31: This needs more thought.]]
The section specification can be the empty string, in which
case the content of the whole message is returned.
If the origin octet is specified, this string is a substring of
the entire body contents, starting at that origin octet. This
means that BODY[]<0> MAY be truncated, but BODY[] is NEVER
truncated.
Note: The origin octet facility MUST NOT be used by a server
in a FETCH response unless the client specifically requested
it by means of a FETCH of a BODY[<section>]<<partial>> data
item.
Binary data is allowed in responses.
BODYSTRUCTURE
[[CREF32: Decide if this is going to be binary or human
readable (e.g. a list).]]
The BODYSTRUCTURE FETCH item contains basic information about
all chunks of the message which enables clients to download
only specific chunks of the message without downloading the
whole message. This can provide performance improvements when
dealing with big attachments.
For each chunk of the message, the BODYSTRUCTURE includes (in
the following order):
chunk type One octet (for binary representation).
body size A number giving the size of the chunk in octets (3
octets in network byte order for binary representation).
FLAGS A parenthesized list of flags that are set for this message.
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META Encrypted block of data that represents mutable state
associated with the message, such as encrypted flags. [[CREF33:
TBD]]
MODSEQ A 63 bit unsigned integer (expressed as a decimal), which
represents the message modification sequence. [[CREF34: TBD]]
INTERNALDATE A string representing the internal date of the message
(delivery date or date specified in the APPEND that created the
message).
SIZE A number expressing the size of the message in octets.
UID A number expressing the unique identifier of the message.
Example: S: * 23 FETCH (FLAGS (\Seen) SIZE 44827)
8.5. Server Responses - Command Continuation Request
The command continuation request response is indicated by a "+" token
instead of a tag. This form of response indicates that the server is
ready to accept the continuation of a command from the client. The
remainder of this response is a line of text.
This response is used in the AUTHENTICATE command to transmit server
data to the client, and request additional client data. This
response is also used if an argument to any command is a literal.
[[CREF35: Add non sync literals?]] The client is not permitted to
send the octets of the literal unless the server indicates that it is
expected. This permits the server to process commands and reject
errors on a line-by-line basis. The remainder of the command,
including the CRLF that terminates a command, follows the octets of
the literal. If there are any additional command arguments, the
literal octets are followed by a space and those arguments.
9. Sample DMAP connection
The following is a transcript of an DMAP connection. A long line in
this sample is broken for editorial clarity.
TBD
10. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation as specified in [ABNF].
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In the case of alternative or optional rules in which a later rule
overlaps an earlier rule, the rule which is listed earlier MUST take
priority. For example, "\Seen" when parsed as a flag is the \Seen
flag name and not a flag-extension, even though "\Seen" can be parsed
as a flag-extension. Some, but not all, instances of this rule are
noted below.
Note: [ABNF] rules MUST be followed strictly; in particular:
(1) 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.
(2) In all cases, SP refers to exactly one space. It is NOT
permitted to substitute TAB, insert additional spaces, or
otherwise treat SP as being equivalent to LWSP.
(3) The ASCII NUL character, %x00, MUST NOT be used at any time.
TBD
11. Security Considerations
12. IANA Considerations
IMAP4 capabilities are registered by publishing a standards track or
IESG approved experimental RFC. The registry is currently located
at: http://www.iana.org/assignments/dmap-capabilities
13. Normative References
[ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[ANONYMOUS]
Zeilenga, K., "Anonymous Simple Authentication and
Security Layer (SASL) Mechanism", RFC 4505, June 2006,
<http://www.rfc-editor.org/info/rfc4505>.
[CHARSET] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, October 2000,
<http://www.rfc-editor.org/info/rfc2978>.
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[DIGEST-MD5]
Leach, P. and C. Newman, "Using Digest Authentication as a
SASL Mechanism", RFC 2831, May 2000,
<http://www.rfc-editor.org/info/rfc2831>.
[DISPOSITION]
Troost, R., Dorner, S., and K. Moore, Ed., "Communicating
Presentation Information in Internet Messages: The
Content-Disposition Header Field", RFC 2183, August 1997,
<http://www.rfc-editor.org/info/rfc2183>.
[PLAIN] Zeilenga, K., Ed., "The PLAIN Simple Authentication and
Security Layer (SASL) Mechanism", RFC 4616, August 2006,
<http://www.rfc-editor.org/info/rfc4616>.
[KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[LANGUAGE-TAGS]
Alvestrand, H., "Content Language Headers", RFC 3282, May
2002, <http://www.rfc-editor.org/info/rfc3282>.
[LOCATION]
Palme, J., Hopmann, A., and N. Shelness, "MIME
Encapsulation of Aggregate Documents, such as HTML
(MHTML)", RFC 2557, March 1999,
<http://www.rfc-editor.org/info/rfc2557>.
[MD5] Myers, J. and M. Rose, "The Content-MD5 Header Field",
RFC 1864, October 1995,
<http://www.rfc-editor.org/info/rfc1864>.
[MIME-HDRS]
Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996,
<http://www.rfc-editor.org/info/rfc2047>.
[MIME-IMB]
Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996,
<http://www.rfc-editor.org/info/rfc2045>.
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[MIME-IMT]
Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996, <http://www.rfc-editor.org/info/rfc2046>.
[RFC-5322]
Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008, <http://www.rfc-editor.org/info/rfc5322>.
[SASL] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
Authentication and Security Layer (SASL)", RFC 4422, June
2006, <http://www.rfc-editor.org/info/rfc4422>.
[TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
Appendix A. Change Log
1. TBD
Appendix B. Acknowledgement
This protocol was born after discussions with Ladar Levison. However
he might not necessarily agree with its content and all errors belong
to the editor of this document.
This document is heavily influenced by IMAP (RFC 3501) by Mark
Crispin.
This document borrows some text from draft-kundrat-imap-submit-02.txt
Index
+
+FLAGS <flag list> 39
+FLAGS.SILENT <flag list> 39
-
-FLAGS <flag list> 39
-FLAGS.SILENT <flag list> 39
A
ADDKEY (command) 32
ALERT (response code) 45
ALL (search key) 35
APPEND (command) 31
AUTHENTICATE (command) 22
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B
BAD (response) 46
BODY.PEEK[<section>]<<partial>> (fetch item) 37
BODYSTRUCTURE (fetch item) 37
BODYSTRUCTURE (fetch result) 50
BODY[<section>]<<origin octet>> (fetch result) 50
BODY[<section>]<<partial>> (fetch item) 37
BYE (response) 47
Body Structure (message attribute) 12
C
CAPABILITY (command) 20
CAPABILITY (response code) 45
CAPABILITY (response) 48
CLOSE (command) 34
COPY (command) 39
CREATE (command) 25
D
DELETE (command) 26
DELETED (search key) 35
DELETEKEY (command) 33
E
EXAMINE (command) 25
EXPUNGE (command) 34
F
FAST (fetch item) 37
FETCH (command) 36
FETCH (response) 49
FLAGS (fetch item) 38
FLAGS (fetch result) 50
FLAGS (response) 49
FLAGS <flag list> (store command data item) 39
FLAGS.SILENT <flag list> (store command data item) 39
FULL (fetch item) 37
Flags (message attribute) 11
G
GETKEY (command) 32
I
INTERNALDATE (fetch item) 38
INTERNALDATE (fetch result) 51
Internal Date (message attribute) 12
K
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Keyword (type of flag) 12
L
LARGER <n> (search key) 35
LIST (command) 29
LISTKEYS (command) 33
LOGOUT (command) 21
M
MAY (specification requirement term) 5
MESSAGES (status item) 31
META (fetch result) 38, 51
MODSEQ (fetch result) 38, 51
MUST (specification requirement term) 5
MUST NOT (specification requirement term) 5
Message Sequence Number (message attribute) 10
Modification Sequence (message attribute) 12
N
NO (response) 46
NOOP (command) 21
NOT <search-key> (search key) 35
O
OK (response) 45
ON <date> (search key) 35
OPTIONAL (specification requirement term) 5
OR <search-key1> <search-key2> (search key) 36
P
PERMANENTFLAGS (response code) 45
PREAUTH (response) 46
Permanent Flag (class of flag) 12
R
READ-ONLY (response code) 45
READ-WRITE (response code) 45
RECOMMENDED (specification requirement term) 5
RENAME (command) 27
REQUIRED (specification requirement term) 5
S
SEARCH (command) 35
SEEN (search key) 36
SELECT (command) 24
SHOULD (specification requirement term) 5
SHOULD NOT (specification requirement term) 5
SINCE <date> (search key) 36
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SIZE (fetch item) 38
SIZE (fetch result) 51
SMALLER <n> (search key) 36
STATUS (command) 30
STATUS (response) 48
STORE (command) 38
SUBMIT (command) 40
SUBSCRIBE (command) 28
Session Flag (class of flag) 12
Size (message attribute) 12
System Flag (type of flag) 11
T
TRYCREATE (response code) 45
U
UID (command) 41
UID (fetch item) 38
UID (fetch result) 51
UID <sequence set> (search key) 36
UIDNEXT (response code) 45
UIDNEXT (status item) 31
UIDVALIDITY (response code) 45
UIDVALIDITY (status item) 31
UNDELETED (search key) 36
UNSEEN (search key) 36
UNSEEN (status item) 31
UNSUBSCRIBE (command) 28
Unique Identifier (UID) (message attribute) 9
X
X<atom> (command) 43
\
\Answered (system flag) 11
\Deleted (system flag) 11
\Draft (system flag) 11
\Flagged (system flag) 11
\Forwarded (system flag) 11
\Seen (system flag) 11
\Submitted and \SubmitPending (system flags) 11
Author's Address
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Alexey Melnikov (editor)
Isode Ltd
14 Castle Mews
Hampton, Middlesex TW12 2NP
UK
Email: Alexey.Melnikov@isode.com
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