Network Working Group M. Crispin
Internet Draft: IMAP4 University of Washington
Document: internet-drafts/draft-ietf-imap-imap4-03.txt June 1994
INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4
Status of this Memo
This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas,
and its Working Groups. Note that other groups may also distribute
working documents as Internet Drafts.
Internet Drafts are draft documents valid for a maximum of six
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To learn the current status of any Internet-Draft, please check the
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munnari.oz.au.
This is a draft document of the IETF IMAP Working Group. A revised
version of this draft document will be submitted to the RFC editor as
a Proposed Standard for the Internet Community. Discussion and
suggestions for improvement are requested, and should be sent to
imap@CAC.Washington.EDU. This document will expire before 31
November 1994. Distribution of this draft is unlimited.
Abstract
The Internet Message Access Protocol, Version 4 (IMAP4) allows a
client to access and manipulate electronic mail messages on a server.
IMAP4 permits manipulation of remote message folders, called
"mailboxes", in a way that is functionally equivalent to local
mailboxes. IMAP4 also provides the capability for an offline client
to resynchronize with the server.
IMAP4 includes operations for creating, deleting, and renaming
mailboxes; checking for new messages; permanently removing messages;
setting and clearing flags; RFC 822 and MIME parsing; searching; and
selective fetching of message attributes, texts, and portions
thereof. Messages in IMAP4 are accessed by a set of either sequence
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numbers (relative position from 1 to the number of messages in the
mailbox) or immutable unique identifiers.
IMAP4 does not specify a means of posting mail; this function is
handled by a mail transfer protocol such as SMTP (RFC 821).
IMAP4 is designed to be upwards compatible from the IMAP2 protocol
described in RFC 1176.
Conventions Used in this Document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
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Table of Contents
Status of this Memo ............................................... i
Abstract .......................................................... i
Conventions Used in this Document ................................. ii
IMAP4 Protocol Specification ...................................... 1
1. Protocol Overview ......................................... 1
2. State and Flow Diagram .................................... 2
2.1. Non-Authenticated State ................................... 2
2.2. Authenticated State ....................................... 2
2.3. Selected State ............................................ 2
2.4. Logout State .............................................. 2
3. Data Formats .............................................. 4
3.1. Atom, String, Number, NIL ................................. 4
3.2. Parenthesized List ........................................ 4
3.3. 8-bit Data ................................................ 4
3.4. Binary Data ............................................... 4
4. Operational Considerations ................................ 5
4.1. Mailbox Size and Message Status Updates ................... 5
4.2. Response when no Command in Progress ...................... 5
4.3. Autologout Timer .......................................... 5
5. Client Commands ........................................... 6
5.1. Client Commands - Any State ............................... 6
5.1.1. CAPABILITY Command ........................................ 6
5.1.2. NOOP Command .............................................. 6
5.1.3. LOGOUT Command ............................................ 7
5.2. Client Commands - Non-Authenticated State ................. 7
5.2.1. AUTHENTICATE Command ...................................... 8
5.2.2. LOGIN Command ............................................. 9
5.3. Client Commands - Authenticated State ..................... 9
5.3.1. SELECT Command ............................................ 10
5.3.2. EXAMINE Command ........................................... 11
5.3.3. CREATE Command ............................................ 12
5.3.4. DELETE Command ............................................ 12
5.3.5. RENAME Command ............................................ 13
5.3.6. SUBSCRIBE Command ......................................... 14
5.3.7. UNSUBSCRIBE Command ....................................... 14
5.3.8. LIST Command .............................................. 14
5.3.9. LSUB Command .............................................. 16
5.3.10. FIND ALL.MAILBOXES Command ................................ 16
5.3.11. FIND MAILBOXES Command .................................... 17
5.3.12. APPEND Command ............................................ 18
5.4. Client Commands - Selected State .......................... 19
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5.4.1. CHECK Command ............................................. 19
5.4.2. CLOSE Command ............................................. 20
5.4.3. EXPUNGE Command ........................................... 20
5.4.4. SEARCH Command ............................................ 21
5.4.5. FETCH Command ............................................. 25
5.4.6. PARTIAL Command ........................................... 28
5.4.7. STORE Command ............................................. 29
5.4.8. COPY Command .............................................. 30
5.4.9. UID Command ............................................... 31
5.5. Client Commands - Experimental/Expansion .................. 32
5.5.1. X<atom> Command ........................................... 32
6. Server Responses .......................................... 33
6.1. Server Responses - Status Responses ....................... 33
6.1.1. OK Response ............................................... 34
6.1.2. NO Response ............................................... 35
6.1.3. BAD Response .............................................. 35
6.1.4. PREAUTH Response .......................................... 36
6.1.5. BYE Response .............................................. 36
6.2. Server Responses - Server and Mailbox Status .............. 36
6.2.1. CAPABILITY Response ....................................... 37
6.2.2. LIST Response ............................................. 37
6.2.3. LSUB Response ............................................. 38
6.2.4. MAILBOX Response .......................................... 38
6.2.5. SEARCH Response ........................................... 39
6.2.6. FLAGS Response ............................................ 39
6.3. Server Responses - Message Status ......................... 39
6.3.1. EXISTS Response ........................................... 40
6.3.2. RECENT Response ........................................... 40
6.3.3. EXPUNGE Response .......................................... 40
6.3.4. FETCH Response ............................................ 40
6.3.5. COPY Response ............................................. 45
6.3.6. STORE Response ............................................ 45
6.4. Server Responses - Command Continuation Request ........... 46
7. Sample IMAP4 session ...................................... 47
8. Formal Syntax ............................................. 48
Appendices ........................................................ 58
A. Author's Note ............................................. 58
B. Security Considerations ................................... 58
C. Author's Address .......................................... 58
D. IMAP4 Keyword Index ....................................... 59
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IMAP4 Protocol Specification
1. Protocol Overview
The IMAP4 protocol assumes a reliable data stream such as provided by
TCP. When TCP is used, an IMAP4 server listens on port 143.
An IMAP4 session consists of the establishment of a client/server
connection, 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.
The client command begins an operation and the server completion
result response indicates the success or failure of the operation.
Each client command is prefixed with a 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. This tag
is repeated as the prefix of the server completion result response,
and identifies the command to which the response applies.
Server responses that are not related to the completion of a command
are untagged. This includes data transmitted by the server to the
client, and is discussed in greater detail in the Server Responses
section.
The client is not required to wait for the completion result response
of a command before sending another command, subject to flow control
constraints on the underlying data stream. Similarly, a server is
not required to process a command to completion before beginning
processing of the next command, unless an ambiguity would result
because of a command that would affect the results of other commands.
If there is such an ambiguity, the server executes commands to
completion in the order given by the client.
Command and response arguments are described by function. The
precise syntax of command and response arguments is described in the
Formal Syntax section.
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2. State and Flow Diagram
An IMAP4 server is in one of four states:
2.1. Non-Authenticated State
In non-authenticated state, the user 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.
2.2. Authenticated State
In authenticated state, the user 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, or after an error in selecting a mailbox.
2.3. Selected State
In selected state, a mailbox has been selected to access. This state
is entered when a mailbox has been successfully selected.
2.4. Logout State
In logout state, the session is being terminated, and the server will
close the connection. This state can be entered as a result of a
client request or by unilateral server decision.
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+--------------------------------------+
|initial connection and server greeting|
+--------------------------------------+
|| (1) || (2) || (3)
VV || ||
+-----------------+ || ||
|non-authenticated| || ||
+-----------------+ || ||
|| (7) || (4) || ||
|| VV VV ||
|| +----------------+ ||
|| | authenticated |<=++ ||
|| +----------------+ || ||
|| || (7) || (5) || (6) ||
|| || VV || ||
|| || +--------+ || ||
|| || |selected|==++ ||
|| || +--------+ ||
|| || || (7) ||
VV VV VV VV
+--------------------------------------+
| logout and close connection |
+--------------------------------------+
(1) connection without pre-authentication (OK greeting)
(2) pre-authenticated connection (PREAUTH greeting)
(3) rejected connection (BYE greeting)
(4) successful LOGIN or 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
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3. Data Formats
IMAP4 uses textual commands and responses.
3.1. Atom, String, Number, NIL
Individual data items in IMAP4 are represented as atoms (one or more
non-special characters), strings (a quoted sequence of characters),
or numbers. Some data items may be either atoms or strings. The
atom "NIL" represents the non-existence of a data item, as distinct
from the empty string "" or the empty list ().
3.2. 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 may itself contain other
parenthesized lists, using multiple levels of parentheses to indicate
nesting. This is similar to the S-expression syntax of the Lisp
programming language.
3.3. 8-bit Data
8-bit textual and binary mail is supported through the use of MIME
encoding. IMAP4 implementations MAY transmit 8-bit or multi-octet
characters in literals, but should do so only when the character set
is identified.
3.4. Binary Data
Although a BINARY body encoding is defined, unencoded binary strings
are not permitted. A "binary string" is any string with NUL
characters. Implementations MUST encode binary data into a textual
form such as BASE64 before transmitting the data. A string with an
excessive amount of CTL characters may also be considered to be
binary, although this is not required.
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4. Operational Considerations
4.1. 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. 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.
Regardless of what implementation decisions a client may take on
remembering data from the server, a client implementation MUST record
mailbox size updates. It MUST NOT assume that any command after
initial mailbox selection will return the size of the mailbox.
4.2. 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.
4.3. Autologout Timer
If a server has an inactivity autologout timer, that timer MUST be of
at least 30 minutes' duration. The receipt of ANY command from the
client during that interval should suffice to reset the autologout
timer.
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5. Client Commands
5.1. Client Commands - Any State
The following commands are valid in any state: CAPABILITY, NOOP, and
LOGOUT.
5.1.1. CAPABILITY Command
Arguments: none
Data: mandatory 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 "IMAP4" as the first listed capability
before the (tagged) OK response.
Example: C: abcd CAPABILITY
S: * CAPABILITY IMAP4
S: abcd OK CAPABILITY completed
5.1.2. NOOP Command
Arguments: none
Data: no specific data for this command (but see below)
Result: OK - noop completed
BAD - command unknown or 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. The NOOP
command can also be used to reset any inactivity autologout timer
on the server.
Example: C: a002 NOOP
S: a002 OK NOOP completed
. . .
C: a047 NOOP
S: * 22 EXPUNGE
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S: * 23 EXISTS
S: * 3 RECENT
S: * 14 FETCH (FLAGS (\Seen \Deleted))
S: a047 OK NOOP completed
5.1.3. LOGOUT Command
Arguments: none
Data: mandatory 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 session. The server must send a BYE untagged response before
the (tagged) OK response, and then close the network connection.
Example: C: A023 LOGOUT
S: * BYE IMAP4 Server logging out
S: A023 OK LOGOUT completed
(Server and client then close the connection)
5.2. Client Commands - Non-Authenticated State
In non-authenticated state, the AUTHENTICATE or LOGIN command
establishes authentication and enter authenticated state. The
AUTHENTICATE command provides a general mechanism for a variety of
authentication techniques, whereas the LOGIN command uses the
traditional user name and plaintext password pair.
Server implementations may allow non-authenticated access to certain
mailboxes. The convention is to use a LOGIN command with the userid
"anonymous". A password is required. It is implementation-dependent
what requirements, if any, are placed on the password and what access
restrictions are placed on anonymous users.
Once authenticated (including as anonymous), it is not possible to
re-enter non-authenticated state.
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
the following commands are valid in non-authenticated state:
AUTHENTICATE and LOGIN.
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5.2.1. AUTHENTICATE Command
Arguments: authentication mechanism name
Data: continuation data may 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 an authentication mechanism to
the server. If the server supports the requested authentication
mechanism, it performs an authentication protocol exchange to
authenticate and identify the user. Optionally, it also
negotiates a protection mechanism 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 authentication protocol exchange consists of a series of
server challenges and client answers 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 answer consists of a line
consisting of a BASE64 encoded string. If the client wishes to
cancel an authentication exchange, it should issue a line with a
single "*". If the server receives such an answer, it must reject
the AUTHENTICATE command by sending a tagged BAD response.
A protection mechanism provides integrity and privacy protection
to the protocol session. If a protection mechanism is negotiated,
it is applied to all subsequent data sent over the connection.
The protection mechanism 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. Once the
protection mechanism is in effect, the stream of command and
response octets is processed into buffers of ciphertext. Each
buffer is transferred over the connection as a stream of octets
prepended with a four octet field in network byte order that
represents the length of the following data. The maximum
ciphertext buffer length is defined by the protection mechanism.
The server is not required to support any particular
authentication mechanism, nor are authentication mechanisms
required to support any protection mechanisms. If an AUTHENTICATE
command fails with a NO response, the client may try another
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authentication mechanism by issuing another AUTHENTICATE command,
or may attempt to authenticate by using the LOGIN command. In
other words, the client may request authentication types in
decreasing order of preference, with the LOGIN command as a last
resort.
Example: S: * OK KerberosV4 IMAP4 Server
C: A001 AUTHENTICATE KERBEROS_V4
S: + AmFYig==
C: BAcAQU5EUkVXLkNNVS5FRFUAOCAsho84kLN3/IJmrMG+25a4DT
+nZImJjnTNHJUtxAA+o0KPKfHEcAFs9a3CL5Oebe/ydHJUwYFd
WwuQ1MWiy6IesKvjL5rL9WjXUb9MwT9bpObYLGOKi1Qh
S: + or//EoAADZI=
C: DiAF5A4gA+oOIALuBkAAmw==
S: A001 OK Kerberos V4 authentication successful
Note: the line breaks in the first client answer are for
editorial clarity and are not in real authenticators.
5.2.2. LOGIN Command
Arguments: user name
password
Data: no specific data for this command
Result: OK - login completed, now in authenticated state
NO - login failure: user name or password rejected
BAD - command unknown or arguments invalid
The LOGIN command identifies the user to the server and carries
the plaintext password authenticating this user.
Example: C: a001 LOGIN SMITH SESAME
S: a001 OK LOGIN completed
5.3. Client Commands - Authenticated State
In 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 selected state.
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
the following commands are valid in authenticated state: SELECT,
EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
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FIND ALL.MAILBOXES, FIND MAILBOXES, and APPEND.
5.3.1. SELECT Command
Arguments: mailbox name
Data: mandatory untagged responses: FLAGS, EXISTS, RECENT
optional OK untagged responses: UNSEEN, PERMANENTFLAGS
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
<n> EXISTS The number of messages in the mailbox
<n> RECENT The number of messages added to the mailbox since
the previous time this mailbox was read
to define the initial state of the mailbox at the client. If it
is not possible to determine the messages that were added since
the previous time a mailbox was read, then all messages SHOULD be
considered recent.
The server SHOULD also send an UNSEEN special information token in
an OK untagged response, indicating the sequence number of the
first unseen message in the mailbox.
If the client can not change the permanent state of one or more of
the flags listed in the FLAGS untagged response, the server SHOULD
send a PERMANENTFLAGS special information token in an OK untagged
response, listing the flags that the client may change
permanently.
Only one mailbox may be selected at a time in a session;
simultaneous access to multiple mailboxes requires multiple
sessions. The SELECT command automatically deselects any
currently selected mailbox before attempting the new selection.
Consequently, if a mailbox is selected and a SELECT command that
fails is attempted, no mailbox is selected.
If the user is permitted to modify the mailbox, the server SHOULD
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prefix the text of the OK response with the "[READ-WRITE]" special
information token.
If the user 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 OK response to SELECT with
the "[READ-ONLY]" special information token. 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. Netnews messages marked in
a user's .newsrc file are an example of such per-user permanent
state that can be modified with read-only mailboxes.
Example: C: A142 SELECT INBOX
S: * 172 EXISTS
S: * 1 RECENT
S: * OK [UNSEEN 12] Message 12 is first unseen
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
S: A142 OK [READ-WRITE] SELECT completed
5.3.2. EXAMINE Command
Arguments: mailbox name
Data: mandatory untagged responses: FLAGS, EXISTS, RECENT
optional OK untagged responses: UNSEEN, PERMANENTFLAGS
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 an OK response to the EXAMINE command MUST begin with
the "[READ-ONLY]" special information token.
Example: C: A932 EXAMINE blurdybloop
S: * 17 EXISTS
S: * 2 RECENT
S: * OK [UNSEEN 8] Message 8 is first unseen
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
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S: A932 OK [READ-ONLY] EXAMINE completed
5.3.3. CREATE Command
Arguments: mailbox name
Data: no specific data for this command
Result: OK - create completed
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. 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 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 may, in the
future, create mailbox names under this name in the hierarchy.
Server implementations that do not require this declaration MUST
ignore it.
Example: C: A003 CREATE owatagusiam/
S: A003 OK CREATE completed
C: A004 CREATE owatagusiam/blurdybloop
S: A004 OK CREATE completed
Note: the interpretation of this example depends on whether
"/" was returned as the hierarchy separator from LIST. If
"/" is the hierarchy separator, a new level of hierarchy
named "owatagusiam" with a member called "blurdybloop" is
created. Otherwise, two mailboxes at the same hierarchy
level are created.
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5.3.4. DELETE Command
Arguments: mailbox name
Data: no specific data 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. An 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. Any error in deletion will return a NO
response.
Example: C: A683 DELETE blurdybloop
S: A683 OK DELETE completed
5.3.5. RENAME Command
Arguments: existing mailbox name
new mailbox name
Data: no specific data 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. An 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 NO response.
Renaming INBOX is permitted; a new, empty INBOX is created in its
place.
Example: C: Z4S9 RENAME blurdybloop owatagusiam
S: Z4S9 OK RENAME completed
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5.3.6. SUBSCRIBE Command
Arguments: mailbox
Data: no specific data 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 list of "active" or "subscribed" mailboxes as returned by
the LSUB command. This command returns an OK response only if the
subscription is successful.
The optional word "MAILBOX" may appear after "SUBSCRIBE". It has
no effect on the execution of the command.
Example: C: A002 SUBSCRIBE #news.comp.mail.mime
S: A002 OK SUBSCRIBE completed
5.3.7. UNSUBSCRIBE Command
Arguments: mailbox name
Data: no specific data for this command
Result: OK - unsubscribe completed
NO - unsubscribe failure: can't unsubscribe that name
BAD - command unknown or arguments invalid
The UNSUBSCRIBE command removes the specified mailbox name from
the server's list of "active" or "subscribed" mailboxes as
returned by the LSUB command. This command returns an OK response
only if the unsubscription is successful.
The optional word "MAILBOX" may appear after "UNSUBSCRIBE". It
has no effect on the execution of the command.
Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime
S: A002 OK UNSUBSCRIBE completed
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5.3.8. LIST Command
Arguments: reference name
mailbox name with possible wildcards
Data: untagged responses: LIST
Result: OK - list completed
NO - list failure: can't list that reference or name
BAD - command unknown or arguments invalid
The LIST command returns a subset of names from the complete set
of all names available to the user. Zero or more untagged LIST
replies are returned, containing the name attributes, hierarchy
delimiter, and name; see the description of the LIST reply for
more detail.
An empty ("" string) reference argument indicates that the mailbox
name is interpreted as by SELECT. The returned mailbox names MUST
match the supplied mailbox name pattern. A non-empty reference
argument is the name of a mailbox or a level of mailbox hierarchy,
and indicates a context in which the mailbox name is interpreted
in an implementation-defined manner.
The reference and mailbox name arguments are canonicalized to an
interpreted form that represents an unambiguous left-to-right
hierarchy. The returned mailbox names will be in the interpreted
form. Any part of the reference that is included in the
interpreted form SHOULD be in the same form as the reference
argument and not canonicalized into some other form.
Here are some examples of how references and mailbox
names might be interpreted on a UNIX-based server:
Reference Mailbox Name Interpretation
------------ ------------ --------------
~smith/Mail/ foo.* ~smith/Mail/foo.*
~smith/Mail/ /usr/doc/foo /usr/doc/foo
archive/ % archive/%
archive/ ~fred/Mail/* ~fred/Mail/*
#news. comp.mail.* #news.comp.mail.*
Note that "~smith/Mail" should not be canonicalized into
something like "/u2/users/smith/Mail" because
"~smith/Mail" is taken from the reference and thus its
form should be preserved.
The character "*" is a wildcard, and matches zero or more
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characters at this position. The character "%" is similar to "*",
but it does not match a hierarchy delimiter.
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.
The special name INBOX is included in the output from LIST if it
matches the input arguments and INBOX is supported by this server
for this user. 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.
Example: C: A002 LIST "~/Mail/" "%"
S: * LIST (\Noselect) "/" ~/Mail/foo
S: * LIST () "/" ~/Mail/meetings
S: A002 OK LIST completed
5.3.9. LSUB Command
Arguments: reference name
mailbox name with possible wildcards
Data: untagged responses: LSUB
Result: OK - lsub completed
NO - lsub failure: can't list that reference or name
BAD - command unknown or arguments invalid
The LSUB command returns a subset of names from the set of names
that the user has declared as being "active" or "subscribed".
Zero or more untagged LSUB replies are returned. The arguments to
LSUB are in the same form as those for LIST.
Example: C: A002 LSUB "#news." "comp.mail.*"
S: * LSUB () "." #news.comp.mail.mime
S: * LSUB () "." #news.comp.mail.misc
S: A002 OK LSUB completed
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5.3.10. FIND ALL.MAILBOXES Command
Arguments: mailbox name with possible wildcards
Data: untagged responses: MAILBOX
Result: OK - find completed
NO - find failure: can't list that name
BAD - command unknown or arguments invalid
This command is OBSOLETE. It is NOT required to support it in new
server implementations. It is documented here for the benefit of
implementors who may wish to support it for compatibility with old
client implementations.
The FIND ALL.MAILBOXES command returns a subset of names from the
complete set of all names available to the user. It returns zero
or more untagged MAILBOX replies. The mailbox argument to FIND
ALL.MAILBOXES is similar to that for LIST with an empty reference,
except that the characters "%" and "?" match a single character.
Example: C: A002 FIND ALL.MAILBOXES *
S: * MAILBOX blurdybloop
S: * MAILBOX INBOX
S: A002 OK FIND ALL.MAILBOXES completed
5.3.11. FIND MAILBOXES Command
Arguments: mailbox name with possible wildcards
Data: untagged responses: MAILBOX
Result: OK - find completed
NO - find failure: can't list that name
BAD - command unknown or arguments invalid
This command is OBSOLETE. It is NOT required to support it in new
server implementations. It is documented here for the benefit of
implementors who may wish to support it for compatibility with old
client implementations.
The FIND MAILBOXES command returns a subset of names from the set
of names that the user has declared as being "active" or
"subscribed". It returns zero or more untagged MAILBOX replies.
The mailbox argument to FIND MAILBOXES is similar to that for LSUB
with an empty reference, except that the characters "%" and "?"
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match a single character.
Example: C: A002 FIND MAILBOXES *
S: * MAILBOX blurdybloop
S: * MAILBOX INBOX
S: A002 OK FIND MAILBOXES completed
5.3.12. APPEND Command
Arguments: mailbox name
optional flag list
optional date/time string
message literal
Data: no specific data 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
in the specified destination mailbox. This argument is in the
format of an RFC 822 message. 8-bit characters are permitted in
the message. A server implementation that is unable to preserve
8-bit data properly MUST be able to reversibly convert 8-bit
APPEND data to 7-bit using MIME.
If a flag list or date_time are specified, that data SHOULD be set
in the resulting message; otherwise, the defaults of empty flags
and the current date/time are used.
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 mailbox is currently selected, the
normal new mail actions should occur.
Server implementations SHOULD return a NO response if the length
of the literal is zero.
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 special information token "[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
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the APPEND if the CREATE is successful.
Example: C: A003 APPEND saved-messages (\Seen) {310}
C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
C: From: Fred Foobar <foobar@Blurdybloop.COM>
C: Subject: afternoon meeting
C: To: mooch@owatagu.siam.edu
C: Message-Id: <B27397-0100000@Blurdybloop.COM>
C: Mime-Version: 1.0
C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
C:
C: Hello Joe, do you think we can meet at 3:30 tomorrow?
C:
S: A003 OK APPEND completed
Note: the APPEND command is not used for message delivery,
because it does not provide a mechanism to transfer SMTP
(RFC 821) envelope information.
5.4. Client Commands - Selected State
In 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, LSUB, FIND
ALL.MAILBOXES, FIND MAILBOXES, and APPEND), the following commands
are valid in the selected state: CHECK, CLOSE, EXPUNGE, SEARCH,
FETCH, PARTIAL, STORE, COPY, and UID.
5.4.1. CHECK Command
Arguments: none
Data: no specific data for this command
Result: OK - check completed
BAD - command unknown or arguments invalid
The CHECK command requests a checkpoint of the currently selected
mailbox. A checkpoint refers to any implementation-dependent
housekeeping associated with the mailbox (e.g. resolving the
server's in-memory state of the mailbox with the state on its
disk) that is not normally executed as part of each command. A
checkpoint may take a non-instantaneous amount of real time to
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complete. If a server implementation has no such housekeeping
considerations, CHECK is equivalent to NOOP.
There is no guarantee that an EXISTS untagged response will happen
as a result of CHECK. NOOP, not CHECK, should be used for new
mail polling.
Example: C: FXXZ CHECK
S: FXXZ OK CHECK Completed
5.4.2. CLOSE Command
Arguments: none
Data: no specific data for this command
Result: OK - close completed, now in authenticated state
NO - close failure: no mailbox selected
BAD - command unknown or arguments invalid
The CLOSE command permanently removes from the currently selected
mailbox all messages that have the \Deleted flag set, and returns
to authenticated state from 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 when a mailbox is selected, it is not required to send a
CLOSE command before a SELECT, EXAMINE, or LOGOUT 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.
Example: C: A341 CLOSE
S: A341 OK CLOSE completed
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5.4.3. EXPUNGE Command
Arguments: none
Data: untagged responses: EXPUNGE
Result: OK - expunge completed
NO - expunge failure: can't expunge (e.g. permission
denied)
BAD - command unknown or arguments invalid
The EXPUNGE command permanently removes from the currently
selected mailbox all messages that have the \Deleted flag set.
Before returning an OK to the client, an untagged EXPUNGE response
is sent for each message that is removed. The message number for
each successive message in the mailbox is immediately decremented
by 1; and this decrement is reflected in subsequent untagged
EXPUNGE responses.
Example: C: A202 EXPUNGE
S: * 3 EXPUNGE
S: * 3 EXPUNGE
S: * 5 EXPUNGE
S: * 8 EXPUNGE
S: A202 OK EXPUNGE completed
Note: in this example, messages 3, 4, 7, and 11 had the
\Deleted flag set.
5.4.4. SEARCH Command
Arguments: optional character set specification
searching criteria (one or more)
Data: mandatory untagged response: SEARCH
Result: OK - search completed
NO - search error: can't search that character set or
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 numbers corresponding to those
messages that match the searching criteria.
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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 FROM "SMITH" SINCE 1-Feb-1994 refers
to all deleted messages from Smith that were placed in the mailbox
since February 1, 1994. A search key may also be a parenthesized
list of one or more search keys (e.g. for use with the OR and NOT
keys).
Server implementations MAY exclude MIME body parts with terminal
content types other than TEXT and MESSAGE from consideration in
SEARCH matching.
The optional character set specification consists of the word
CHARSET followed by a registered MIME character set. It indicates
the character set of the strings that appear in the search
criteria. RFC 1522 strings that appear in RFC 822/MIME message
headers, and MIME content transfer encodings, MUST be decoded
before matching. Except for US-ASCII, it is not required that any
particular character set be supported. If the server does not
support the specified character set, it MUST return a tagged NO
response (not a BAD).
In all search keys that use strings, a message matches the key if
the string is a substring of the field. The matching is case-
insensitive.
The currently defined search keys are as follows. Refer to the
Formal Syntax section for the precise syntactic definitions of the
arguments.
<sequence> Messages within the specified sequence range.
ALL All messages in the mailbox; the default initial
key for ANDing.
ANSWERED Messages with the \Answered flag set.
BCC <string> Messages that contain the specified string in the
envelope structure's BCC field.
BEFORE <date> Messages whose internal date is earlier than the
specified date.
BODY <string> Messages that contain the specified string in the
body of the message.
CC <string> Messages that contain the specified string in the
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envelope structure's CC field.
DELETED Messages with the \Deleted flag set.
DRAFT Messages with the \Draft flag set.
FLAGGED Messages with the \Flagged flag set.
FROM <string> Messages that contain the specified string in the
envelope structure's FROM field.
HEADER <field-name> <string>
Messages that have a header with the specified
field-name (as defined in RFC 822) and that
contains the specified string in the RFC 822
field-body.
KEYWORD <flag> Messages with the specified keyword set.
LARGER <n> Messages with an RFC822.SIZE larger than the
specified number of octets.
NEW Messages that have the \Recent flag set but not the
\Seen flag. This is functionally equivalent to
"(RECENT UNSEEN)".
NOT <search-key>
Messages that do not match the specified search
key.
OLD Messages that do not have the \Recent flag set.
This is functionally equivalent to "NOT RECENT" (as
opposed to "NOT NEW").
ON <date> Messages whose internal date is within the
specified date.
OR <search-key1> <search-key2>
Messages that match either search key.
RECENT Messages that have the \Recent flag set.
SEEN Messages that have the \Seen flag set.
SENTBEFORE <date>
Messages whose RFC 822 Date: header is earlier than
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the specified date.
SENTON <date> Messages whose RFC 822 Date: header is within the
specified date.
SENTSINCE <date>
Messages whose RFC 822 Date: header is within or
later than the specified date.
SINCE <date> Messages whose internal date is within or later
than the specified date.
SMALLER <n> Messages with an RFC822.SIZE smaller than the
specified number of octets.
SUBJECT <string>
Messages that contain the specified string in the
envelope structure's SUBJECT field.
TEXT <string> Messages that contain the specified string in the
header or body of the message.
TO <string> Messages that contain the specified string in the
envelope structure's TO field.
UID <sequence> Messages with unique identifiers within the
specified unique identifier sequence range.
UNANSWERED Messages that do not have the \Answered flag set.
UNDELETED Messages that do not have the \Deleted flag set.
UNDRAFT Messages that do not have the \Draft flag set.
UNFLAGGED Messages that do not have the \Flagged flag set.
UNKEYWORD <flag>
Messages that do not have the specified keyword
set.
UNSEEN Messages that do not have the \Seen flag set.
Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
S: * SEARCH 2 84 882
S: A282 OK SEARCH completed
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5.4.5. FETCH Command
Arguments: message sequence
message data item names
Data: 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 may be either a single atom
or a parenthesized list. The currently defined data items that
can be fetched are:
ALL Macro equivalent to: (FLAGS INTERNALDATE
RFC822.SIZE ENVELOPE)
BODY Non-extensible form of BODYSTRUCTURE.
BODY[<section>]
The text of a particular body section. The section
specification is a set of one or more part numbers
delimited by periods.
Single-part messages only have a part 1.
Multipart messages are assigned consecutive part
numbers, as they occur in the message. If a
particular part is of type message or multipart,
its parts must be indicated by a period followed by
the part number within that nested multipart part.
It is not permitted to fetch a multipart part
itself, only its individual members.
A part of type MESSAGE and subtype RFC822 also has
nested parts. These are the parts of the MESSAGE
part's body. Nested part 0 of a part of type
MESSAGE and subtype RFC822 is the RFC 822 header of
the message.
Every message has at least one part.
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Here is an example of a complex message
with its associated section
specifications:
0 (RFC 822 header of the message)
MULTIPART/MIXED
1 TEXT/PLAIN
2 APPLICATION/OCTET-STREAM
3 MESSAGE/RFC822
3.0 (RFC 822 header of the message)
3.1 TEXT/PLAIN
3.2 APPLICATION/OCTET-STREAM
MULTIPART/MIXED
4.1 IMAGE/GIF
4.2 MESSAGE/RFC822
4.2.0 (RFC 822 header of the message)
4.2.1 TEXT/PLAIN
MULTIPART/ALTERNATIVE
4.2.2.1 TEXT/PLAIN
4.2.2.2 TEXT/RICHTEXT
Note that there is no section
specification for the Multi-part parts
(no section 4 or 4.2.2).
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>]
An alternate form of BODY[section] that does not
implicitly set the \Seen flag.
BODYSTRUCTURE The MIME body structure of the message. This is
computed by the server by parsing the MIME header
lines.
ENVELOPE The envelope structure of the message. This is
computed by the server by parsing the RFC 822
header into the component parts, defaulting various
fields as necessary.
FAST Macro equivalent to: (FLAGS INTERNALDATE
RFC822.SIZE)
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FLAGS The flags that are set for this message.
FULL Macro equivalent to: (FLAGS INTERNALDATE
RFC822.SIZE ENVELOPE BODY)
INTERNALDATE The date and time of final delivery of the message
as defined by RFC 821.
RFC822 The message in RFC 822 format. The \Seen flag is
implicitly set; if this causes the flags to change
they should be included as part of the fetch
responses. This is the concatenation of
RFC822.HEADER and RFC822.TEXT.
RFC822.PEEK An alternate form of RFC822 that does not
implicitly set the \Seen flag.
RFC822.HEADER The RFC 822 format header of the message as stored
on the server including the delimiting blank line
between the header and the body.
RFC822.HEADER.LINES <header-list>
All header lines (including continuation lines) of
the RFC 822 format header of the message with a
field-name (as defined in RFC 822) that matches any
of the strings in header_list. The matching is
case-insensitive but otherwise exact. The
delimiting blank line between the header and the
body is always included.
RFC822.HEADER.LINES.NOT <header-list>
All header lines (including continuation lines) of
the RFC 822 format header of the message with a
field-name (as defined in RFC 822) that does not
match any of the strings in header_list. The
matching is case-insensitive but otherwise exact.
The delimiting blank line between the header and
the body is always included.
RFC822.SIZE The number of octets in the message, as expressed
in RFC 822 format.
RFC822.TEXT The text body of the message, omitting the RFC 822
header. The \Seen flag is implicitly set; if this
causes the flags to change they should be included
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as part of the fetch responses.
RFC822.TEXT.PEEK
An alternate form of RFC822.TEXT that does not
implicitly set the \Seen flag.
UID The unique identifier for the message.
Example: C: A654 FETCH 2:4 (FLAGS RFC822.HEADER.LINES (DATE FROM))
S: * 2 FETCH ....
S: * 3 FETCH ....
S: * 4 FETCH ....
S: A003 OK FETCH completed
5.4.6. PARTIAL Command
Arguments: message number
message data item name
position of first octet
number of octets
Data: untagged responses: FETCH
Result: OK - partial completed
NO - partial error: can't fetch that data
BAD - command unknown or arguments invalid
The PARTIAL command is equivalent to the associated FETCH command,
with the added functionality that only the specified number of
octets, beginning at the specified starting octet, are returned.
Only a single message can be fetched at a time. The first octet
of a message, and hence the minimum for the starting octet, is
octet 1.
The following FETCH items are valid data for PARTIAL: RFC822,
RFC822.HEADER, RFC822.TEXT, BODY[section], as well as any .PEEK
forms of these.
Any partial fetch that attempts to read beyond the end of the text
is truncated as appropriate. If the starting octet is beyond the
end of the text, an empty string is returned.
The data are returned with the FETCH response. There is no
indication of the range of the partial data in this response. It
is not possible to stream multiple PARTIAL commands of the same
data item without processing and synchronizing at each step, since
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streamed commands may be executed out of order.
There is no requirement that partial fetches follow any sequence.
For example, if a partial fetch of octets 1 through 10000 breaks
in an awkward place for BASE64 decoding, it is permitted to
continue with a partial fetch of 9987 through 19987, etc.
The handling of the \Seen flag is the same as in the associated
FETCH command.
Example: C: A005 PARTIAL 4 RFC822 1 1024
S: * 1 FETCH (RFC822 {1024}
S: Return-Path: <gray@cac.washington.edu>
S: ...
S: ......... FLAGS (\Seen))
S: A005 OK PARTIAL completed
5.4.7. STORE Command
Arguments: message sequence
message data item name
value for message data item
Data: 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.
The currently defined data items that can be stored are:
FLAGS <flag list>
Replace the flags for the message with the
argument. The new value of the flags are returned
as if a FETCH of those flags was done.
FLAGS.SILENT <flag list>
Equivalent to FLAGS, but without returning a new
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value.
+FLAGS <flag list>
Add the argument to the flags for the message. The
new value of the flags are 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 are 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
5.4.8. COPY Command
Arguments: message sequence
mailbox name
Data: no specific data 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 specified
destination mailbox. The flags and internal date of the
message(s) SHOULD be preserved in the copy.
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 special information token "[TRYCREATE]" as
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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
5.4.9. UID Command
Arguments: command name
command arguments
Data: untagged responses: FETCH, SEARCH
Result: OK - UID command completed
NO - UID command error
BAD - command unknown or arguments invalid
The UID command takes as its arguments a COPY, FETCH, SEARCH, or
STORE command with arguments appropriate for the associated
command. However, instead of message numbers, it uses unique
identifiers in the sequence argument to reference a particular
message or range of messages. The unique identifier of a message
is guaranteed not to refer to any other message in the mailbox.
Unlike sequence numbers, unique identifiers persist across
sessions. This permits a client to resynchronize its state from a
previous session with the server (e.g. disconnected or offline
access clients).
Sequence ranges are permitted; however, there is no guarantee that
unique identifiers be contiguous. A non-existent unique
identifier within a sequence range is ignored without any error
message generated.
The number after the "*" in an untagged FETCH response is always a
message 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 UID was specified as a
message data item to the FETCH.
The numbers returned in a SEARCH response for a UID SEARCH command
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are unique identifiers.
Example: C: A003 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 UID FETCH completed
5.5. Client Commands - Experimental/Expansion
5.5.1. X<atom> Command
Arguments: implementation defined
Data: 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, or a standard
or standards-track revision of this specification, 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: A442 XPIG-LATIN
S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
S: A442 OK XPIG-LATIN ompleted-cay
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6. Server Responses
Server responses are in three forms: status responses, server data,
and command continuation request.
An untagged response is indicated by the token "*" instead of a tag.
For historical reasons, untagged responses are also called
"unsolicited data", although strictly speaking only unilateral server
data is truly "unsolicited".
Status responses that are tagged indicate the completion result of a
client command, and have a tag matching the command. Untagged status
responses indicate server greeting, or server status that does not
indicate the completion of a command.
Server data are untagged. These are sent as a result of certain
client operations, or unilaterally. There is no syntactic difference
between server data that resulted from a specific command and server
data that were sent unilaterally.
An example of unilateral untagged responses occurs when the IMAP
connection is in selected state. In selected state, the server
checks the mailbox for new messages as part of the execution of each
command. 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.
6.1. Server Responses - Status Responses
Status responses may contain an optional special information token.
A special information token consists of data inside square brackets,
and and contains additional information or status codes for client
software. The currently defined special information tokens are:
ALERT The human-readable text contains a special alert
that MUST be presented to the user in a fashion
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that calls the user's attention to the message.
PARSE The human-readable text represents an error in
parsing the RFC 822 or MIME headers of a message in
the mailbox.
PERMANENTFLAGS Followed by a list of flags, indicates which of the
known flags that the client may 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 reject it with a NO reply or
store the state for the remainder of the current
session only. The PERMANENTFLAGS list may 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 may succeed if the mailbox is first
created by the CREATE command.
UNSEEN Followed by a decimal number, indicates the number
of the first message without the \Seen flag set.
Other special information tokens defined by particular client or
server implementations should be prefixed with an "X" until they
are added to a revision of this protocol.
6.1.1. OK Response
Data: optional special information token
human-readable text
The OK response indicates an information message from the server.
When tagged, it indicates successful completion of the associated
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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 special information token.
The untagged form is also used as one of three possible greetings
at session startup. It indicates that the session is not yet
authenticated and that a LOGIN command is needed.
Example: S: * OK IMAP4 server ready
C: A001 LOGIN fred blurdybloop
S: * OK [ALERT] System shutdown in 10 minutes
S: A001 OK LOGIN Completed
6.1.2. NO Response
Data: optional special information token
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 may still complete successfully. The human-readable text
describes the condition.
Example: C: A222 COPY 1:2 owatagusiam
S: * NO Disk is 98% full, please delete unnecessary data
S: A222 OK COPY completed
C: A222 COPY 3:200 blurdybloop
S: * NO Disk is 98% full, please delete unnecessary data
S: * NO Disk is 99% full, please delete unnecessary data
S: A222 NO COPY failed: disk is full
6.1.3. BAD Response
Data: optional special information token
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 may also indicate an internal
server failure. The human-readable text describes the condition.
Example: C: ...very long command line...
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S: * BAD Command line too long
C: ...empty line...
S: * BAD Empty command line
C: A443 EXPUNGE
S: * BAD Disk crash, attempting salvage to a new disk!
S: * OK Salvage successful, no data lost
S: A443 OK Expunge completed
6.1.4. PREAUTH Response
Data: optional special information token
human-readable text
The PREAUTH response is always untagged, and is one of three
possible greetings at session startup. It indicates that the
session has already been authenticated by external means and thus
no LOGIN command is needed.
Example: S: * PREAUTH IMAP4 server ready and logged in as Smith
6.1.5. BYE Response
Data: optional special information token
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 may be sent as part of a normal logout sequence, or as a
panic shutdown announcement by the server. It is also used by
some server implementations as an announcement of an inactivity
autologout.
This response is also used as one of three possible greetings at
session startup. It indicates that the server is not willing to
accept a session from this client.
Example: S: * BYE Autologout; idle for too long
6.2. Server Responses - Server and Mailbox Status
These responses are always untagged. This is how server data are
transmitted from the server to the client, often as a result of a
command with the same name.
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6.2.1. CAPABILITY Response
Data: 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 first
name in the capability listing MUST be the atom "IMAP4".
Capability names MUST either begin with "X" or be standard or
standards-track IMAP4 extensions registered with IANA. A server
MUST NOT offer capability names that are not described in a
registered and standardized extension, unless that capability name
is prefixed with an "X".
Client implementations SHOULD NOT require any capability name
other than "IMAP4", and MUST ignore any unknown capability names.
A capability name other than IMAP4 indicates that the server
supports an extension to the IMAP4 protocol. Server responses
MUST conform to this document until the client issues a command
that uses the associated extension to the IMAP4 protocol.
Example: S: * CAPABILITY IMAP4 XPIG-LATIN
6.2.2. LIST Response
Data: name attributes
hierarchy delimiter
name
The LIST response occurs as a result of a LIST command. It
returns a single name that matches the LIST specification. There
may be multiple LIST responses for a single LIST command.
Four name attributes are defined:
\Noinferiors It is not possible for any child levels of
hierarchy to exist under this name; no child levels
exist now and none can be created in the future.
\Noselect It is not possible to use this name as a selectable
mailbox.
\Marked The mailbox has been marked "interesting" by the
server; the mailbox probably contains messages that
have been added since the last time the mailbox was
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selected.
\Unmarked The mailbox does not contain any additional
messages since the last time the mailbox was
selected.
If it is not feasible for the server to determine whether the
mailbox is "interesting" or not, it should not send either \Marked
or \Unmarked.
The hierarchy delimiter is a character used to delimit levels of
hierarchy in a mailbox name. A client may use it to create child
mailboxes, and to search higher or lower levels of naming
hierarchy. All children of a top-level hierarchy node must use
the same separator character. A NIL hierarchy delimiter means
that no hierarchy exists; the name is a "flat" name.
The name represents an unambiguous left-to-right hierarchy, and
MUST be valid for use as a reference in LIST and LSUB commands.
Unless \Noselect is indicated, the name must also be valid as an
argument for commands, such as SELECT, that accept mailbox names.
Example: S: * LIST (\Noselect) "/" ~/Mail/foo
6.2.3. LSUB Response
Data: name attributes
hierarchy delimiter
name
The LSUB response occurs as a result of an LSUB command. It
returns a single name that matches the LSUB specification. There
may be multiple LSUB responses for a single LSUB command. The
data is identical in format to the LIST response.
Example: S: * LSUB () "." #news.comp.mail.misc
6.2.4. MAILBOX Response
Data: name
The MAILBOX response is OBSOLETE. It MUST NOT be transmitted
except in response to the FIND MAILBOXES and FIND ALL.MAILBOXES
commands. Client implementations that do not use these commands
are NOT required to support this response. It is documented here
for the benefit of implementors who may wish to support it for
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compatibility with old client implementations.
This response occurs as a result of the FIND MAILBOXES and FIND
ALL.MAILBOXES commands. It returns a single name that matches the
FIND specification. There are no attributes or hierarchy
delimiter.
Example: S: * MAILBOX blurdybloop
6.2.5. SEARCH Response
Data: zero or more numbers
The SEARCH response occurs as a result of a SEARCH or UID SEARCH
command. The number(s) refer to those messages that match the
search criteria. For SEARCH, these are message sequence numbers;
for UID SEARCH, these are unique identifiers. Each number is
delimited by a space.
Example: S: * SEARCH 2 3 6
6.2.6. FLAGS Response
Data: flag list
The FLAGS response occurs as a result of a SELECT or EXAMINE
command. The flag list is a parenthesized list of flags (at a
minimum, the system-defined flags) that are applicable for this
mailbox. Flags other than the system flags may also exist,
depending on server implementation.
Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
6.3. Server Responses - Message Status
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 either a message sequence number or a message
count.
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6.3.1. EXISTS Response
Data: 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 mail).
Example: S: * 23 EXISTS
6.3.2. RECENT Response
Data: none
The RECENT response reports the number of messages that have
arrived since the previous time a SELECT command was done on this
mailbox. This response occurs as a result of a SELECT or EXAMINE
command, and if the size of the mailbox changes (e.g. new mail).
Example: S: * 5 RECENT
6.3.3. EXPUNGE Response
Data: none
The EXPUNGE response reports that the specified message number has
been permanently removed from the mailbox. The message number for
each successive message in the mailbox is immediately decremented
by 1. For example, if the last 5 messages in a 9-message mailbox
are expunged the client will receive 5 untagged EXPUNGE responses
for message 5.
An EXPUNGE response MUST NOT be sent when no command is in
progress; nor while responding to a FETCH, STORE, or SEARCH
command.
Example: S: * 44 EXPUNGE
6.3.4. FETCH Response
Data: 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. This response occurs as the result of a FETCH or
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STORE command, as well as by unilateral server decision (e.g. flag
updates).
The current data items are:
BODY A form of BODYSTRUCTURE without extension data.
BODY[section] A string expressing the body contents of the
specified section. The string should be
interpreted by the client according to the content
transfer encoding, body type, and subtype.
8-bit textual data is permitted if a character set
identifier is part of the body parameter list for
this section.
Non-textual data such as binary data must be
transfer encoded into a textual form such as BASE64
prior to being sent to the client. To derive the
original binary data, the client must decode the
transfer encoded string.
BODYSTRUCTURE A parenthesized list that describes the body
structure of a message. This is computed by the
server by parsing the RFC 822 header and body into
the component parts, defaulting various fields as
necessary.
Multiple parts are indicated by parenthesis
nesting. Instead of a body type as the first
element of the list there is a nested body. The
second element of the list is the multipart subtype
(mixed, digest, parallel, alternative, etc.).
Extension data follows the multipart subtype.
Extension data is never returned with the BODY
fetch, but may be returned with a BODYSTRUCTURE
fetch. Extension data, if present, must be in the
defined order.
The extension data of a multipart body part are in
the following order:
body parameter list
A parenthesized list of attribute/value pairs
[e.g. (foo bar baz rag) where "bar" is the value
of "foo" and "rag" is the value of "baz"] as
defined in MIME.
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Any following extension data are not yet defined in
this version of the protocol. Such extension data
may consist of zero or more NILs, strings, numbers,
or potentially nested lists of such data. Client
implementations that do a BODYSTRUCTURE fetch MUST
be prepared to accept such extension data. Server
implementations MUST NOT send such extension data
until it has been defined by a revision of this
protocol.
The basic fields of a non-multipart body part are
in the following order:
body type
A string giving the content type name as defined
in MIME
body subtype
A string giving the content subtype name as
defined in MIME
body parameter list
A parenthesized list of attribute/value pairs
[e.g. (foo bar baz rag) where "bar" is the value
of "foo" and "rag" is the value of "baz"] as
defined in MIME.
body id
A string giving the content id as defined in
MIME.
body description
A string giving the content description as
defined in MIME.
body encoding
A string giving the content transfer encoding as
defined in MIME.
body size
A number giving the size of the body in octets.
Note that this size is the size in its transfer
encoding and not the resulting size after any
decoding.
A body type of type MESSAGE and subtype RFC822
contains, immediately after the basic fields, the
envelope structure, body structure, and size in
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text lines of the encapsulated message.
A body type of type TEXT contains, immediately
after the basic fields, the size of the body in
text lines. Note that this size is the size in its
transfer encoding and not the resulting size after
any decoding.
Extension data follows the basic fields and the
type-specific fields listed above. Extension data
is never returned with the BODY fetch, but may be
returned with a BODYSTRUCTURE fetch. Extension
data, if present, must be in the defined order.
The extension data of a non-multipart body part are
in the following order:
body MD5
A string giving the content MD5 value as defined
in MIME
Any following extension data are not yet defined in
this version of the protocol, and would be as
described above under multipart extension data.
ENVELOPE A parenthesized list that describes the envelope
structure of a message. This is computed by the
server by parsing the RFC 822 header into the
component parts, defaulting various fields as
necessary.
The fields of the envelope structure are in the
following order: date, subject, from, sender,
reply-to, to, cc, bcc, in-reply-to, and message-id.
The date, subject, in-reply-to, and message-id
fields are strings. The from, sender, reply-to,
to, cc, and bcc fields are parenthesized lists of
address structures.
An address structure is a parenthesized list that
describes an electronic mail address. The fields
of an address structure are in the following order:
personal name, SMTP (RFC 821) at-domain-list
(source route), mailbox name, and host name.
RFC 822 group syntax is indicated by a special form
of address structure in which the host name field
is NIL. If the mailbox name field is also NIL,
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this is an end of group marker (semi-colon in RFC
822 syntax). If the mailbox name field is non-NIL,
this is a start of group marker, and the mailbox
name field holds the group name phrase.
Any field of an envelope or address structure that
is not applicable is presented as NIL. Note that
the server must default the reply-to and sender
fields from the from field; a client is not
expected to know to do this.
FLAGS A parenthesized list of flags that are set for this
message. This may include keywords as well as the
following system flags:
\Seen Message has been read
\Answered Message has been answered
\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).
as well as the following special flag, which may be
fetched but not stored:
\Recent Message has arrived since the previous
time this mailbox was selected.
INTERNALDATE A string containing the date and time of final
delivery of the message as defined by SMTP (RFC
821).
RFC822 A string expressing the message in RFC 822 format.
The header portion of the message must be 7-bit.
8-bit characters are permitted only in the non-
header portion of the message only if there are
MIME data in the message that identify the
character set of the message.
RFC822.HEADER A string expressing the RFC 822 format header of
the message, including the delimiting blank line
between the header and the body. The entire string
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must be 7-bit; 8-bit characters are not permitted
in headers. RFC822.HEADER is used to return data
for the RFC822.HEADER, RFC822.HEADER.LINES, and
RFC822.HEADER.LINES.NOT FETCH data items. Note
that a blank line is always included regardless of
header line restrictions.
RFC822.SIZE A number expressing the number of octets in the
message in RFC 822 format.
RFC822.TEXT A string expressing the text body of the message,
omitting the RFC 822 header. 8-bit characters are
permitted only if there are MIME data in the
message that identify the character set of the
message.
UID A number expressing the unique identifier of the
message.
Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827)
6.3.5. COPY Response
Data: none
The COPY response is OBSOLETE. It MUST NOT be transmitted by new
server implementations. Client implementations MUST ignore this
response. It is documented here for the benefit of client
implementors who may encounter this response from old server
implementations.
In some experimental versions of this protocol, this response was
returned in response to a COPY command to indicate on a per-
message basis that the message was copied successfully.
Example: S: * 44 COPY
6.3.6. STORE Response
Data: message data
The STORE response is OBSOLETE. It MUST NOT be transmitted by new
server implementations. Client implementations MUST treat this
response as equivalent to the FETCH response. It is documented
here for the benefit of client implementors who may encounter this
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response from old server implementations.
In some experimental versions of this protocol, this response was
returned instead of FETCH in response to a STORE command to report
the new value of the flags.
Example: S: * 69 STORE (FLAGS (\Deleted))
6.4. Server Responses - Command Continuation Request
The command completion 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 AUTHORIZATION 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.
The client is not permitted to send the text of the literal unless
the server indicates that it expects it. This permits the server to
process commands and reject errors on a line-by-line basis.
Example: C: A001 LOGIN SMITH {7}
S: + Ready for additional command text
C: fat man
S: A001 OK LOGIN completed
C: A044 BLURDYBLOOP {102856}
S: A044 BAD No such command as "BLURDYBLOOP"
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7. Sample IMAP4 session
The following is a transcript of an IMAP4 session. A long line in
this sample is broken for editorial clarity.
S: * OK IMAP4 Service Ready
C: a001 login mrc secret
S: a001 OK LOGIN completed
C: a002 select inbox
S: * 18 EXISTS
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * 2 RECENT
S: * OK [UNSEEN 17] Message 17 is the first unseen message
S: a002 OK [READ-WRITE] SELECT completed
C: a003 fetch 12 full
S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "14-Jul-1993 02:44:25 -0700"
RFC822.SIZE 4282 ENVELOPE ("Wed, 14 Jul 1993 02:23:25 -0700 (PDT)"
"IMAP4 WG mtg summary and minutes"
(("Terry Gray" NIL "gray" "cac.washington.edu"))
(("Terry Gray" NIL "gray" "cac.washington.edu"))
(("Terry Gray" NIL "gray" "cac.washington.edu"))
((NIL NIL "imap" "cac.washington.edu"))
((NIL NIL "minutes" "CNRI.Reston.VA.US")
("John Klensin" NIL "KLENSIN" "INFOODS.MIT.EDU")) NIL NIL
"<B27397-0100000@cac.washington.edu>")
BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 92))
S: a003 OK FETCH completed
C: a004 fetch 12 rfc822.header
S: * 12 FETCH (RFC822.HEADER {346}
S: Date: Wed, 14 Jul 1993 02:23:25 -0700 (PDT)
S: From: Terry Gray <gray@cac.washington.edu>
S: Subject: IMAP4 WG mtg summary and minutes
S: To: imap@cac.washington.edu
S: cc: minutes@CNRI.Reston.VA.US, John Klensin <KLENSIN@INFOODS.MIT.EDU>
S: Message-Id: <B27397-0100000@cac.washington.edu>
S: Mime-Version: 1.0
S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
S:
S: )
S: a004 OK FETCH completed
C: a005 store 12 +flags \deleted
S: * 12 FETCH (FLAGS (\Seen \Deleted))
S: a005 OK +FLAGS completed
C: a006 logout
S: * BYE IMAP4 server terminating connection
S: a006 OK LOGOUT completed
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8. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) notation as specified in RFC 822 with one exception; the
delimiter used with the "#" construct is a single space (SPACE) and
not a comma.
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.
Syntax marked as obsolete may be encountered with implementations
written for an earlier version of this protocol (e.g. IMAP2). New
implementations SHOULD accept obsolete syntax as input, but MUST NOT
otherwise use such syntax.
address ::= "(" addr_name SPACE addr_adl SPACE addr_mailbox
SPACE addr_host ")"
addr_adl ::= nstring
addr_host ::= nstring
;; NIL indicates RFC 822 group syntax
addr_mailbox ::= nstring
;; NIL indicates end of RFC 822 group; if non-NIL
;; and addr_host is NIL, holds RFC 822 group name
addr_name ::= nstring
alpha ::= "A" / "B" / "C" / "D" / "E" / "F" / "G" / "H" / "I" /
"J" / "L" / "M" / "N" / "O" / "P" / "Q" / "R" / "S" /
"T" / "U" / "V" / "W" / "X" / "Y" / "Z" /
"a" / "b" / "c" / "d" / "e" / "f" / "g" / "h" / "i" /
"j" / "l" / "m" / "n" / "o" / "p" / "q" / "r" / "s" /
"t" / "u" / "v" / "w" / "x" / "y" / "z" /
;; Case-sensitive
append ::= "APPEND" SPACE mailbox [SPACE flag_list]
[SPACE date_time] SPACE literal
astring ::= atom / string
atom ::= 1*ATOM_CHAR
ATOM_CHAR ::= <any CHAR except atom_specials>
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atom_specials ::= "(" / ")" / "{" / SPACE / CTLs / list_wildcards /
quoted_specials
authenticate ::= "AUTHENTICATE" SPACE auth_type *(CRLF base64)
auth_type ::= atom
base64 ::= *(4base64_CHAR) [base64_terminal]
base64_char ::= alpha / digit / "+" / "/"
base64_terminal ::= (2base64_char "==") / (3base64_char "=")
body ::= "(" body_type_1part / body_type_mpart ")"
body_extension ::= nstring / number / "(" 1#body_extension ")"
;; Future expansion. Client implementations
;; MUST accept body_extension fields. Server
;; implementations MUST NOT generate
;; body_extension fields except as defined by
;; future standard or standards-track
;; revisions of this specification.
body_ext_1part ::= body_fld_md5 [SPACE 1#body_extension]
;; MUST NOT be returned on non-extensible "BODY" fetch
body_ext_mpart ::= body_fld_param [SPACE 1#body_extension]]
;; MUST NOT be returned on non-extensible "BODY" fetch
body_fields ::= body_fld_param SPACE body_fld_id SPACE body_fld_desc
SPACE body_fld_enc SPACE body_fld_octets
body_fld_desc ::= nstring
body_fld_enc ::= (<"> ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
"QUOTED-PRINTABLE") <">) / string
body_fld_id ::= nstring
body_fld_lines ::= number
body_fld_md5 ::= nstring
body_fld_octets ::= number
body_fld_param ::= "(" 1#(string string) ")" / nil
body_fld_subtyp ::= string
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body_type_1part ::= (body_type_basic / body_type_msg / body_type_text)
[SPACE body_ext_1part]
body_type_basic ::= (<"> ("APPLICATION" / "AUDIO" / "IMAGE" / "MESSAGE" /
"VIDEO") <">) / string) SPACE body_fld_subtyp SPACE
body_fields
;; MESSAGE subtype MUST NOT be "RFC822"
body_type_mpart ::= 1*body SPACE body_fld_subtyp [SPACE body_ext_mpart]
body_type_msg ::= <"> "MESSAGE" <"> SPACE <"> "RFC822" <"> SPACE
body_fields SPACE envelope SPACE body SPACE
body_fld_lines
body_type_text ::= <"> "TEXT" <"> SPACE body_fld_subtyp SPACE body_fields
SPACE body_fld_lines
capability ::= atom
;; Must begin with "X" or be registered with IANA
;; as standard or standards-track
CHAR ::= <any 7-bit US-ASCII character except NUL, 0x01 - 0x7f>
CHAR8 ::= <any 8-bit octet except NUL, 0x01 - 0xff>
command ::= tag SPACE (command_any / command_auth /
command_nonauth / command_select) CRLF
;; Modal based on state
command_any ::= "CAPABILITY" / "LOGOUT" / "NOOP" / x_command
;; Valid in all states
command_auth ::= append / create / delete / examine / find / list /
lsub / rename / select / subscribe / unsubscribe /
;; Valid only when in Authenticated or Selected state
command_nonauth ::= login / authenticate
;; Valid only when in Non-Authenticated state
command_select ::= "CHECK" / "CLOSE" / "EXPUNGE" /
copy / fetch / partial / store / uid / search
;; Valid only when in Selected state
continue_req ::= "+" SPACE (resp_text / base64)
copy ::= "COPY" SPACE sequence SPACE mailbox
CR ::= <ASCII CR, carriage return, 0x0C>
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create ::= "CREATE" SPACE mailbox
;; Use of INBOX gives a NO error
CRLF ::= CR LF
CTL ::= <any ASCII control character and DEL, 0x00 - 0x1f, 0x7f>
date ::= date_text / <"> date_text <">
date_day ::= 1*2digit
;; Day of month
date_day_fixed ::= (SPACE digit) / 2digit
;; Fixed-format version of date_day
date_month ::= "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
"Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"
date_text ::= date_day "-" date_month "-" (date_year / date_year_old)
date_year ::= 4digit
date_year_old ::= 2digit
;; OBSOLETE, (year - 1900)
date_time ::= <"> (date_time_new / date_time_old) <">
date_time_new ::= date_day_fixed "-" date_month "-" date_year SPACE
time SPACE zone
date_time_old ::= date_day_fixed "-" date_month "-" date_year_old SPACE
time "-" zone_old
;; OBSOLETE
delete ::= "DELETE" SPACE mailbox
;; Use of INBOX gives a NO error
digit ::= "0" / "1" / "2" / "3" / "4" / "5" / "6" / "7" /
"8" / "9"
envelope ::= "(" env_date SPACE env_subject SPACE env_from SPACE
env_sender SPACE env_reply-to SPACE env_to SPACE
env_cc SPACE env_bcc SPACE env_in-reply-to SPACE
env_message-id ")"
env_bcc ::= "(" 1*address ")" / nil
env_cc ::= "(" 1*address ")" / nil
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env_date ::= nstring
env_from ::= "(" 1*address ")" / nil
env_in-reply-to ::= nstring
env_message-id ::= nstring
env_reply-to ::= "(" 1*address ")" / nil
env_sender ::= "(" 1*address ")" / nil
env_subject ::= nstring
env_to ::= "(" 1*address ")" / nil
examine ::= "EXAMINE" SPACE mailbox
fetch ::= "FETCH" SPACE sequence SPACE ("ALL" / "FULL" /
"FAST" / fetch_att / "(" 1#fetch_att ")")
fetch_att ::= "BODY" / "BODYSTRUCTURE" /
"BODY" [".PEEK"] "[" section "]" / "ENVELOPE" /
"FLAGS" / "INTERNALDATE" / "UID" /
"RFC822" (([".TEXT"] [".PEEK"]) / ".SIZE" /
(".HEADER" [".LINES" [".NOT"] SPACE header_list])
find ::= "FIND" SPACE ["ALL."] "MAILBOXES" SPACE list_mailbox
;; OBSOLETE
flag ::= "\Answered" / "\Flagged" / "\Deleted" / "\Seen" /
"\Draft" / flag_keyword / flag_extension
flag_extension ::= "\" atom
;; Future expansion. Client implementations
;; MUST accept flag_extension flags. Server
;; implementations MUST NOT generate
;; flag_extension flags except as defined by
;; future standard or standards-track
;; revisions of this specification.
flag_keyword ::= atom
flag_list ::= "(" #flag ")"
greeting ::= "*" SPACE (resp_cond_auth / resp_cond_bye) CRLF
header_line ::= astring
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header_list ::= "(" 1#header_line ")"
LF ::= <ASCII LF, line feed, 0x0A>
list ::= "LIST" SPACE mailbox SPACE list_mailbox
list_mailbox ::= 1*(ATOM_CHAR / list_wildcards) / string
list_wildcards ::= "%" / "*"
literal ::= "{" number "}" CRLF 1*CHAR8
;; The number represents the number of CHAR8 octets
login ::= "LOGIN" SPACE userid SPACE password
lsub ::= "LSUB" SPACE mailbox SPACE list_mailbox
mailbox ::= "INBOX" / astring
;; INBOX is case-insensitive. Other names may be
;; case-sensitive depending on implementation.
mailbox_data ::= "FLAGS" SPACE flag_list / "LIST" SPACE mailbox_list /
"LSUB" SPACE mailbox_list / "MAILBOX" SPACE text /
"SEARCH" [SPACE 1#number]
mailbox_list ::= "(" #("\Marked" / "\Noinferiors" / "\Noselect" /
"\Unmarked" / flag_extension) ")" SPACE
(<"> QUOTED_CHAR <"> / nil) SPACE mailbox
message_data ::= number SPACE ("EXISTS" / "RECENT" / "EXPUNGE" /
("FETCH" SPACE msg_fetch) / msg_obsolete)
msg_fetch ::= "(" 1#("BODY" SPACE body / "BODYSTRUCTURE" SPACE body /
"BODY[" section "]" SPACE nstring /
"ENVELOPE" SPACE envelope /
"FLAGS" SPACE "(" #(flag / "\Recent") ")" /
"INTERNALDATE" SPACE date_time /
"RFC822" [".HEADER" / ".TEXT"] SPACE nstring /
"RFC822.SIZE" SPACE number / "UID" SPACE uniqueid) ")"
msg_obsolete ::= "COPY" / ("STORE" SPACE msg_fetch)
;; OBSOLETE untagged data responses
nil ::= "NIL"
nstring ::= string / nil
number ::= 1*digit
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partial ::= "PARTIAL" SPACE number SPACE fetch_att_text SPACE
number SPACE number
password ::= astring
quoted ::= <"> *QUOTED_CHAR <">
QUOTED_CHAR ::= <any TEXT_CHAR except quoted_specials> /
"\" quoted_specials
quoted_specials ::= <"> / "\"
rename ::= "RENAME" SPACE mailbox SPACE mailbox
;; Use of INBOX as a destination gives a NO error
response ::= *response_data response_done
response_data ::= "*" SPACE (resp_cond_state / resp_cond_bye /
mailbox_data / message_data / server_data) CRLF
response_done ::= response_tagged / response_fatal
response_fatal ::= "*" SPACE resp_cond_bye CRLF
response_tagged ::= tag SPACE resp_cond_state CRLF
resp_cond_auth ::= ("OK" / "PREAUTH") SPACE resp_text
;; Authentication condition
resp_cond_bye ::= "BYE" SPACE resp_text
;; Server will disconnect condition
resp_cond_state ::= ("OK" / "NO" / "BAD") SPACE resp_text
;; Status condition
resp_text ::= [resp_token SPACE] (text_1522 / text)
resp_token ::= "[ALERT]" / "[PARSE]" /
"[PERMANENTFLAGS" SPACE "(" #(flag / "\*") ")" "]" /
"[READ-ONLY]" / "[READ-WRITE]" / "[TRYCREATE]" /
"[UNSEEN" SPACE number "]" /
"[" atom [SPACE 1*<any TEXT_CHAR except "]">] "]"
search ::= "SEARCH" SPACE ["CHARSET" SPACE astring SPACE]
search_criteria
;; Character set must be registered with IANA
;; as a MIME character set
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search_criteria ::= 1#search_key
search_key ::= search_new / search_old
search_new ::= "DRAFT" / "HEADER" SPACE header_line SPACE astring /
"LARGER" SPACE number / "NOT" SPACE search_key /
"OR" SPACE search_key SPACE search_key /
"SENTBEFORE" SPACE date / "SENTON" SPACE date /
"SENTSINCE" SPACE date / "SMALLER" SPACE number /
"UID" SPACE sequence / "UNDRAFT" / sequence /
"(" search_criteria ")"
;; New in IMAP4
search_old ::= "ALL" / "ANSWERED" / "BCC" SPACE astring /
"BEFORE" SPACE date / "BODY" SPACE astring /
"CC" SPACE astring / "DELETED" / "FLAGGED" /
"FROM" SPACE astring / "KEYWORD" SPACE flag_keyword /
"NEW" / "OLD" / "ON" SPACE date / "RECENT" / "SEEN" /
"SINCE" SPACE date / "SUBJECT" SPACE astring /
"TEXT" SPACE astring / "TO" SPACE astring /
"UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
"UNKEYWORD" SPACE flag_keyword / "UNSEEN"
;; Defined in RFC-1176
section ::= number ["." section]
select ::= "SELECT" SPACE mailbox
server_data ::= "CAPABILITY" SPACE "IMAP4" [SPACE 1#capability]
sequence ::= sequence_num / (sequence "," sequence) /
(sequence_num ":" sequence_num)
;; Identifies a set of messages. For message
;; numbers, these are consecutive numbers from
;; 1 to the number of messages in the mailbox.
;; Comma delimits individual numbers, colon
;; delimits between two numbers inclusive.
;; Example: 2,4:7,9,12:* is 2,4,5,6,7,9,12,13,
;; 14,15 for a mailbox with 15 messages.
sequence_num ::= number / "*"
;; * is the largest number in use. For message
;; numbers, it is the number of messages in the
;; mailbox. For unique identifiers, it is the
;; unique identifier of the last message in the
;; mailbox.
SPACE ::= <ASCII SP, space, 0x20>
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store ::= "STORE" SPACE sequence SPACE store_att_flags
store_att_flags ::= (["+" / "-"] "FLAGS" [".SILENT"]) SPACE
(flag_list / #flag)
string ::= quoted / literal
subscribe ::= "SUBSCRIBE" [SPACE "MAILBOX"] SPACE mailbox
tag ::= 1*<any ATOM_CHAR except "+">
text ::= 1*TEXT_CHAR
text_1522 ::= "=?" <charset> "?" <encoding> "?" <encoded-text> "?="
;; Syntax defined in RFC 1522
TEXT_CHAR ::= <any CHAR except CR and LF>
time ::= 2digit ":" 2digit ":" 2digit
;; Hours minutes seconds
uid ::= "UID" SPACE (copy / fetch / search / store)
;; Uniqueids used instead of message numbers
uniqueid ::= number
;; Strictly ascending
unsubscribe ::= "UNSUBSCRIBE" [SPACE "MAILBOX"] SPACE mailbox
userid ::= astring
x_command ::= "X" atom <experimental command arguments>
zone ::= ("+" / "-") 4digit
;; Signed four-digit value of hhmm representing
;; hours and minutes west of Greenwich (that is,
;; (the amount that the given time differs from
;; Universal Time). Subtracting the timezone
;; from the given time will give the UT form.
;; The Universal Time zone is "+0000".
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zone_old ::= "UT" / "GMT" / "Z" / ;; +0000
"AST" / "EST" / "CST" / "MST" / ;; -0400 to -0700
"PST" / "YST" / "HST" / "BST" / ;; -0800 to -1100
"ADT" / "EDT" / "CDT" / "MDT" / ;; -0300 to -0600
"PDT" / "YDT" / "HDT" / "BDT" / ;; -0700 to -1000
"A" / "B" / "C" / "D" / "E" / "F" / ;; +0100 to +0600
"G" / "H" / "I" / "K" / "L" / "M" / ;; +0700 to +1200
"N" / "O" / "P" / "Q" / "R" / "S" / ;; -0100 to -0600
"T" / "U" / "V" / "W" / "X" / "Y" ;; -0700 to -1200
;; OBSOLETE
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Appendices
A. Author's Note
This document is a rewrite of earlier documents, and supercedes the
protocol specification in those documents: earlier IMAP4 Internet
drafts, the IMAP2bis Internet drafts, unpublished IMAP2bis.TXT
document, RFC 1176, and RFC 1064.
B. Security Considerations
IMAP4 protocol transactions, including electronic mail data, are sent
in the clear over the network unless the optional privacy protection
is negotiated in the AUTHENTICATE command.
A server error message for an AUTHENTICATE command which fails due to
invalid credentials should not detail why the credentials are
invalid.
Use of the LOGIN command sends passwords in the clear. This can be
avoided by using the AUTHENTICATE command instead.
A server error message for a failing LOGIN command should not specify
that the user name, as opposed to the password, is invalid.
Additional security considerations are discussed in the section
discussing the AUTHENTICATE and LOGIN commands.
C. Author's Address
Mark R. Crispin
Networks and Distributed Computing, JE-30
University of Washington
Seattle, WA 98195
Phone: (206) 543-5762
EMail: MRC@CAC.Washington.EDU
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D. IMAP4 Keyword Index
+FLAGS <flag list> (store command data item) ............... 30
+FLAGS.SILENT <flag list> (store command data item) ........ 30
-FLAGS <flag list> (store command data item) ............... 30
-FLAGS.SILENT <flag list> (store command data item) ........ 30
ALERT (special information token) .......................... 33
ALL (fetch item) ........................................... 25
ALL (search key) ........................................... 22
ANSWERED (search key) ...................................... 22
APPEND (command) ........................................... 18
AUTHENTICATE (command) ..................................... 8
BAD (response) ............................................. 35
BCC <string> (search key) .................................. 22
BEFORE <date> (search key) ................................. 22
BODY (fetch item) .......................................... 25
BODY (fetch result) ........................................ 41
BODY <string> (search key) ................................. 22
BODY.PEEK[<section>] (fetch item) .......................... 26
BODYSTRUCTURE (fetch item) ................................. 26
BODYSTRUCTURE (fetch result) ............................... 41
BODY[<section>] (fetch item) ............................... 25
BODY[section] (fetch result) ............................... 41
BYE (response) ............................................. 36
CAPABILITY (command) ....................................... 6
CAPABILITY (response) ...................................... 37
CC <string> (search key) ................................... 22
CHECK (command) ............................................ 19
CLOSE (command) ............................................ 20
COPY (command) ............................................. 30
COPY (response) ............................................ 45
CREATE (command) ........................................... 12
DELETE (command) ........................................... 12
DELETED (search key) ....................................... 23
DRAFT (search key) ......................................... 23
ENVELOPE (fetch item) ...................................... 26
ENVELOPE (fetch result) .................................... 43
EXAMINE (command) .......................................... 11
EXISTS (response) .......................................... 40
EXPUNGE (command) .......................................... 20
EXPUNGE (response) ......................................... 40
FAST (fetch item) .......................................... 26
FETCH (command) ............................................ 25
FETCH (response) ........................................... 40
FIND ALL.MAILBOXES (command) ............................... 16
FIND MAILBOXES (command) ................................... 17
FLAGGED (search key) ....................................... 23
FLAGS (fetch item) ......................................... 26
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FLAGS (fetch result) ....................................... 44
FLAGS (response) ........................................... 39
FLAGS <flag list> (store command data item) ................ 29
FLAGS.SILENT <flag list> (store command data item) ......... 29
FROM <string> (search key) ................................. 23
FULL (fetch item) .......................................... 27
HEADER <field-name> <string> (search key) .................. 23
INTERNALDATE (fetch item) .................................. 27
INTERNALDATE (fetch result) ................................ 44
KEYWORD <flag> (search key) ................................ 23
LARGER <n> (search key) .................................... 23
LIST (command) ............................................. 14
LIST (response) ............................................ 37
LOGIN (command) ............................................ 9
LOGOUT (command) ........................................... 7
LSUB (command) ............................................. 16
LSUB (response) ............................................ 38
MAILBOX (response) ......................................... 38
NEW (search key) ........................................... 23
NO (response) .............................................. 35
NOOP (command) ............................................. 6
NOT <search-key> (search key) .............................. 23
OK (response) .............................................. 34
OLD (search key) ........................................... 23
ON <date> (search key) ..................................... 23
OR <search-key1> <search-key2> (search key) ................ 23
PARSE (special information token) .......................... 34
PARTIAL (command) .......................................... 28
PERMANENTFLAGS (special information token) ................. 34
PREAUTH (response) ......................................... 36
READ-ONLY (special information token) ...................... 34
READ-WRITE (special information token) ..................... 34
RECENT (response) .......................................... 40
RECENT (search key) ........................................ 23
RENAME (command) ........................................... 13
RFC822 (fetch item) ........................................ 27
RFC822 (fetch result) ...................................... 44
RFC822.HEADER (fetch item) ................................. 27
RFC822.HEADER (fetch result) ............................... 44
RFC822.HEADER.LINES <header-list> (fetch item) ............. 27
RFC822.HEADER.LINES.NOT <header-list> (fetch item) ......... 27
RFC822.PEEK (fetch item) ................................... 27
RFC822.SIZE (fetch item) ................................... 27
RFC822.SIZE (fetch result) ................................. 45
RFC822.TEXT (fetch item) ................................... 27
RFC822.TEXT (fetch result) ................................. 45
RFC822.TEXT.PEEK (fetch item) .............................. 28
SEARCH (command) ........................................... 21
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SEARCH (response) .......................................... 39
SEEN (search key) .......................................... 23
SELECT (command) ........................................... 10
SENTBEFORE <date> (search key) ............................. 23
SENTON <date> (search key) ................................. 24
SENTSINCE <date> (search key) .............................. 24
SINCE <date> (search key) .................................. 24
SMALLER <n> (search key) ................................... 24
STORE (command) ............................................ 29
STORE (response) ........................................... 45
SUBJECT <string> (search key) .............................. 24
SUBSCRIBE (command) ........................................ 14
TEXT <string> (search key) ................................. 24
TO <string> (search key) ................................... 24
TRYCREATE (special information token) ...................... 34
UID (command) .............................................. 31
UID (fetch item) ........................................... 28
UID (fetch result) ......................................... 45
UID <sequence> (search key) ................................ 24
UNANSWERED (search key) .................................... 24
UNDELETED (search key) ..................................... 24
UNDRAFT (search key) ....................................... 24
UNFLAGGED (search key) ..................................... 24
UNKEYWORD <flag> (search key) .............................. 24
UNSEEN (search key) ........................................ 24
UNSEEN (special information token) ......................... 34
UNSUBSCRIBE (command) ...................................... 14
X<atom> (command) .......................................... 32
\Answered (system flag) .................................... 44
\Deleted (system flag) ..................................... 44
\Draft (system flag) ....................................... 44
\Flagged (system flag) ..................................... 44
\Marked (mailbox name attribute) ........................... 37
\Noinferiors (mailbox name attribute) ...................... 37
\Noselect (mailbox name attribute) ......................... 37
\Recent (system flag) ...................................... 44
\Seen (system flag) ........................................ 44
\Unmarked (mailbox name attribute) ......................... 38
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