GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc1730

Network Working Group M. Crispin Request for Comments: 1730 University of Washington Category: Standards Track December 1994

            INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 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 (see also [IMAP-DISC]).
 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 the use of numbers.
 These numbers are either message sequence numbers (relative position
 from 1 to the number of messages in the mailbox) or unique
 identifiers (immutable, strictly ascending values assigned to each
 message, but which are not necessarily contiguous).
 IMAP4 supports a single server.  A mechanism for supporting multiple
 IMAP4 servers is discussed in [IMSP].
 IMAP4 does not specify a means of posting mail; this function is
 handled by a mail transfer protocol such as [SMTP].
 IMAP4 is designed to be upwards compatible from the [IMAP2] protocol.
 Compatibility issues are discussed in [IMAP-COMPAT].

Crispin [Page i] RFC 1730 IMAP4 December 1994

Table of Contents

IMAP4 Protocol Specification ……………………………….. 1 1. Organization of this Document ……………………….. 1 1.1. How to Read This Document …………………………… 1 1.2. Conventions Used in this Document ……………………. 1 2. Protocol Overview ………………………………….. 1 2.1. Link Level ………………………………………… 1 2.2. Commands and Responses ……………………………… 1 2.2.1. Client Protocol Sender and Server Protocol Receiver ……. 2 2.2.2. Server Protocol Sender and Client Protocol Receiver ……. 2 3. State and Flow Diagram ……………………………… 4 3.1. Non-Authenticated State …………………………….. 4 3.2. Authenticated State ………………………………… 4 3.3. Selected State …………………………………….. 4 3.4. Logout State ………………………………………. 4 4. Data Formats ………………………………………. 6 4.1. Atom ……………………………………………… 6 4.2. Number ……………………………………………. 6 4.3. String ……………………………………………. 6 4.3.1. 8-bit and Binary Strings ……………………………. 7 4.4. Parenthesized List …………………………………. 7 4.5. NIL ………………………………………………. 7 5. Operational Considerations ………………………….. 8 5.1. Mailbox Naming …………………………………….. 8 5.2. Mailbox Size and Message Status Updates ………………. 8 5.3. Response when no Command in Progress …………………. 8 5.4. Autologout Timer …………………………………… 9 5.5. Multiple Commands in Progress ……………………….. 9 6. Client Commands ……………………………………. 10 6.1. Client Commands - Any State …………………………. 10 6.1.1. CAPABILITY Command …………………………………. 10 6.1.2. NOOP Command ………………………………………. 11 6.1.3. LOGOUT Command …………………………………….. 11 6.2. Client Commands - Non-Authenticated State …………….. 12 6.2.1. AUTHENTICATE Command ……………………………….. 12 6.2.2. LOGIN Command ……………………………………… 14 6.3. Client Commands - Authenticated State ………………… 14 6.3.1. SELECT Command …………………………………….. 15 6.3.2. EXAMINE Command ……………………………………. 16 6.3.3. CREATE Command …………………………………….. 17 6.3.4. DELETE Command …………………………………….. 18 6.3.5. RENAME Command …………………………………….. 18

Crispin [Page ii] RFC 1730 IMAP4 December 1994

6.3.6. SUBSCRIBE Command ………………………………….. 19 6.3.7. UNSUBSCRIBE Command ………………………………… 19 6.3.8. LIST Command ………………………………………. 20 6.3.9. LSUB Command ………………………………………. 22 6.3.10. APPEND Command …………………………………….. 22 6.4. Client Commands - Selected State …………………….. 23 6.4.1. CHECK Command ……………………………………… 23 6.4.2. CLOSE Command ……………………………………… 24 6.4.3. EXPUNGE Command ……………………………………. 25 6.4.4. SEARCH Command …………………………………….. 25 6.4.5. FETCH Command ……………………………………… 29 6.4.6. PARTIAL Command ……………………………………. 32 6.4.7. STORE Command ……………………………………… 33 6.4.8. COPY Command ………………………………………. 34 6.4.9. UID Command ……………………………………….. 35 6.5. Client Commands - Experimental/Expansion ……………… 37 6.5.1. X<atom> Command ……………………………………. 37 7. Server Responses …………………………………… 38 7.1. Server Responses - Status Responses ………………….. 39 7.1.1. OK Response ……………………………………….. 40 7.1.2. NO Response ……………………………………….. 40 7.1.3. BAD Response ………………………………………. 41 7.1.4. PREAUTH Response …………………………………… 41 7.1.5. BYE Response ………………………………………. 41 7.2. Server Responses - Server and Mailbox Status ………….. 42 7.2.1. CAPABILITY Response ………………………………… 42 7.2.2. LIST Response ……………………………………… 43 7.2.3. LSUB Response ……………………………………… 44 7.2.4. SEARCH Response ……………………………………. 44 7.2.5. FLAGS Response …………………………………….. 44 7.3. Server Responses - Message Status ……………………. 45 7.3.1. EXISTS Response ……………………………………. 45 7.3.2. RECENT Response ……………………………………. 45 7.3.3. EXPUNGE Response …………………………………… 45 7.3.4. FETCH Response …………………………………….. 46 7.3.5. Obsolete Responses …………………………………. 51 7.4. Server Responses - Command Continuation Request ……….. 51 8. Sample IMAP4 session ……………………………….. 52 9. Formal Syntax ……………………………………… 53 10. Author's Note ……………………………………… 64 11. Security Considerations …………………………….. 64 12. Author's Address …………………………………… 64 Appendices ……………………………………………….. 65 A. Obsolete Commands ………………………………….. 65 A.6.3.OBS.1. FIND ALL.MAILBOXES Command …………………… 65 A.6.3.OBS.2. FIND MAILBOXES Command ………………………. 65 A.6.3.OBS.3. SUBSCRIBE MAILBOX Command ……………………. 66 A.6.3.OBS.4. UNSUBSCRIBE MAILBOX Command ………………….. 66

Crispin [Page iii] RFC 1730 IMAP4 December 1994

B. Obsolete Responses …………………………………. 68 B.7.2.OBS.1. MAILBOX Response ……………………………. 68 B.7.3.OBS.1. COPY Response ………………………………. 68 B.7.3.OBS.2. STORE Response ……………………………… 69 C. References ………………………………………… 70 E. IMAP4 Keyword Index ………………………………… 71

Crispin [Page iv] RFC 1730 IMAP4 December 1994

IMAP4 Protocol Specification

1. Organization of this Document

1.1. How to Read This Document

 This document is written from the point of view of the implementor of
 an IMAP4 client or server.  Beyond the protocol overview in section
 2, it is not optimized for someone trying to understand the operation
 of the protocol.  The material in sections 3 through 5 provides the
 general context and definitions with which IMAP4 operates.
 Sections 6, 7, and 9 describe the IMAP commands, responses, and
 syntax, respectively.  The relationships among these are such that it
 is almost impossible to understand any of them separately.  In
 particular, one should not attempt to deduce command syntax from the
 command section alone; one should instead refer to the formal syntax
 section.

1.2. Conventions Used in this Document

 In examples, "C:" and "S:" indicate lines sent by the client and
 server respectively.

2. Protocol Overview

2.1. Link Level

 The IMAP4 protocol assumes a reliable data stream such as provided by
 TCP.  When TCP is used, an IMAP4 server listens on port 143.

2.2. Commands and Responses

 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.
 All interactions transmitted by client and server are in the form of
 lines; that is, strings that end with a CRLF.  The protocol receiver
 of an IMAP4 client or server is either reading a line, or is reading
 a sequence of octets with a known count followed by a line.

Crispin [Page 1] RFC 1730 IMAP4 December 1994

2.2.1. Client Protocol Sender and Server Protocol Receiver

 The client command begins an 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.
 There are two cases in which a line from the client does not
 represent a complete command.  In one case, a command argument is
 quoted with an octet count (see the description of literal in String
 under Data Formats); in the other case, the command arguments require
 server feedback (see the AUTHENTICATE command).  In either case, the
 server sends a command continuation request response if it is ready
 for the octets (if appropriate) and the remainder of the command.
 This response is prefixed with the token "+".
      Note: If, instead, the server detected an error in the
      command, it sends a BAD completion response with tag
      matching the command (as described below) to reject the
      command and prevent the client from sending any more of the
      command.
      It is also possible for the server to send a completion
      response for some other command (if multiple commands are
      in progress), or untagged data.  In either case, the
      command continuation request is still pending; the client
      takes the appropriate action for the response, and reads
      another response from the server.
 The protocol receiver of an IMAP4 server reads a command line from
 the client, parses the command and its arguments, and transmits
 server data and a server command completion result response.

2.2.2. Server Protocol Sender and Client Protocol Receiver

 Data transmitted by the server to the client and status responses
 that do not indicate command completion are prefixed with the token
 "*", and are called untagged responses.
 Server data may be sent as a result of a client command, or may be
 sent unilaterally by the server.  There is no syntactic difference
 between server data that resulted from a specific command and server
 data that were sent unilaterally.
 The server completion result response indicates the success or
 failure of the operation.  It is tagged with the same tag as the
 client command which began the operation.  Thus, if more than one

Crispin [Page 2] RFC 1730 IMAP4 December 1994

 command is in progress, the tag in a server completion response
 identifies the command to which the response applies.  There are
 three possible server completion responses: OK (indicating success),
 NO (indicating failure), or BAD (indicating protocol error such as
 unrecognized command or command syntax error).
 The protocol receiver of an IMAP4 client reads a response line from
 the server.  It then takes action on the response based upon the
 first token of the response, which may be a tag, a "*", or a "+".  As
 described above.
 A client MUST be prepared to accept any server response at all times.
 This includes server data that it may not have requested.  Server
 data SHOULD be recorded, so that the client can reference its
 recorded copy rather than sending a command to the server to request
 the data.  In the case of certain server data, recording the data is
 mandatory.
 This topic is discussed in greater detail in the Server Responses
 section.

Crispin [Page 3] RFC 1730 IMAP4 December 1994

3. State and Flow Diagram

 An IMAP4 server is in one of four states.  Most commands are valid in
 only certain states.  It is a protocol error for the client to
 attempt a command while the command is in an inappropriate state.  In
 this case, a server will respond with a BAD or NO (depending upon
 server implementation) command completion result.

3.1. 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.

3.2. 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.

3.3. Selected State

 In selected state, a mailbox has been selected to access.  This state
 is entered when a mailbox has been successfully selected.

3.4. 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.

Crispin [Page 4] RFC 1730 IMAP4 December 1994

          +--------------------------------------+
          |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

Crispin [Page 5] RFC 1730 IMAP4 December 1994

4. Data Formats

 IMAP4 uses textual commands and responses.  Data in IMAP4 can be in
 one of several forms: atom, number, string, parenthesized list, or
 NIL.

4.1. Atom

 An atom consists of one or more non-special characters.

4.2. Number

 A number consists of one or more digit characters, and represents a
 numeric value.

4.3. String

 A string is in one of two forms: literal and quoted string.  The
 literal form is the general form of string.  The quoted string form
 is an alternative that avoids the overhead of processing a literal at
 the cost of restrictions of what may be in a quoted string.
 A literal is a sequence of zero or more octets (including CR and LF),
 prefix-quoted with an octet count in the form of an open brace ("{"),
 the number of octets, close brace ("}"), and CRLF.  In the case of
 literals transmitted from server to client, the CRLF is immediately
 followed by the octet data.  In the case of literals transmitted from
 client to server, the client must wait to receive a command
 continuation request (described later in this document) before
 sending the octet data (and the remainder of the command).
 A quoted string is a sequence of zero or more 7-bit characters,
 excluding CR and LF, with double quote (<">) characters at each end.
 The empty string is respresented as either "" (a quoted string with
 zero characters between double quotes) or as {0} followed by CRLF (a
 literal with an octet count of 0).
      Note: Even if the octet count is 0, a client transmitting a
      literal must wait to receive a command continuation
      request.

Crispin [Page 6] RFC 1730 IMAP4 December 1994

4.3.1. 8-bit and Binary Strings

 8-bit textual and binary mail is supported through the use of
 [MIME-1] encoding.  IMAP4 implementations MAY transmit 8-bit or
 multi-octet characters in literals, but should do so only when the
 character set is identified.
 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.

4.4. Parenthesized List

 Data structures are represented as a "parenthesized list"; a sequence
 of data items, delimited by space, and bounded at each end by
 parentheses.  A parenthesized list may itself contain other
 parenthesized lists, using multiple levels of parentheses to indicate
 nesting.
 The empty list is represented as () -- a parenthesized list with no
 members.

4.5. NIL

 The special atom "NIL" represents the non-existence of a particular
 data item that is represented as a string or parenthesized list, as
 distinct from the empty string "" or the empty parenthesized list ().

Crispin [Page 7] RFC 1730 IMAP4 December 1994

5. Operational Considerations

5.1. Mailbox Naming

 The interpretation of mailbox names is implementation-dependent.
 However, the mailbox name INBOX is a special name reserved to mean
 "the primary mailbox for this user on this server".  If it is desired
 to export hierarchical mailbox names, mailbox names must be
 left-to-right hierarchical using a single character to separate
 levels of hierarchy.  The same hierarchy separator character is used
 for all levels of hierarchy within a single name.

5.2. Mailbox Size and Message Status Updates

 At any time, a server can send data that the client did not request.
 Sometimes, such behavior is required.  For example, agents other than
 the server may add messages to the mailbox (e.g. new mail delivery),
 change the flags of message in the mailbox (e.g. simultaneous access
 to the same mailbox by multiple agents), or even remove messages from
 the mailbox.  A server MUST send mailbox size updates automatically
 if a mailbox size change is observed during the processing of a
 command.  A server SHOULD send message flag updates automatically,
 without requiring the client to request such updates explicitly.
 Special rules exist for server notification of a client about the
 removal of messages to prevent synchronization errors; see the
 description of the EXPUNGE response for more details.
 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.

5.3. Response when no Command in Progress

 Server implementations are permitted to send an untagged response
 (except for EXPUNGE) while there is no command in progress.  Server
 implementations that send such responses MUST deal with flow control
 considerations.  Specifically, they must either (1) verify that the
 size of the data does not exceed the underlying transport's available
 window size, or (2) use non-blocking writes.

Crispin [Page 8] RFC 1730 IMAP4 December 1994

5.4. 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.

5.5. Multiple Commands in Progress

 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.

Crispin [Page 9] RFC 1730 IMAP4 December 1994

6. Client Commands

 IMAP4 commands are described in this section.  Commands are organized
 by the state in which the command is permitted.  Commands which are
 permitted in multiple states are listed in the minimum permitted
 state (for example, commands valid in authenticated and selected
 state are listed in the authenticated state commands).
 Command arguments, identified by "Arguments:" in the command
 descriptions below, are described by function, not by syntax.  The
 precise syntax of command arguments is described in the Formal Syntax
 section.
 Some commands cause specific server data to be returned; these are
 identified by "Data:" in the command descriptions below.  See the
 response descriptions in the Responses section for information on
 these responses, and the Formal Syntax section for the precise syntax
 of these responses.  It is possible for server data to be transmitted
 as a result of any command; thus, commands that do not specifically
 require server data specify "no specific data for this command"
 instead of "none".
 The "Result:" in the command description refers to the possible
 tagged status responses to a command, and any special interpretation
 of these status responses.

6.1. Client Commands - Any State

 The following commands are valid in any state: CAPABILITY, NOOP, and
 LOGOUT.

6.1.1. 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.  This listing of capabilities is
    not dependent upon connection state or user.  It is therefore not
    necessary to issue a CAPABILITY command more than once in a
    session.

Crispin [Page 10] RFC 1730 IMAP4 December 1994

    Capability names other than "IMAP4" refer to extensions,
    revisions, or amendments to this specification.  See the
    documentation of the CAPABILITY response for additional
    information.  No capabilities are enabled without explicit client
    action to invoke the capability.  See the section entitled "Client
    Commands - Experimental/Expansion" for information about the form
    of site or implementation-specific capabilities.
 Example:    C: abcd CAPABILITY
             S: * CAPABILITY IMAP4
             S: abcd OK CAPABILITY completed

6.1.2. 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
             S: * 23 EXISTS
             S: * 3 RECENT
             S: * 14 FETCH (FLAGS (\Seen \Deleted))
             S: a047 OK NOOP completed

Crispin [Page 11] RFC 1730 IMAP4 December 1994

6.1.3. 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)

6.2. 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.

Crispin [Page 12] RFC 1730 IMAP4 December 1994

6.2.1. 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,
    such as described in [IMAP-AUTH], 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

Crispin [Page 13] RFC 1730 IMAP4 December 1994

    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.

6.2.2. 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

6.3. 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.

Crispin [Page 14] RFC 1730 IMAP4 December 1994

 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,
 and APPEND.

6.3.1. 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
       OK [UIDVALIDITY <n>]
                   The unique  identifier  validity  value.   See  the
                   description of the UID command for more detail.
    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 response code in an OK
    untagged response, indicating the message 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 response code 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

Crispin [Page 15] RFC 1730 IMAP4 December 1994

    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
    prefix the text of the tagged OK response with the "[READ-WRITE]"
    response code.
    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 tagged OK response to
    SELECT with the "[READ-ONLY]" response code.  Read-only access
    through SELECT differs from the EXAMINE command in that certain
    read-only mailboxes may permit the change of permanent state on a
    per-user (as opposed to global) basis.  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: * OK [UIDVALIDITY 3857529045] UIDs valid
             S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
             S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
             S: A142 OK [READ-WRITE] SELECT completed

6.3.2. 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.

Crispin [Page 16] RFC 1730 IMAP4 December 1994

    The text of the tagged OK response to the EXAMINE command MUST
    begin with the "[READ-ONLY]" response code.
 Example:    C: A932 EXAMINE blurdybloop
             S: * 17 EXISTS
             S: * 2 RECENT
             S: * OK [UNSEEN 8] Message 8 is first unseen
             S: * OK [UIDVALIDITY 3857529045] UIDs valid
             S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
             S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
             S: A932 OK [READ-ONLY] EXAMINE completed

6.3.3. 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 tagged NO response.
    If the mailbox name is suffixed with the server's hierarchy
    separator character (as returned from the server by a LIST
    command), this is a declaration that the client may, in the
    future, create mailbox names under this name in the hierarchy.
    Server implementations that do not require this declaration MUST
    ignore it.
    If a new mailbox is created with the same name as a mailbox which
    was deleted, its unique identifiers MUST be greater than any
    unique identifiers used in the previous incarnation of the mailbox
    UNLESS the new incarnation has a different unique identifier
    validity value.  See the description of the UID command for more
    detail.
 Example:    C: A003 CREATE owatagusiam/
             S: A003 OK CREATE completed
             C: A004 CREATE owatagusiam/blurdybloop
             S: A004 OK CREATE completed

Crispin [Page 17] RFC 1730 IMAP4 December 1994

      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.

6.3.4. 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.  A tagged OK response is returned only if the mailbox has
    been deleted.  It is an error to attempt to delete INBOX or a
    mailbox name that does not exist.  Any error in deletion will
    return a tagged NO response.
    The value of the highest-used unique indentifier of the deleted
    mailbox MUST be preserved so that a new mailbox created with the
    same name will not reuse the identifiers of the former
    incarnation, UNLESS the new incarnation has a different unique
    identifier validity value.  See the description of the UID command
    for more detail.
 Example:    C: A683 DELETE blurdybloop
             S: A683 OK DELETE completed

6.3.5. 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

Crispin [Page 18] RFC 1730 IMAP4 December 1994

    The RENAME command changes the name of a mailbox.  A tagged OK
    response is returned only if the mailbox has been renamed.  It is
    an error to attempt to rename from a mailbox name that does not
    exist or to a mailbox name that already exists.  Any error in
    renaming will return a tagged NO response.
    Renaming INBOX is permitted; a new, empty INBOX is created in its
    place.
 Example:    C: Z4S9 RENAME blurdybloop owatagusiam
             S: Z4S9 OK RENAME completed

6.3.6. 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 set of "active" or "subscribed" mailboxes as returned by
    the LSUB command.  This command returns a tagged OK response only
    if the subscription is successful.
 Example:    C: A002 SUBSCRIBE #news.comp.mail.mime
             S: A002 OK SUBSCRIBE completed

6.3.7. 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 set of "active" or "subscribed" mailboxes as returned
    by the LSUB command.  This command returns a tagged OK response
    only if the unsubscription is successful.

Crispin [Page 19] RFC 1730 IMAP4 December 1994

 Example:    C: A002 UNSUBSCRIBE #news.comp.mail.mime
             S: A002 OK UNSUBSCRIBE completed

6.3.8. 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 name 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 name 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 interpreted, in an
    implementation-dependent fashion, into a canonical form that
    represents an unambiguous left-to-right hierarchy.  The returned
    mailbox names will be in the interpreted form.
    Any part of the reference argument that is included in the
    interpreted form SHOULD prefix the interpreted form.  It should
    also be in the same form as the reference name argument.  This
    rule permits the client to determine if the returned mailbox name
    is in the context of the reference argument, or if something about
    the mailbox argument overrode the reference argument.  Without
    this rule, the client would have to have knowledge of the server's
    naming semantics including what characters are "breakouts" that
    override a naming context.

Crispin [Page 20] RFC 1730 IMAP4 December 1994

         For example, 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.*
             archive/      %             archive/%
             #news.        comp.mail.*   #news.comp.mail.*
             ~smith/Mail/  /usr/doc/foo  /usr/doc/foo
             archive/      ~fred/Mail/*  ~fred/Mail/*
         The first three examples demonstrate interpretations in
         the context of the reference argument.  Note that
         "~smith/Mail" should not be transformed into something
         like "/u2/users/smith/Mail", or it would be impossible
         for the client to determine that the interpretation was
         in the context of the reference.
    The character "*" is a wildcard, and matches zero or more
    characters at this position.  The character "%" is similar to "*",
    but it does not match a hierarchy delimiter.  If the "%" wildcard
    is the last character of a mailbox name argument, matching levels
    of hierarchy are also returned.  If these levels of hierarchy are
    not also selectable mailboxes, they are returned with the
    \Noselect mailbox name attribute (see the description of the LIST
    response for more detail).
    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

Crispin [Page 21] RFC 1730 IMAP4 December 1994

6.3.9. 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

6.3.10. APPEND Command

 Arguments:  mailbox name
             optional flag parenthesized 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-1] encoding.
    If a flag parenthesized 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.

Crispin [Page 22] RFC 1730 IMAP4 December 1994

    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.
    If the destination mailbox does not exist, a server MUST return an
    error, and MUST NOT automatically create the mailbox.  Unless it
    is certain that the destination mailbox can not be created, the
    server MUST send the response code "[TRYCREATE]" as the prefix of
    the text of the tagged NO response.  This gives a hint to the
    client that it can attempt a CREATE command and retry the APPEND
    if the CREATE is successful.
 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]
      envelope information.

6.4. 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.

Crispin [Page 23] RFC 1730 IMAP4 December 1994

6.4.1. 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
    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

6.4.2. 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,

Crispin [Page 24] RFC 1730 IMAP4 December 1994

    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

6.4.3. 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.
 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.  See the description of the EXPUNGE
      response for further explanation.

Crispin [Page 25] RFC 1730 IMAP4 December 1994

6.4.4. 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 sequence numbers corresponding to
    those messages that match the searching criteria.
    When multiple keys are specified, the result is the intersection
    (AND function) of all the messages that match those keys.  For
    example, the criteria DELETED 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-1] 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.  [MIME-2] strings that appear in RFC 822/MIME
    message headers, and [MIME-1] 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.

Crispin [Page 26] RFC 1730 IMAP4 December 1994

    The defined search keys are as follows.  Refer to the Formal
    Syntax section for the precise syntactic definitions of the
    arguments.
    <message set>  Messages with message sequence numbers
                   corresponding to the specified message sequence
                   number set
    ALL            All messages in the mailbox; the default initial
                   key for ANDing.
    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
                   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)".

Crispin [Page 27] RFC 1730 IMAP4 December 1994

    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 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 <message set>
                   Messages with unique identifiers corresponding to
                   the specified unique identifier set.

Crispin [Page 28] RFC 1730 IMAP4 December 1994

    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

6.4.5. FETCH Command

 Arguments:  message set
             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.

Crispin [Page 29] RFC 1730 IMAP4 December 1994

                   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.
                        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.

Crispin [Page 30] RFC 1730 IMAP4 December 1994

    BODYSTRUCTURE  The [MIME-1] body structure of the message.  This
                   is computed by the server by parsing the [MIME-1]
                   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)
    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.

Crispin [Page 31] RFC 1730 IMAP4 December 1994

    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 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

6.4.6. PARTIAL Command

 Arguments:  message sequence 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

Crispin [Page 32] RFC 1730 IMAP4 December 1994

    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
    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

6.4.7. STORE Command

 Arguments:  message set
             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

Crispin [Page 33] RFC 1730 IMAP4 December 1994

    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
                   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.
  1. 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.
  1. 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

Crispin [Page 34] RFC 1730 IMAP4 December 1994

6.4.8. COPY Command

 Arguments:  message set
             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 response code "[TRYCREATE]" as the prefix of
    the text of the tagged NO response.  This gives a hint to the
    client that it can attempt a CREATE command and retry the COPY if
    the CREATE is successful.
    If the COPY command is unsuccessful for any reason, server
    implementations MUST restore the destination mailbox to its state
    before the COPY attempt.
 Example:    C: A003 COPY 2:4 MEETING
             S: A003 OK COPY completed

6.4.9. 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 has two forms.  In the first form, it takes as its
    arguments a COPY, FETCH, or STORE command with arguments
    appropriate for the associated command.  However, the numbers in
    the message set argument are unique identifiers instead of message
    sequence numbers.

Crispin [Page 35] RFC 1730 IMAP4 December 1994

    In the second form, the UID command takes a SEARCH command with
    SEARCH command arguments.  The interpretation of the arguments is
    the same as with SEARCH; however, the numbers returned in a SEARCH
    response for a UID SEARCH command are unique identifiers instead
    of message sequence numbers.  For example, the command UID SEARCH
    1:100 UID 443:557 returns the unique identifiers corresponding to
    the intersection of the message sequence number set 1:100 and the
    UID set 443:557.
    A unique identifier of a message is a number, and is guaranteed
    not to refer to any other message in the mailbox.  Unique
    identifiers are assigned in a strictly ascending fashion for each
    message added to the mailbox.  Unlike message 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); this is discussed
    further in [IMAP-DISC].
    Associated with every mailbox is a unique identifier validity
    value, which is sent in an UIDVALIDITY response code in an OK
    untagged response at message selection time.  If unique
    identifiers from an earlier session fail to persist to this
    session, the unique identifier validity value MUST be greater than
    in the earlier session.
         Note: An example of a good value to use for the unique
         identifier validity value would be a 32-bit
         representation of the creation date/time of the mailbox.
         It is alright to use a constant such as 1, but only if
         it guaranteed that unique identifers will never be
         reused, even in the case of a mailbox being deleted and
         a new mailbox by the same name created at some future
         time.
    Message set ranges are permitted; however, there is no guarantee
    that unique identifiers be contiguous.  A non-existent unique
    identifier within a message set range is ignored without any error
    message generated.
    The number after the "*" in an untagged FETCH response is always a
    message sequence number, not a unique identifier, even for a UID
    command response.  However, server implementations MUST implicitly
    include the UID message data item as part of any FETCH response
    caused by a UID command, regardless of whether UID was specified
    as a message data item to the FETCH.

Crispin [Page 36] RFC 1730 IMAP4 December 1994

 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

6.5. Client Commands - Experimental/Expansion

6.5.1. 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: a441 CAPABILITY
             S: * CAPABILITY IMAP4 XPIG-LATIN
             S: a441 OK CAPABILITY completed
             C: A442 XPIG-LATIN
             S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
             S: A442 OK XPIG-LATIN ompleted-cay

Crispin [Page 37] RFC 1730 IMAP4 December 1994

7. Server Responses

 Server responses are in three forms: status responses, server data,
 and command continuation request.
 Server response data, identified by "Data:" in the response
 descriptions below, are described by function, not by syntax.  The
 precise syntax of server response data is described in the Formal
 Syntax section.
 The client MUST be prepared to accept any response at all times.
 Status responses that are tagged indicate the completion result of a
 client command, and have a tag matching the command.
 Some status responses, and all server data, are untagged.  An
 untagged response is indicated by the token "*" instead of a tag.
 Untagged status responses indicate server greeting, or server status
 that does not indicate the completion of a command.  For historical
 reasons, untagged server data responses are also called "unsolicited
 data", although strictly speaking only unilateral server data is
 truly "unsolicited".
 Certain server data MUST be recorded by the client when it is
 received; this is noted in the description of that data.  Such data
 conveys critical information which affects the interpretation of all
 subsequent commands and responses (e.g. updates reflecting the
 creation or destruction of messags).
 Other server data SHOULD be recorded for later reference; if the
 client does not need to record the data, or if recording the data has
 no obvious purpose (e.g. a SEARCH response when no SEARCH command is
 in progress), the data SHOULD be ignored.
 An example of unilateral untagged 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.

Crispin [Page 38] RFC 1730 IMAP4 December 1994

7.1. Server Responses - Status Responses

 Status responses may include an optional response code.  A response
 code consists of data inside square brackets in the form of an atom,
 possibly followed by a space and arguments.  The response code
 contains additional information or status codes for client software
 beyond the OK/NO/BAD condition, and are defined when there is a
 specific action that a client can take based upon the additional
 information.
 The currently defined response codes are:
    ALERT          The human-readable text contains a special alert
                   that MUST be presented to the user in a fashion
                   that calls the user's attention to the message.
    PARSE          The human-readable text represents an error in
                   parsing the [RFC-822] or [MIME-1] headers of a
                   message in the mailbox.
    PERMANENTFLAGS Followed by a parenthesized 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.

Crispin [Page 39] RFC 1730 IMAP4 December 1994

    UIDVALIDITY    Followed by a decimal number, indicates the unique
                   identifier validity value.  See the description of
                   the UID command for more detail.
    UNSEEN         Followed by a decimal number, indicates the number
                   of the first message without the \Seen flag set.
    Additional response codes defined by particular client or server
    implementations should be prefixed with an "X" until they are
    added to a revision of this protocol.  Client implementations
    should ignore response codes that they do not recognize.

7.1.1. OK Response

 Data:       optional response code
             human-readable text
    The OK response indicates an information message from the server.
    When tagged, it indicates successful completion of the associated
    command.  The human-readable text may be presented to the user as
    an information message.  The untagged form indicates an
    information-only message; the nature of the information may be
    indicated by a response code.
    The untagged form is also used as one of three possible greetings
    at 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

7.1.2. NO Response

 Data:       optional response code
             human-readable text
    The NO response indicates an operational error message from the
    server.  When tagged, it indicates unsuccessful completion of the
    associated command.  The untagged form indicates a warning; the
    command may still complete successfully.  The human-readable text
    describes the condition.

Crispin [Page 40] RFC 1730 IMAP4 December 1994

 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

7.1.3. BAD Response

 Data:       optional response code
             human-readable text
    The BAD response indicates an error message from the server.  When
    tagged, it reports a protocol-level error in the client's command;
    the tag indicates the command that caused the error.  The untagged
    form indicates a protocol-level error for which the associated
    command can not be determined; it may also indicate an internal
    server failure.  The human-readable text describes the condition.
 Example:    C: ...very long command line...
             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

7.1.4. PREAUTH Response

 Data:       optional response code
             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

Crispin [Page 41] RFC 1730 IMAP4 December 1994

7.1.5. BYE Response

 Data:       optional response code
             human-readable text
    The BYE response is always untagged, and indicates that the server
    is about to close the connection.  The human-readable text may be
    displayed to the user in a status report by the client.  The BYE
    response 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

7.2. 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.

7.2.1. 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".
    A capability name other than IMAP4 indicates that the server
    supports an extension, revision, or amendment to the IMAP4
    protocol.  Server responses MUST conform to this document until
    the client issues a command that uses the associated capability.
    Capability names MUST either begin with "X" or be standard or
    standards-track IMAP4 extensions, revisions, or amendments
    registered with IANA.  A server MUST NOT offer unregistered or
    non-standard capability names, unless such names are prefixed with
    an "X".

Crispin [Page 42] RFC 1730 IMAP4 December 1994

    Client implementations SHOULD NOT require any capability name
    other than "IMAP4", and MUST ignore any unknown capability names.
 Example:    S: * CAPABILITY IMAP4 XPIG-LATIN

7.2.2. 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
                   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, or if the name is a \Noselect
    name, the server 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.

Crispin [Page 43] RFC 1730 IMAP4 December 1994

    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

7.2.3. 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

7.2.4. 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

7.2.5. FLAGS Response

 Data:       flag parenthesized list
    The FLAGS response occurs as a result of a SELECT or EXAMINE
    command.  The flag parenthesized list identifies the flags (at a
    minimum, the system-defined flags) that are applicable for this
    mailbox.  Flags other than the system flags may also exist,
    depending on server implementation.
    The update from the FLAGS response MUST be recorded by the client.
 Example:    S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)

Crispin [Page 44] RFC 1730 IMAP4 December 1994

7.3. 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.

7.3.1. 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).
    The update from the EXISTS response MUST be recorded by the
    client.
 Example:    S: * 23 EXISTS

7.3.2. 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).
    The update from the RECENT response MUST be recorded by the
    client.
 Example:    S: * 5 RECENT

7.3.3. EXPUNGE Response

 Data:       none
    The EXPUNGE response reports that the specified message sequence
    number has been permanently removed from the mailbox.  The message
    sequence number for each successive message in the mailbox is
    immediately decremented by 1, and this decrement is reflected in
    message sequence numbers in subsequent responses (including other
    untagged EXPUNGE responses).

Crispin [Page 45] RFC 1730 IMAP4 December 1994

    As a result of the immediate decrement rule, message sequence
    numbers that appear in a set of successive EXPUNGE responses
    depend upon whether the messages are removed starting from lower
    numbers to higher numbers, or from higher numbers to lower
    numbers.  For example, if the last 5 messages in a 9-message
    mailbox are expunged; a "lower to higher" server will send five
    untagged EXPUNGE responses for message sequence number 5, whereas
    a "higher to lower server" will send successive untagged EXPUNGE
    responses for message sequence numbers 9, 8, 7, 6, and 5.
    An EXPUNGE response MUST NOT be sent when no command is in
    progress; nor while responding to a FETCH, STORE, or SEARCH
    command.  This rule is necessary to prevent a loss of
    synchronization of message sequence numbers between client and
    server.
    The update from the EXPUNGE response MUST be recorded by the
    client.
 Example:    S: * 44 EXPUNGE

7.3.4. 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
    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
                   parenthesized 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

Crispin [Page 46] RFC 1730 IMAP4 December 1994

                   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 parenthesized list there is a nested
                   body.  The second element of the parenthesized 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 parenthesized 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-1].
                   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 parenthesized 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-1].

Crispin [Page 47] RFC 1730 IMAP4 December 1994

                   body subtype
                      A string giving the content subtype name as
                      defined in [MIME-1].
                   body parameter parenthesized 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-1].
                   body id
                      A string giving the content id as defined in
                      [MIME-1].
                   body description
                      A string giving the content description as
                      defined in [MIME-1].
                   body encoding
                      A string giving the content transfer encoding as
                      defined in [MIME-1].
                   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
                   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:

Crispin [Page 48] RFC 1730 IMAP4 December 1994

                   body MD5
                      A string giving the content MD5 value as defined
                      in [MIME-1].
                   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] 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, 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.

Crispin [Page 49] RFC 1730 IMAP4 December 1994

    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].
    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-1] 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
                   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.

Crispin [Page 50] RFC 1730 IMAP4 December 1994

    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-1] 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)

7.3.5. Obsolete Responses

 In addition to the responses listed in here, client implementations
 MUST accept and implement the obsolete responses described in
 Appendix B.

7.4. 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 octets 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.  The
 remainder of the command, including the CRLF that terminates a
 command, follows the octets of the literal.  If there are any
 additional command arguments the literal octets are followed by a
 space and those arguments.
 Example:    C: A001 LOGIN {11}
             S: + Ready for additional command text
             C: FRED FOOBAR {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"

Crispin [Page 51] RFC 1730 IMAP4 December 1994

8. 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:   * OK [UIDVALIDITY 3857529045] UIDs valid
 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

Crispin [Page 52] RFC 1730 IMAP4 December 1994

9. 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" / "K" / "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" / "k" / "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

Crispin [Page 53] RFC 1730 IMAP4 December 1994

 atom            ::= 1*ATOM_CHAR
 ATOM_CHAR       ::= <any CHAR except atom_specials>
 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

Crispin [Page 54] RFC 1730 IMAP4 December 1994

 body_fld_md5    ::= nstring
 body_fld_octets ::= number
 body_fld_param  ::= "(" 1#(string string) ")" / nil
 body_fld_subtyp ::= string
 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
 capability_data ::= "CAPABILITY" SPACE "IMAP4" [SPACE 1#capability]
 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 in Authenticated or Selected state

Crispin [Page 55] RFC 1730 IMAP4 December 1994

 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 set SPACE mailbox
 CR              ::= <ASCII CR, carriage return, 0x0C>
 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

Crispin [Page 56] RFC 1730 IMAP4 December 1994

 delete          ::= "DELETE" SPACE mailbox
                     ;; Use of INBOX gives a NO error
 digit           ::= "0" / digit_nz
 digit_nz        ::= "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
 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 set 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

Crispin [Page 57] RFC 1730 IMAP4 December 1994

 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
 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 *CHAR8
                     ;; 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#nz_number] /
                      number SPACE "EXISTS" / number SPACE "RECENT"

Crispin [Page 58] RFC 1730 IMAP4 December 1994

 mailbox_list    ::= "(" #("\Marked" / "\Noinferiors" /
                     "\Noselect" / "\Unmarked" / flag_extension) ")"
                     SPACE (<"> QUOTED_CHAR <"> / nil) SPACE mailbox
 message_data    ::= nz_number SPACE ("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
                     ;; Unsigned 32-bit integer
                     ;; (0 <= n < 4,294,967,296)
 nz_number       ::= digit_nz *digit
                     ;; Non-zero unsigned 32-bit integer
                     ;; (0 < n < 4,294,967,296)
 partial         ::= "PARTIAL" SPACE nz_number SPACE
                     ("BODY" [".PEEK"] "[" section "]" /
                     "RFC822" (([".TEXT"] [".PEEK"]) / ".HEADER")
                     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

Crispin [Page 59] RFC 1730 IMAP4 December 1994

 response        ::= *response_data response_done
 response_data   ::= "*" SPACE (resp_cond_state / resp_cond_bye /
                     mailbox_data / message_data / capability_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_text_code "]" SPACE] (text_mime2 / text)
 resp_text_code  ::= "ALERT" / "PARSE" /
                     "PERMANENTFLAGS" SPACE "(" #(flag / "\*") ")" /
                     "READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
                     "UIDVALIDITY" SPACE nz_number /
                     "UNSEEN" SPACE nz_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
 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 set / "UNDRAFT" / set /
                     "(" search_criteria ")"
                     ;; New in IMAP4

Crispin [Page 60] RFC 1730 IMAP4 December 1994

 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 [IMAP2]
 section         ::= "0" / nz_number ["." section]
 select          ::= "SELECT" SPACE mailbox
 sequence_num    ::= nz_number / "*"
                     ;; * is the largest number in use.  For message
                     ;; sequence 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.
 set             ::= sequence_num / (sequence_num ":" sequence_num) /
                     (set "," set)
                     ;; Identifies a set of messages.  For message
                     ;; sequence 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.
 SPACE           ::= <ASCII SP, space, 0x20>
 store           ::= "STORE" SPACE set SPACE store_att_flags
 store_att_flags ::= (["+" / "-"] "FLAGS" [".SILENT"]) SPACE
                     (flag_list / #flag)
 string          ::= quoted / literal
 subscribe       ::= ("SUBSCRIBE" SPACE mailbox) / subscribe_obs
 subscribe_obs   ::= "SUBSCRIBE" SPACE "MAILBOX" SPACE mailbox
                     ;;OBSOLETE

Crispin [Page 61] RFC 1730 IMAP4 December 1994

 tag             ::= 1*<any ATOM_CHAR except "+">
 text            ::= 1*TEXT_CHAR
 text_mime2       ::= "=?" <charset> "?" <encoding> "?"
                      <encoded-text> "?="
                      ;; Syntax defined in [MIME-2]
 TEXT_CHAR       ::= <any CHAR except CR and LF>
 time            ::= 2digit ":" 2digit ":" 2digit
                     ;; Hours minutes seconds
 uid             ::= "UID" SPACE (copy / fetch / search / store)
                     ;; Unique identifiers used instead of message
                     ;; sequence numbers
 uniqueid        ::= nz_number
                     ;; Strictly ascending
 unsubscribe     ::= ("UNSUBSCRIBE" SPACE mailbox) / unsubscribe_obs
 unsubscribe_obs ::= "UNSUBSCRIBE" SPACE "MAILBOX" SPACE mailbox
                     ;;OBSOLETE
 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".

Crispin [Page 62] RFC 1730 IMAP4 December 1994

 zone_old        ::= "UT" / "GMT" / "Z" /                ;; +0000
                     "AST" / "EDT" /                     ;; -0400
                     "EST" / "CDT" /                     ;; -0500
                     "CST" / "MDT" /                     ;; -0600
                     "MST" / "PDT" /                     ;; -0700
                     "PST" / "YDT" /                     ;; -0800
                     "YST" / "HDT" /                     ;; -0900
                     "HST" / "BDT" /                     ;; -1000
                     "BST" /                             ;; -1100
                     "A" / "B" / "C" / "D" / "E" / "F" / ;; +1 to +6
                     "G" / "H" / "I" / "K" / "L" / "M" / ;; +7 to +12
                     "N" / "O" / "P" / "Q" / "R" / "S" / ;; -1 to -6
                     "T" / "U" / "V" / "W" / "X" / "Y"   ;; -7 to -12
                     ;; OBSOLETE

Crispin [Page 63] RFC 1730 IMAP4 December 1994

10. Author's Note

 This document is a revision or rewrite of earlier documents, and
 supercedes the protocol specification in those documents: IMAP4
 Internet drafts, the IMAP2bis Internet drafts, unpublished
 IMAP2bis.TXT document, RFC 1176, and RFC 1064.

11. 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.

12. 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

Crispin [Page 64] RFC 1730 IMAP4 December 1994

Appendices

A. Obsolete Commands

 The following commands are OBSOLETE.  It is NOT required to support
 any of these commands in new server implementations.  These commands
 are documented here for the benefit of implementors who may wish to
 support them for compatibility with old client implementations.
 The section headings of these commands are intended to correspond
 with where they would be located in the main document if they were
 not obsoleted.

A.6.3.OBS.1. 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
    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

A.6.3.OBS.2. 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
    The FIND MAILBOXES command returns a subset of names from the set
    of names that the user has declared as being "active" or

Crispin [Page 65] RFC 1730 IMAP4 December 1994

    "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 "?"
    match a single character.
 Example:    C: A002 FIND MAILBOXES *
             S: * MAILBOX blurdybloop
             S: * MAILBOX INBOX
             S: A002 OK FIND MAILBOXES completed

A.6.3.OBS.3. SUBSCRIBE MAILBOX Command

 Arguments:  mailbox name
 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 MAILBOX command is identical in effect to the
    SUBSCRIBE command.  A server which implements this command must be
    able to distinguish between a SUBSCRIBE MAILBOX command and a
    SUBSCRIBE command with a mailbox name argument of "MAILBOX".
 Example:    C: A002 SUBSCRIBE MAILBOX #news.comp.mail.mime
             S: A002 OK SUBSCRIBE MAILBOX to #news.comp.mail.mime
             completed
             C: A003 SUBSCRIBE MAILBOX
             S: A003 OK SUBSCRIBE to MAILBOX completed

A.6.3.OBS.4. UNSUBSCRIBE MAILBOX 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 MAILBOX command is identical in effect to the
    UNSUBSCRIBE command.  A server which implements this command must
    be able to distinguish between a UNSUBSCRIBE MAILBOX command and
    an UNSUBSCRIBE command with a mailbox name argument of "MAILBOX".

Crispin [Page 66] RFC 1730 IMAP4 December 1994

 Example:    C: A002 UNSUBSCRIBE MAILBOX #news.comp.mail.mime
             S: A002 OK UNSUBSCRIBE MAILBOX from #news.comp.mail.mime
             completed
             C: A003 UNSUBSCRIBE MAILBOX
             S: A003 OK UNSUBSCRIBE from MAILBOX completed

Crispin [Page 67] RFC 1730 IMAP4 December 1994

B. Obsolete Responses

 The following responses are OBSOLETE.  Except as noted below, these
 responses MUST NOT be transmitted by new server implementations.
 The section headings of these responses are intended to correspond
 with where they would be located in the main document if they were
 not obsoleted.

B.7.2.OBS.1. MAILBOX Response

 Data:       name
    The MAILBOX response MUST NOT be transmitted by server
    implementations except in response to the obsolete FIND MAILBOXES
    and FIND ALL.MAILBOXES commands.  Client implementations that do
    not use these commands MAY ignore this response.  It is documented
    here for the benefit of implementors who may wish to support it
    for 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

B.7.3.OBS.1. COPY Response

 Data:       none
    The COPY response MUST NOT be transmitted by new server
    implementations.  Client implementations MUST ignore the COPY
    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

Crispin [Page 68] RFC 1730 IMAP4 December 1994

B.7.3.OBS.2. STORE Response

 Data:       message data
    The STORE response MUST NOT be transmitted by new server
    implementations.  Client implementations MUST treat the STORE
    response as equivalent to the FETCH 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 instead of FETCH in response to a STORE command to report
    the new value of the flags.
 Example:    S: * 69 STORE (FLAGS (\Deleted))

Crispin [Page 69] RFC 1730 IMAP4 December 1994

C. References

 [IMAP-AUTH] Myers, J., "IMAP4 Authentication Mechanism", RFC 1731.
 Carnegie-Mellon University, December 1994.
 [IMAP-COMPAT] Crispin, M. "IMAP4 Compatibility with IMAP2 and
 IMAP2bis", RFC 1732, University of Washington, December 1994.
 [IMAP-DISC] Austein, R. "Synchronization Operations for Disconnected
 IMAP4 Clients", Work in Progress.
 [IMAP-MODEL] Crispin, M. "Distributed Electronic Mail Models in
 IMAP4", RFC 1733, University of Washington, December 1994.
 [IMAP-NAMING] Crispin, M. "Mailbox Naming Convention in IMAP4", Work
 in Progress.
 [IMAP2] Crispin, M., "Interactive Mail Access Protocol - Version 2",
 RFC 1176, University of Washington, August 1990.
 [IMSP] Myers, J. "IMSP -- Internet Message Support Protocol", Work in
 Progress.
 [MIME-1] Borenstein, N., and Freed, N., "MIME (Multipurpose Internet
 Mail Extensions) Part One: Mechanisms for Specifying and Describing
 the Format of Internet Message Bodies", RFC 1521, Bellcore, Innosoft,
 September 1993.
 [MIME-2] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
 Part Two: Message Header Extensions for Non-ASCII Text", RFC 1522,
 University of Tennessee, September 1993.
 [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
 Messages", STD 11, RFC 822, University of Delaware, August 1982.
 [SMTP] Postel, Jonathan B. "Simple Mail Transfer Protocol", STD 10,
 RFC 821, USC/Information Sciences Institute, August 1982.

Crispin [Page 70] RFC 1730 IMAP4 December 1994

E. IMAP4 Keyword Index

     +FLAGS <flag list> (store command data item) ...............   34
     +FLAGS.SILENT <flag list> (store command data item) ........   34
     -FLAGS <flag list> (store command data item) ...............   34
     -FLAGS.SILENT <flag list> (store command data item) ........   34
     ALERT (response code) ......................................   39
     ALL (fetch item) ...........................................   29
     ALL (search key) ...........................................   27
     ANSWERED (search key) ......................................   27
     APPEND (command) ...........................................   22
     AUTHENTICATE (command) .....................................   12
     BAD (response) .............................................   41
     BCC <string> (search key) ..................................   27
     BEFORE <date> (search key) .................................   27
     BODY (fetch item) ..........................................   29
     BODY (fetch result) ........................................   46
     BODY <string> (search key) .................................   27
     BODY.PEEK[<section>] (fetch item) ..........................   30
     BODYSTRUCTURE (fetch item) .................................   31
     BODYSTRUCTURE (fetch result) ...............................   47
     BODY[<section>] (fetch item) ...............................   29
     BODY[section] (fetch result) ...............................   46
     BYE (response) .............................................   41
     CAPABILITY (command) .......................................   10
     CAPABILITY (response) ......................................   42
     CC <string> (search key) ...................................   27
     CHECK (command) ............................................   23
     CLOSE (command) ............................................   24
     COPY (command) .............................................   34
     COPY (response) ............................................   68
     CREATE (command) ...........................................   17
     DELETE (command) ...........................................   18
     DELETED (search key) .......................................   27
     DRAFT (search key) .........................................   27
     ENVELOPE (fetch item) ......................................   31
     ENVELOPE (fetch result) ....................................   49
     EXAMINE (command) ..........................................   16
     EXISTS (response) ..........................................   45
     EXPUNGE (command) ..........................................   25
     EXPUNGE (response) .........................................   45
     FAST (fetch item) ..........................................   31
     FETCH (command) ............................................   29
     FETCH (response) ...........................................   46
     FIND ALL.MAILBOXES (command) ...............................   65
     FIND MAILBOXES (command) ...................................   65
     FLAGGED (search key) .......................................   27
     FLAGS (fetch item) .........................................   31

Crispin [Page 71] RFC 1730 IMAP4 December 1994

     FLAGS (fetch result) .......................................   50
     FLAGS (response) ...........................................   44
     FLAGS <flag list> (store command data item) ................   34
     FLAGS.SILENT <flag list> (store command data item) .........   34
     FROM <string> (search key) .................................   27
     FULL (fetch item) ..........................................   31
     HEADER <field-name> <string> (search key) ..................   27
     INTERNALDATE (fetch item) ..................................   31
     INTERNALDATE (fetch result) ................................   50
     KEYWORD <flag> (search key) ................................   27
     LARGER <n> (search key) ....................................   27
     LIST (command) .............................................   20
     LIST (response) ............................................   43
     LOGIN (command) ............................................   14
     LOGOUT (command) ...........................................   11
     LSUB (command) .............................................   22
     LSUB (response) ............................................   44
     MAILBOX (response) .........................................   68
     NEW (search key) ...........................................   27
     NO (response) ..............................................   40
     NOOP (command) .............................................   11
     NOT <search-key> (search key) ..............................   28
     OK (response) ..............................................   40
     OLD (search key) ...........................................   28
     ON <date> (search key) .....................................   28
     OR <search-key1> <search-key2> (search key) ................   28
     PARSE (response code) ......................................   39
     PARTIAL (command) ..........................................   32
     PERMANENTFLAGS (response code) .............................   39
     PREAUTH (response) .........................................   41
     READ-ONLY (response code) ..................................   39
     READ-WRITE (response code) .................................   39
     RECENT (response) ..........................................   45
     RECENT (search key) ........................................   28
     RENAME (command) ...........................................   18
     RFC822 (fetch item) ........................................   31
     RFC822 (fetch result) ......................................   50
     RFC822.HEADER (fetch item) .................................   31
     RFC822.HEADER (fetch result) ...............................   50
     RFC822.HEADER.LINES <header_list> (fetch item) .............   31
     RFC822.HEADER.LINES.NOT <header_list> (fetch item) .........   32
     RFC822.PEEK (fetch item) ...................................   31
     RFC822.SIZE (fetch item) ...................................   32
     RFC822.SIZE (fetch result) .................................   50
     RFC822.TEXT (fetch item) ...................................   32
     RFC822.TEXT (fetch result) .................................   51
     RFC822.TEXT.PEEK (fetch item) ..............................   32
     SEARCH (command) ...........................................   25

Crispin [Page 72] RFC 1730 IMAP4 December 1994

     SEARCH (response) ..........................................   44
     SEEN (search key) ..........................................   28
     SELECT (command) ...........................................   15
     SENTBEFORE <date> (search key) .............................   28
     SENTON <date> (search key) .................................   28
     SENTSINCE <date> (search key) ..............................   28
     SINCE <date> (search key) ..................................   28
     SMALLER <n> (search key) ...................................   28
     STORE (command) ............................................   33
     STORE (response) ...........................................   69
     SUBJECT <string> (search key) ..............................   28
     SUBSCRIBE (command) ........................................   19
     SUBSCRIBE MAILBOX (command) ................................   66
     TEXT <string> (search key) .................................   28
     TO <string> (search key) ...................................   28
     TRYCREATE (response code) ..................................   39
     UID (command) ..............................................   35
     UID (fetch item) ...........................................   32
     UID (fetch result) .........................................   51
     UID <message set> (search key) .............................   28
     UIDVALIDITY (response code) ................................   40
     UNANSWERED (search key) ....................................   29
     UNDELETED (search key) .....................................   29
     UNDRAFT (search key) .......................................   29
     UNFLAGGED (search key) .....................................   29
     UNKEYWORD <flag> (search key) ..............................   29
     UNSEEN (response code) .....................................   40
     UNSEEN (search key) ........................................   29
     UNSUBSCRIBE (command) ......................................   19
     UNSUBSCRIBE MAILBOX (command) ..............................   66
     X<atom> (command) ..........................................   37
     \Answered (system flag) ....................................   50
     \Deleted (system flag) .....................................   50
     \Draft (system flag) .......................................   50
     \Flagged (system flag) .....................................   50
     \Marked (mailbox name attribute) ...........................   43
     \Noinferiors (mailbox name attribute) ......................   43
     \Noselect (mailbox name attribute) .........................   43
     \Recent (system flag) ......................................   50
     \Seen (system flag) ........................................   50
     \Unmarked (mailbox name attribute) .........................   43

Crispin [Page 73]

/data/webs/external/dokuwiki/data/pages/rfc/rfc1730.txt · Last modified: 1994/12/19 23:04 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki