bincimap

rfc2060.txt (182481B)

---

 
 
 
 
 
 
 Network Working Group                                        M. Crispin
 Request for Comments: 2060                     University of Washington
 Obsoletes: 1730                                           December 1996
 Category: Standards Track
 
 
             INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
 
 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 4rev1 (IMAP4rev1)
    allows a client to access and manipulate electronic mail messages on
    a server.  IMAP4rev1 permits manipulation of remote message folders,
    called "mailboxes", in a way that is functionally equivalent to local
    mailboxes.  IMAP4rev1 also provides the capability for an offline
    client to resynchronize with the server (see also [IMAP-DISC]).
 
    IMAP4rev1 includes operations for creating, deleting, and renaming
    mailboxes; checking for new messages; permanently removing messages;
    setting and clearing flags; [RFC-822] and [MIME-IMB] parsing;
    searching; and selective fetching of message attributes, texts, and
    portions thereof.  Messages in IMAP4rev1 are accessed by the use of
    numbers.  These numbers are either message sequence numbers or unique
    identifiers.
 
    IMAP4rev1 supports a single server.  A mechanism for accessing
    configuration information to support multiple IMAP4rev1 servers is
    discussed in [ACAP].
 
    IMAP4rev1 does not specify a means of posting mail; this function is
    handled by a mail transfer protocol such as [SMTP].
 
    IMAP4rev1 is designed to be upwards compatible from the [IMAP2] and
    unpublished IMAP2bis protocols.  In the course of the evolution of
    IMAP4rev1, some aspects in the earlier protocol have become obsolete.
    Obsolete commands, responses, and data formats which an IMAP4rev1
    implementation may encounter when used with an earlier implementation
    are described in [IMAP-OBSOLETE].
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
    Other compatibility issues with IMAP2bis, the most common variant of
    the earlier protocol, are discussed in [IMAP-COMPAT].  A full
    discussion of compatibility issues with rare (and presumed extinct)
    variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is
    primarily of historical interest.
 
 Table of Contents
 
 IMAP4rev1 Protocol Specification ..................................    4
 1.      How to Read This Document .................................    4
 1.1.    Organization of This Document .............................    4
 1.2.    Conventions Used in This Document .........................    4
 2.      Protocol Overview .........................................    5
 2.1.    Link Level ................................................    5
 2.2.    Commands and Responses ....................................    6
 2.2.1.  Client Protocol Sender and Server Protocol Receiver .......    6
 2.2.2.  Server Protocol Sender and Client Protocol Receiver .......    7
 2.3.    Message Attributes ........................................    7
 2.3.1.  Message Numbers ...........................................    7
 2.3.1.1.        Unique Identifier (UID) Message Attribute .........    7
 2.3.1.2.        Message Sequence Number Message Attribute .........    9
 2.3.2.  Flags Message Attribute ....................................   9
 2.3.3.  Internal Date Message Attribute ...........................   10
 2.3.4.  [RFC-822] Size Message Attribute ..........................   11
 2.3.5.  Envelope Structure Message Attribute ......................   11
 2.3.6.  Body Structure Message Attribute ..........................   11
 2.4.    Message Texts .............................................   11
 3.      State and Flow Diagram ....................................   11
 3.1.    Non-Authenticated State ...................................   11
 3.2.    Authenticated State .......................................   11
 3.3.    Selected State ............................................   12
 3.4.    Logout State ..............................................   12
 4.      Data Formats ..............................................   12
 4.1.    Atom ......................................................   13
 4.2.    Number ....................................................   13
 4.3.    String .....................................................  13
 4.3.1.  8-bit and Binary Strings ..................................   13
 4.4.    Parenthesized List ........................................   14
 4.5.    NIL .......................................................   14
 5.      Operational Considerations ................................   14
 5.1.    Mailbox Naming ............................................   14
 5.1.1.  Mailbox Hierarchy Naming ..................................   14
 5.1.2.  Mailbox Namespace Naming Convention .......................   14
 5.1.3.  Mailbox International Naming Convention ...................   15
 5.2.    Mailbox Size and Message Status Updates ...................   16
 5.3.    Response when no Command in Progress ......................   16
 5.4.    Autologout Timer ..........................................   16
 5.5.    Multiple Commands in Progress .............................   17
 
 
 
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 6.      Client Commands ...........................................   17
 6.1.    Client Commands - Any State ...............................   18
 6.1.1.  CAPABILITY Command ........................................   18
 6.1.2.  NOOP Command ..............................................   19
 6.1.3.  LOGOUT Command ............................................   20
 6.2.    Client Commands - Non-Authenticated State .................   20
 6.2.1.  AUTHENTICATE Command ......................................   21
 6.2.2.  LOGIN Command .............................................   22
 6.3.    Client Commands - Authenticated State .....................   22
 6.3.1.  SELECT Command ............................................   23
 6.3.2.  EXAMINE Command ...........................................   24
 6.3.3.  CREATE Command ............................................   25
 6.3.4.  DELETE Command ............................................   26
 6.3.5.  RENAME Command ............................................   27
 6.3.6.  SUBSCRIBE Command .........................................   29
 6.3.7.  UNSUBSCRIBE Command .......................................   30
 6.3.8.  LIST Command ..............................................   30
 6.3.9.  LSUB Command ..............................................   32
 6.3.10. STATUS Command ............................................   33
 6.3.11. APPEND Command ............................................   34
 6.4.    Client Commands - Selected State ..........................   35
 6.4.1.  CHECK Command .............................................   36
 6.4.2.  CLOSE Command .............................................   36
 6.4.3.  EXPUNGE Command ...........................................   37
 6.4.4.  SEARCH Command ............................................   37
 6.4.5.  FETCH Command .............................................   41
 6.4.6.  STORE Command .............................................   45
 6.4.7.  COPY Command ..............................................   46
 6.4.8.  UID Command ...............................................   47
 6.5.    Client Commands - Experimental/Expansion ..................   48
 6.5.1.  X<atom> Command ...........................................   48
 7.      Server Responses ..........................................   48
 7.1.    Server Responses - Status Responses .......................   49
 7.1.1.  OK Response ...............................................   51
 7.1.2.  NO Response ...............................................   51
 7.1.3.  BAD Response ..............................................   52
 7.1.4.  PREAUTH Response ..........................................   52
 7.1.5.  BYE Response ..............................................   52
 7.2.    Server Responses - Server and Mailbox Status ..............   53
 7.2.1.  CAPABILITY Response .......................................   53
 7.2.2.  LIST Response ..............................................  54
 7.2.3.  LSUB Response .............................................   55
 7.2.4   STATUS Response ...........................................   55
 7.2.5.  SEARCH Response ...........................................   55
 7.2.6.  FLAGS Response ............................................   56
 7.3.    Server Responses - Mailbox Size ...........................   56
 7.3.1.  EXISTS Response ...........................................   56
 7.3.2.  RECENT Response ...........................................   57
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 7.4.    Server Responses - Message Status .........................   57
 7.4.1.  EXPUNGE Response ..........................................   57
 7.4.2.  FETCH Response ............................................   58
 7.5.    Server Responses - Command Continuation Request ...........   63
 8.      Sample IMAP4rev1 connection ...............................   63
 9.      Formal Syntax .............................................   64
 10.     Author's Note .............................................   74
 11.     Security Considerations ...................................   74
 12.     Author's Address ..........................................   75
 Appendices ........................................................   76
 A.      References ................................................   76
 B.      Changes from RFC 1730 .....................................   77
 C.      Key Word Index ............................................   79
 
 
 IMAP4rev1 Protocol Specification
 
 1.      How to Read This Document
 
 1.1.    Organization of This Document
 
    This document is written from the point of view of the implementor of
    an IMAP4rev1 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 IMAP4rev1
    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, do not attempt to deduce command syntax from the command
    section alone; 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.
 
    The following terms are used in this document to signify the
    requirements of this specification.
 
    1) MUST, or the adjective REQUIRED, means that the definition is
       an absolute requirement of the specification.
 
    2) MUST NOT that the definition is an absolute prohibition of the
       specification.
 
 
 
 
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    3) SHOULD means that there may exist valid reasons in particular
       circumstances to ignore a particular item, but the full
       implications MUST be understood and carefully weighed before
       choosing a different course.
 
    4) SHOULD NOT means that there may exist valid reasons in
       particular circumstances when the particular behavior is
       acceptable or even useful, but the full implications SHOULD be
       understood and the case carefully weighed before implementing
       any behavior described with this label.
 
    5) MAY, or the adjective OPTIONAL, means that an item is truly
       optional.  One vendor may choose to include the item because a
       particular marketplace requires it or because the vendor feels
       that it enhances the product while another vendor may omit the
       same item.  An implementation which does not include a
       particular option MUST be prepared to interoperate with another
       implementation which does include the option.
 
       "Can" is used instead of "may" when referring to a possible
       circumstance or situation, as opposed to an optional facility of
       the protocol.
 
       "User" is used to refer to a human user, whereas "client" refers
       to the software being run by the user.
 
       "Connection" refers to the entire sequence of client/server
       interaction from the initial establishment of the network
       connection until its termination.  "Session" refers to the
       sequence of client/server interaction from the time that a mailbox
       is selected (SELECT or EXAMINE command) until the time that
       selection ends (SELECT or EXAMINE of another mailbox, CLOSE
       command, or connection termination).
 
        Characters are 7-bit US-ASCII unless otherwise specified.  Other
        character sets are indicated using a "CHARSET", as described in
        [MIME-IMT] and defined in [CHARSET].  CHARSETs have important
        additional semantics in addition to defining character set; refer
        to these documents for more detail.
 
 2.      Protocol Overview
 
 2.1.    Link Level
 
    The IMAP4rev1 protocol assumes a reliable data stream such as
    provided by TCP.  When TCP is used, an IMAP4rev1 server listens on
    port 143.
 
 
 
 
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 2.2.    Commands and Responses
 
    An IMAP4rev1 connection consists of the establishment of a
    client/server network 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 IMAP4rev1 client or server is either reading a line, or is
    reading a sequence of octets with a known count followed by a line.
 
 2.2.1.  Client Protocol Sender and Server Protocol Receiver
 
    The client command begins an operation.  Each client command is
    prefixed with an identifier (typically a short alphanumeric string,
    e.g. A0001, A0002, etc.) called a "tag".  A different tag is
    generated by the client for each command.
 
    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.  In all
       cases, the client MUST send a complete command (including
       receiving all command continuation request responses and command
       continuations for the command) before initiating a new command.
 
    The protocol receiver of an IMAP4rev1 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.
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 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
    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 IMAP4rev1 client reads a response line
    from the server.  It then takes action on the response based upon the
    first token of the response, which can be a tag, a "*", or a "+".
 
    A client MUST be prepared to accept any server response at all times.
    This includes server data that was not requested.  Server data SHOULD
    be recorded, so that the client can reference its recorded copy
    rather than sending a command to the server to request the data.  In
    the case of certain server data, the data MUST be recorded.
 
    This topic is discussed in greater detail in the Server Responses
    section.
 
 2.3.    Message Attributes
 
    In addition to message text, each message has several attributes
    associated with it.  These attributes may be retrieved individually
    or in conjunction with other attributes or message texts.
 
 2.3.1.  Message Numbers
 
    Messages in IMAP4rev1 are accessed by one of two numbers; the unique
    identifier and the message sequence number.
 
 2.3.1.1.        Unique Identifier (UID) Message Attribute
 
    A 32-bit value assigned to each message, which when used with the
    unique identifier validity value (see below) forms a 64-bit value
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
    that is permanently guaranteed not to refer to any other message in
    the mailbox.  Unique identifiers are assigned in a strictly ascending
    fashion in the mailbox; as each message is added to the mailbox it is
    assigned a higher UID than the message(s) which were added
    previously.
 
    Unlike message sequence numbers, unique identifiers are not
    necessarily contiguous.  Unique identifiers also 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 mailbox selection time.  If unique identifiers from an
    earlier session fail to persist to this session, the unique
    identifier validity value MUST be greater than the one used in the
    earlier session.
 
       Note: Unique identifiers MUST be strictly ascending in the mailbox
       at all times.  If the physical message store is re-ordered by a
       non-IMAP agent, this requires that the unique identifiers in the
       mailbox be regenerated, since the former unique identifers are no
       longer strictly ascending as a result of the re-ordering.  Another
       instance in which unique identifiers are regenerated is if the
       message store has no mechanism to store unique identifiers.
       Although this specification recognizes that this may be
       unavoidable in certain server environments, it STRONGLY ENCOURAGES
       message store implementation techniques that avoid this problem.
 
       Another cause of non-persistance is if the mailbox is deleted and
       a new mailbox with the same name is created at a later date, Since
       the name is the same, a client may not know that this is a new
       mailbox unless the unique identifier validity is different.  A
       good value to use for the unique identifier validity value is a
       32-bit representation of the creation date/time of the mailbox.
       It is alright to use a constant such as 1, but only if it
       guaranteed that unique identifiers will never be reused, even in
       the case of a mailbox being deleted (or renamed) and a new mailbox
       by the same name created at some future time.
 
    The unique identifier of a message MUST NOT change during the
    session, and SHOULD NOT change between sessions.  However, if it is
    not possible to preserve the unique identifier of a message in a
    subsequent session, each subsequent session MUST have a new unique
    identifier validity value that is larger than any that was used
    previously.
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 2.3.1.2.        Message Sequence Number Message Attribute
 
    A relative position from 1 to the number of messages in the mailbox.
    This position MUST be ordered by ascending unique identifier.  As
    each new message is added, it is assigned a message sequence number
    that is 1 higher than the number of messages in the mailbox before
    that new message was added.
 
    Message sequence numbers can be reassigned during the session.  For
    example, when a message is permanently removed (expunged) from the
    mailbox, the message sequence number for all subsequent messages is
    decremented.  Similarly, a new message can be assigned a message
    sequence number that was once held by some other message prior to an
    expunge.
 
    In addition to accessing messages by relative position in the
    mailbox, message sequence numbers can be used in mathematical
    calculations.  For example, if an untagged "EXISTS 11" is received,
    and previously an untagged "8 EXISTS" was received, three new
    messages have arrived with message sequence numbers of 9, 10, and 11.
    Another example; if message 287 in a 523 message mailbox has UID
    12345, there are exactly 286 messages which have lesser UIDs and 236
    messages which have greater UIDs.
 
 2.3.2.  Flags Message Attribute
 
    A list of zero or more named tokens associated with the message.  A
    flag is set by its addition to this list, and is cleared by its
    removal.  There are two types of flags in IMAP4rev1.  A flag of
    either type may be permanent or session-only.
 
    A system flag is a flag name that is pre-defined in this
    specification.  All system flags begin with "\".  Certain system
    flags (\Deleted and \Seen) have special semantics described
    elsewhere.  The currently-defined system flags are:
 
         \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).
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
         \Recent     Message is "recently" arrived in this mailbox.  This
                     session is the first session to have been notified
                     about this message; subsequent sessions will not see
                     \Recent set for this message.  This flag can not be
                     altered by the client.
 
                     If it is not possible to determine whether or not
                     this session is the first session to be notified
                     about a message, then that message SHOULD be
                     considered recent.
 
                     If multiple connections have the same mailbox
                     selected simultaneously, it is undefined which of
                     these connections will see newly-arrives messages
                     with \Recent set and which will see it without
                     \Recent set.
 
       A keyword is defined by the server implementation.  Keywords do
       not begin with "\".  Servers MAY permit the client to define new
       keywords in the mailbox (see the description of the
       PERMANENTFLAGS response code for more information).
 
       A flag may be permanent or session-only on a per-flag basis.
       Permanent flags are those which the client can add or remove
       from the message flags permanently; that is, subsequent sessions
       will see any change in permanent flags.  Changes to session
       flags are valid only in that session.
 
       Note: The \Recent system flag is a special case of a
       session flag.  \Recent can not be used as an argument in a
       STORE command, and thus can not be changed at all.
 
 2.3.3.  Internal Date Message Attribute
 
    The internal date and time of the message on the server.  This is not
    the date and time in the [RFC-822] header, but rather a date and time
    which reflects when the message was received.  In the case of
    messages delivered via [SMTP], this SHOULD be the date and time of
    final delivery of the message as defined by [SMTP].  In the case of
    messages delivered by the IMAP4rev1 COPY command, this SHOULD be the
    internal date and time of the source message.  In the case of
    messages delivered by the IMAP4rev1 APPEND command, this SHOULD be
    the date and time as specified in the APPEND command description.
    All other cases are implementation defined.
 
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 2.3.4.  [RFC-822] Size Message Attribute
 
    The number of octets in the message, as expressed in [RFC-822]
    format.
 
 2.3.5.  Envelope Structure Message Attribute
 
    A parsed representation of the [RFC-822] envelope information (not to
    be confused with an [SMTP] envelope) of the message.
 
 2.3.6.  Body Structure Message Attribute
 
    A parsed representation of the [MIME-IMB] body structure information
    of the message.
 
 2.4.    Message Texts
 
    In addition to being able to fetch the full [RFC-822] text of a
    message, IMAP4rev1 permits the fetching of portions of the full
    message text.  Specifically, it is possible to fetch the [RFC-822]
    message header, [RFC-822] message body, a [MIME-IMB] body part, or a
    [MIME-IMB] header.
 
 3.      State and Flow Diagram
 
    An IMAP4rev1 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 client MUST supply authentication
    credentials before most commands will be permitted.  This state is
    entered when a connection starts unless the connection has been pre-
    authenticated.
 
 3.2.    Authenticated State
 
    In authenticated state, the client is authenticated and MUST select a
    mailbox to access before commands that affect messages will be
    permitted.  This state is entered when a pre-authenticated connection
    starts, when acceptable authentication credentials have been
    provided, or after an error in selecting a mailbox.
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 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 connection 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.
 
             +--------------------------------------+
             |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
 
 4.      Data Formats
 
    IMAP4rev1 uses textual commands and responses.  Data in IMAP4rev1 can
    be in one of several forms: atom, number, string, parenthesized list,
    or NIL.
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 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 limitations of characters that can be used 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 represented as either "" (a quoted string with
    zero characters between double quotes) or as {0} followed by CRLF (a
    literal with an octet count of 0).
 
       Note: Even if the octet count is 0, a client transmitting a
       literal MUST wait to receive a command continuation request.
 
 4.3.1.  8-bit and Binary Strings
 
    8-bit textual and binary mail is supported through the use of a
    [MIME-IMB] content transfer encoding.  IMAP4rev1 implementations MAY
    transmit 8-bit or multi-octet characters in literals, but SHOULD do
    so only when the [CHARSET] is identified.
 
 
 
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
    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.
 
 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 can 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 ().
 
 5.      Operational Considerations
 
 5.1.    Mailbox Naming
 
    The interpretation of mailbox names is implementation-dependent.
    However, the case-insensitive mailbox name INBOX is a special name
    reserved to mean "the primary mailbox for this user on this server".
 
 5.1.1.  Mailbox Hierarchy Naming
 
    If it is desired to export hierarchical mailbox names, mailbox names
    MUST be left-to-right hierarchical using a single character to
    separate levels of hierarchy.  The same hierarchy separator character
    is used for all levels of hierarchy within a single name.
 
 5.1.2.  Mailbox Namespace Naming Convention
 
    By convention, the first hierarchical element of any mailbox name
    which begins with "#" identifies the "namespace" of the remainder of
    the name.  This makes it possible to disambiguate between different
    types of mailbox stores, each of which have their own namespaces.
 
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       For example, implementations which offer access to USENET
       newsgroups MAY use the "#news" namespace to partition the USENET
       newsgroup namespace from that of other mailboxes.  Thus, the
       comp.mail.misc newsgroup would have an mailbox name of
       "#news.comp.mail.misc", and the name "comp.mail.misc" could refer
       to a different object (e.g. a user's private mailbox).
 
 5.1.3.  Mailbox International Naming Convention
 
    By convention, international mailbox names are specified using a
    modified version of the UTF-7 encoding described in [UTF-7].  The
    purpose of these modifications is to correct the following problems
    with UTF-7:
 
       1) UTF-7 uses the "+" character for shifting; this conflicts with
          the common use of "+" in mailbox names, in particular USENET
          newsgroup names.
 
       2) UTF-7's encoding is BASE64 which uses the "/" character; this
          conflicts with the use of "/" as a popular hierarchy delimiter.
 
       3) UTF-7 prohibits the unencoded usage of "\"; this conflicts with
          the use of "\" as a popular hierarchy delimiter.
 
       4) UTF-7 prohibits the unencoded usage of "~"; this conflicts with
          the use of "~" in some servers as a home directory indicator.
 
       5) UTF-7 permits multiple alternate forms to represent the same
          string; in particular, printable US-ASCII chararacters can be
          represented in encoded form.
 
    In modified UTF-7, printable US-ASCII characters except for "&"
    represent themselves; that is, characters with octet values 0x20-0x25
    and 0x27-0x7e.  The character "&" (0x26) is represented by the two-
    octet sequence "&-".
 
    All other characters (octet values 0x00-0x1f, 0x7f-0xff, and all
    Unicode 16-bit octets) are represented in modified BASE64, with a
    further modification from [UTF-7] that "," is used instead of "/".
    Modified BASE64 MUST NOT be used to represent any printing US-ASCII
    character which can represent itself.
 
    "&" is used to shift to modified BASE64 and "-" to shift back to US-
    ASCII.  All names start in US-ASCII, and MUST end in US-ASCII (that
    is, a name that ends with a Unicode 16-bit octet MUST end with a "-
    ").
 
 
 
 
 
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       For example, here is a mailbox name which mixes English, Japanese,
       and Chinese text: ~peter/mail/&ZeVnLIqe-/&U,BTFw-
 
 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 detail.
 
    Regardless of what implementation decisions a client makes on
    remembering data from the server, a client implementation MUST record
    mailbox size updates.  It MUST NOT assume that any command after
    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.
 
 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.
 
 
 
 
 
 
 
 
 
 
 
 
 
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 5.5.    Multiple Commands in Progress
 
    The client MAY send another command without waiting for the
    completion result response of a command, subject to ambiguity rules
    (see below) and flow control constraints on the underlying data
    stream.  Similarly, a server MAY begin processing another command
    before processing the current command to completion, subject to
    ambiguity rules.  However, any command continuation request responses
    and command continuations MUST be negotiated before any subsequent
    command is initiated.
 
    The exception is if an ambiguity would result because of a command
    that would affect the results of other commands.  Clients MUST NOT
    send multiple commands without waiting if an ambiguity would result.
    If the server detects a possible ambiguity, it MUST execute commands
    to completion in the order given by the client.
 
    The most obvious example of ambiguity is when a command would affect
    the results of another command; for example, a FETCH of a message's
    flags and a STORE of that same message's flags.
 
    A non-obvious ambiguity occurs with commands that permit an untagged
    EXPUNGE response (commands other than FETCH, STORE, and SEARCH),
    since an untagged EXPUNGE response can invalidate sequence numbers in
    a subsequent command.  This is not a problem for FETCH, STORE, or
    SEARCH commands because servers are prohibited from sending EXPUNGE
    responses while any of those commands are in progress.  Therefore, if
    the client sends any command other than FETCH, STORE, or SEARCH, it
    MUST wait for a response before sending a command with message
    sequence numbers.
 
    For example, the following non-waiting command sequences are invalid:
 
       FETCH + NOOP + STORE
       STORE + COPY + FETCH
       COPY + COPY
       CHECK + FETCH
 
    The following are examples of valid non-waiting command sequences:
 
       FETCH + STORE + SEARCH + CHECK
       STORE + COPY + EXPUNGE
 
 6.      Client Commands
 
    IMAP4rev1 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
 
 
 
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    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 responses to be returned; these
    are identified by "Responses:" in the command descriptions below.
    See the response descriptions in the Responses section for
    information on these responses, and the Formal Syntax section for the
    precise syntax of these responses.  It is possible for server data to
    be transmitted as a result of any command; thus, commands that do not
    specifically require server data specify "no specific responses for
    this command" instead of "none".
 
    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
 
    Responses:  REQUIRED untagged response: CAPABILITY
 
    Result:     OK - capability completed
                BAD - command unknown or arguments invalid
 
       The CAPABILITY command requests a listing of capabilities that the
       server supports.  The server MUST send a single untagged
       CAPABILITY response with "IMAP4rev1" as one of the listed
       capabilities 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 connection.
 
 
 
 
 
 
 
 
 
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       A capability name which begins with "AUTH=" indicates that the
       server supports that particular authentication mechanism.  All
       such names are, by definition, part of this specification.  For
       example, the authorization capability for an experimental
       "blurdybloop" authenticator would be "AUTH=XBLURDYBLOOP" and not
       "XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".
 
       Other capability names refer to extensions, revisions, or
       amendments to this specification.  See the documentation of the
       CAPABILITY response for additional information.  No capabilities,
       beyond the base IMAP4rev1 set defined in this specification, 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 IMAP4rev1 AUTH=KERBEROS_V4
                S: abcd OK CAPABILITY completed
 
 6.1.2.  NOOP Command
 
    Arguments:  none
 
    Responses:  no specific responses 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
 
 
 
 
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 6.1.3.  LOGOUT Command
 
    Arguments:  none
 
    Responses:  REQUIRED untagged response: BYE
 
    Result:     OK - logout completed
                BAD - command unknown or arguments invalid
 
       The LOGOUT command informs the server that the client is done with
       the connection.  The server MUST send a BYE untagged response
       before the (tagged) OK response, and then close the network
       connection.
 
    Example:    C: A023 LOGOUT
                S: * BYE IMAP4rev1 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.
 
 
 
 
 
 
 
 
 
 
 
 
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 6.2.1.  AUTHENTICATE Command
 
    Arguments:  authentication mechanism name
 
    Responses:  continuation data can be requested
 
    Result:     OK - authenticate completed, now in authenticated state
                NO - authenticate failure: unsupported authentication
                     mechanism, credentials rejected
               BAD - command unknown or arguments invalid,
                     authentication exchange cancelled
 
       The AUTHENTICATE command indicates 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
       client.  It MAY also negotiate an OPTIONAL 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 issues 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 connection.  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.
 
       Authentication mechanisms are OPTIONAL.  Protection mechanisms are
       also OPTIONAL; an authentication mechanism MAY be implemented
       without any protection mechanism.  If an AUTHENTICATE command
       fails with a NO response, the client MAY try another
 
 
 
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       authentication mechanism by issuing another AUTHENTICATE command,
       or MAY attempt to authenticate by using the LOGIN command.  In
       other words, the client MAY request authentication types in
       decreasing order of preference, with the LOGIN command as a last
       resort.
 
    Example:    S: * OK KerberosV4 IMAP4rev1 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
 
    Responses:  no specific responses 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 client 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.
 
    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,
    STATUS, and APPEND.
 
 
 
 
 
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 6.3.1.  SELECT Command
 
    Arguments:  mailbox name
 
    Responses:  REQUIRED 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.  See the description
                   of the FLAGS response for more detail.
 
       <n> EXISTS  The number of messages in the mailbox.  See the
                   description of the EXISTS response for more detail.
 
       <n> RECENT  The number of messages with the \Recent flag set.
                   See the description of the RECENT response for more
                   detail.
 
       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.
 
    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 can change permanently.
 
    Only one mailbox can be selected at a time in a connection;
    simultaneous access to multiple mailboxes requires multiple
    connections.  The SELECT command automatically deselects any
    currently selected mailbox before attempting the new selection.
    Consequently, if a mailbox is selected and a SELECT command that
    fails is attempted, no mailbox is selected.
 
 
 
 
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    If the client is permitted to modify the mailbox, the server
    SHOULD prefix the text of the tagged OK response with the
          "[READ-WRITE]" response code.
 
       If the client is not permitted to modify the mailbox but is
       permitted read access, the mailbox is selected as read-only, and
       the server MUST prefix the text of the tagged OK response to
       SELECT with the "[READ-ONLY]" response code.  Read-only access
       through SELECT differs from the EXAMINE command in that certain
       read-only mailboxes MAY permit the change of permanent state on a
       per-user (as opposed to global) basis.  Netnews messages marked in
       a server-based .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
 
    Responses:  REQUIRED 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.
 
 
 
 
 
 
 
 
 
 
 
 
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       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
 
    Responses:  no specific responses 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 intends to create
       mailbox names under this name in the hierarchy.  Server
       implementations that do not require this declaration MUST ignore
       it.
 
       If the server's hierarchy separator character appears elsewhere in
       the name, the server SHOULD create any superior hierarchical names
       that are needed for the CREATE command to complete successfully.
       In other words, an attempt to create "foo/bar/zap" on a server in
       which "/" is the hierarchy separator character SHOULD create foo/
       and foo/bar/ if they do not already exist.
 
       If a new mailbox is created with the same name as a mailbox which
       was deleted, its unique identifiers MUST be greater than any
       unique identifiers used in the previous incarnation of the mailbox
       UNLESS the new incarnation has a different unique identifier
       validity value.  See the description of the UID command for more
       detail.
 
 
 
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    Example:    C: A003 CREATE owatagusiam/
                S: A003 OK CREATE completed
                C: A004 CREATE owatagusiam/blurdybloop
                S: A004 OK CREATE completed
 
       Note: the interpretation of this example depends on whether "/"
       was returned as the hierarchy separator from LIST.  If "/" is the
       hierarchy separator, a new level of hierarchy named "owatagusiam"
       with a member called "blurdybloop" is created.  Otherwise, two
       mailboxes at the same hierarchy level are created.
 
 6.3.4.  DELETE Command
 
    Arguments:  mailbox name
 
    Responses:  no specific responses for this command
 
    Result:     OK - delete completed
                NO - delete failure: can't delete mailbox with that name
                BAD - command unknown or arguments invalid
 
       The DELETE command permanently removes the mailbox with the given
       name.  A tagged OK response is returned only if the mailbox has
       been deleted.  It is an error to attempt to delete INBOX or a
       mailbox name that does not exist.
 
       The DELETE command MUST NOT remove inferior hierarchical names.
       For example, if a mailbox "foo" has an inferior "foo.bar"
       (assuming "." is the hierarchy delimiter character), removing
       "foo" MUST NOT remove "foo.bar".  It is an error to attempt to
       delete a name that has inferior hierarchical names and also has
       the \Noselect mailbox name attribute (see the description of the
       LIST response for more details).
 
       It is permitted to delete a name that has inferior hierarchical
       names and does not have the \Noselect mailbox name attribute.  In
       this case, all messages in that mailbox are removed, and the name
       will acquire the \Noselect mailbox name attribute.
 
       The value of the highest-used unique identifier of the deleted
       mailbox MUST be preserved so that a new mailbox created with the
       same name will not reuse the identifiers of the former
       incarnation, UNLESS the new incarnation has a different unique
       identifier validity value.  See the description of the UID command
       for more detail.
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
    Examples:   C: A682 LIST "" *
                S: * LIST () "/" blurdybloop
                S: * LIST (\Noselect) "/" foo
                S: * LIST () "/" foo/bar
                S: A682 OK LIST completed
                C: A683 DELETE blurdybloop
                S: A683 OK DELETE completed
                C: A684 DELETE foo
                S: A684 NO Name "foo" has inferior hierarchical names
                C: A685 DELETE foo/bar
                S: A685 OK DELETE Completed
                C: A686 LIST "" *
                S: * LIST (\Noselect) "/" foo
                S: A686 OK LIST completed
                C: A687 DELETE foo
                S: A687 OK DELETE Completed
 
 
                C: A82 LIST "" *
                S: * LIST () "." blurdybloop
                S: * LIST () "." foo
                S: * LIST () "." foo.bar
                S: A82 OK LIST completed
                C: A83 DELETE blurdybloop
                S: A83 OK DELETE completed
                C: A84 DELETE foo
                S: A84 OK DELETE Completed
                C: A85 LIST "" *
                S: * LIST () "." foo.bar
                S: A85 OK LIST completed
                C: A86 LIST "" %
                S: * LIST (\Noselect) "." foo
                S: A86 OK LIST completed
 
 6.3.5.  RENAME Command
 
    Arguments:  existing mailbox name
                new mailbox name
 
    Responses:  no specific responses for this command
 
    Result:     OK - rename completed
                NO - rename failure: can't rename mailbox with that name,
                     can't rename to mailbox with that name
                BAD - command unknown or arguments invalid
 
       The RENAME command changes the name of a mailbox.  A tagged OK
       response is returned only if the mailbox has been renamed.  It is
 
 
 
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       an error to attempt to rename from a mailbox name that does not
       exist or to a mailbox name that already exists.  Any error in
       renaming will return a tagged NO response.
 
       If the name has inferior hierarchical names, then the inferior
       hierarchical names MUST also be renamed.  For example, a rename of
       "foo" to "zap" will rename "foo/bar" (assuming "/" is the
       hierarchy delimiter character) to "zap/bar".
 
       The value of the highest-used unique identifier of the old mailbox
       name MUST be preserved so that a new mailbox created with the same
       name will not reuse the identifiers of the former incarnation,
       UNLESS the new incarnation has a different unique identifier
       validity value.  See the description of the UID command for more
       detail.
 
       Renaming INBOX is permitted, and has special behavior.  It moves
       all messages in INBOX to a new mailbox with the given name,
       leaving INBOX empty.  If the server implementation supports
       inferior hierarchical names of INBOX, these are unaffected by a
       rename of INBOX.
 
    Examples:   C: A682 LIST "" *
                S: * LIST () "/" blurdybloop
                S: * LIST (\Noselect) "/" foo
                S: * LIST () "/" foo/bar
                S: A682 OK LIST completed
                C: A683 RENAME blurdybloop sarasoop
                S: A683 OK RENAME completed
                C: A684 RENAME foo zowie
                S: A684 OK RENAME Completed
                C: A685 LIST "" *
                S: * LIST () "/" sarasoop
                S: * LIST (\Noselect) "/" zowie
                S: * LIST () "/" zowie/bar
                S: A685 OK LIST completed
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
                C: Z432 LIST "" *
                S: * LIST () "." INBOX
                S: * LIST () "." INBOX.bar
                S: Z432 OK LIST completed
                C: Z433 RENAME INBOX old-mail
                S: Z433 OK RENAME completed
                C: Z434 LIST "" *
                S: * LIST () "." INBOX
                S: * LIST () "." INBOX.bar
                S: * LIST () "." old-mail
                S: Z434 OK LIST completed
 
 6.3.6.  SUBSCRIBE Command
 
    Arguments:  mailbox
 
    Responses:  no specific responses for this command
 
    Result:     OK - subscribe completed
                NO - subscribe failure: can't subscribe to that name
                BAD - command unknown or arguments invalid
 
       The SUBSCRIBE command adds the specified mailbox name to the
       server's set of "active" or "subscribed" mailboxes as returned by
       the LSUB command.  This command returns a tagged OK response only
       if the subscription is successful.
 
       A server MAY validate the mailbox argument to SUBSCRIBE to verify
       that it exists.  However, it MUST NOT unilaterally remove an
       existing mailbox name from the subscription list even if a mailbox
       by that name no longer exists.
 
       Note: this requirement is because some server sites may routinely
       remove a mailbox with a well-known name (e.g.  "system-alerts")
       after its contents expire, with the intention of recreating it
       when new contents are appropriate.
 
    Example:    C: A002 SUBSCRIBE #news.comp.mail.mime
                S: A002 OK SUBSCRIBE completed
 
 
 
 
 
 
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 6.3.7.  UNSUBSCRIBE Command
 
    Arguments:  mailbox name
 
    Responses:  no specific responses for this command
 
    Result:     OK - unsubscribe completed
                NO - unsubscribe failure: can't unsubscribe that name
                BAD - command unknown or arguments invalid
 
       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.
 
    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
 
    Responses:  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 client.  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.
 
       The LIST command SHOULD return its data quickly, without undue
       delay.  For example, it SHOULD NOT go to excess trouble to
       calculate \Marked or \Unmarked status or perform other processing;
       if each name requires 1 second of processing, then a list of 1200
       names would take 20 minutes!
 
       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.
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       An empty ("" string) mailbox name argument is a special request to
       return the hierarchy delimiter and the root name of the name given
       in the reference.  The value returned as the root MAY be null if
       the reference is non-rooted or is null.  In all cases, the
       hierarchy delimiter is returned.  This permits a client to get the
       hierarchy delimiter even when no mailboxes by that name currently
       exist.
 
       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.
 
       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 details).
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       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
       INBOX is supported by this server for this user and if the
       uppercase string "INBOX" matches the interpreted reference and
       mailbox name arguments with wildcards as described above.  The
       criteria for omitting INBOX is whether SELECT INBOX will return
       failure; it is not relevant whether the user's real INBOX resides
       on this or some other server.
 
    Example:    C: A101 LIST "" ""
                S: * LIST (\Noselect) "/" ""
                S: A101 OK LIST Completed
                C: A102 LIST #news.comp.mail.misc ""
                S: * LIST (\Noselect) "." #news.
                S: A102 OK LIST Completed
                C: A103 LIST /usr/staff/jones ""
                S: * LIST (\Noselect) "/" /
                S: A103 OK LIST Completed
                C: A202 LIST ~/Mail/ %
                S: * LIST (\Noselect) "/" ~/Mail/foo
                S: * LIST () "/" ~/Mail/meetings
                S: A202 OK LIST completed
 
 6.3.9.  LSUB Command
 
    Arguments:  reference name
                mailbox name with possible wildcards
 
    Responses:  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.
 
       A server MAY validate the subscribed names to see if they still
       exist.  If a name does not exist, it SHOULD be flagged with the
       \Noselect attribute in the LSUB response.  The server MUST NOT
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       unilaterally remove an existing mailbox name from the subscription
       list even if a mailbox by that name no longer exists.
 
    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. STATUS Command
 
    Arguments:  mailbox name
                status data item names
 
    Responses:  untagged responses: STATUS
 
    Result:     OK - status completed
                NO - status failure: no status for that name
                BAD - command unknown or arguments invalid
 
       The STATUS command requests the status of the indicated mailbox.
       It does not change the currently selected mailbox, nor does it
       affect the state of any messages in the queried mailbox (in
       particular, STATUS MUST NOT cause messages to lose the \Recent
       flag).
 
       The STATUS command provides an alternative to opening a second
       IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
       query that mailbox's status without deselecting the current
       mailbox in the first IMAP4rev1 connection.
 
       Unlike the LIST command, the STATUS command is not guaranteed to
       be fast in its response.  In some implementations, the server is
       obliged to open the mailbox read-only internally to obtain certain
       status information.  Also unlike the LIST command, the STATUS
       command does not accept wildcards.
 
       The currently defined status data items that can be requested are:
 
       MESSAGES       The number of messages in the mailbox.
 
       RECENT         The number of messages with the \Recent flag set.
 
       UIDNEXT        The next UID value that will be assigned to a new
                      message in the mailbox.  It is guaranteed that this
                      value will not change unless new messages are added
                      to the mailbox; and that it will change when new
                      messages are added even if those new messages are
                      subsequently expunged.
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       UIDVALIDITY    The unique identifier validity value of the
                      mailbox.
 
       UNSEEN         The number of messages which do not have the \Seen
                      flag set.
 
 
       Example:    C: A042 STATUS blurdybloop (UIDNEXT MESSAGES)
                   S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
                   S: A042 OK STATUS completed
 
 6.3.11. APPEND Command
 
    Arguments:  mailbox name
                OPTIONAL flag parenthesized list
                OPTIONAL date/time string
                message literal
 
    Responses:  no specific responses for this command
 
    Result:     OK - append completed
                NO - append error: can't append to that mailbox, error
                     in flags or date/time or message text
                BAD - command unknown or arguments invalid
 
       The APPEND command appends the literal argument as a new message
       to the end of the specified destination mailbox.  This argument
       SHOULD be in the format of 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 a [MIME-IMB] content
       transfer encoding.
 
       Note: There MAY be exceptions, e.g. draft messages, in which
       required [RFC-822] header lines are omitted in the message literal
       argument to APPEND.  The full implications of doing so MUST be
       understood and carefully weighed.
 
    If a flag parenthesized list is specified, the flags SHOULD be set in
    the resulting message; otherwise, the flag list of the resulting
    message is set empty by default.
 
    If a date_time is specified, the internal date SHOULD be set in the
    resulting message; otherwise, the internal date of the resulting
    message is set to the current date and time by default.
 
 
 
 
 
 
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    If the append is unsuccessful for any reason, the mailbox MUST be
    restored to its state before the APPEND attempt; no partial appending
    is permitted.
 
    If the destination mailbox does not exist, a server MUST return an
    error, and MUST NOT automatically create the mailbox.  Unless it is
    certain that the destination mailbox can not be created, the server
    MUST send the response code "[TRYCREATE]" as the prefix of the text
    of the tagged NO response.  This gives a hint to the client that it
    can attempt a CREATE command and retry the APPEND if the CREATE is
    successful.
 
    If the mailbox is currently selected, the normal new mail actions
    SHOULD occur.  Specifically, the server SHOULD notify the client
    immediately via an untagged EXISTS response.  If the server does not
    do so, the client MAY issue a NOOP command (or failing that, a CHECK
    command) after one or more APPEND commands.
 
    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, STATUS, and
    APPEND), the following commands are valid in the selected state:
    CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 6.4.1.  CHECK Command
 
    Arguments:  none
 
    Responses:  no specific responses 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
 
    Responses:  no specific responses 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 if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT
       command MAY be issued without previously issuing a CLOSE command.
       The SELECT, EXAMINE, and LOGOUT commands implicitly close the
       currently selected mailbox without doing an expunge.  However,
       when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       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
 
    Responses:  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.
 
 6.4.4.  SEARCH Command
 
    Arguments:  OPTIONAL [CHARSET] specification
                searching criteria (one or more)
 
    Responses:  REQUIRED untagged response: SEARCH
 
    Result:     OK - search completed
                NO - search error: can't search that [CHARSET] or
                     criteria
                BAD - command unknown or arguments invalid
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       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 can 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-IMB] body parts with
       terminal content media types other than TEXT and MESSAGE from
       consideration in SEARCH matching.
 
       The OPTIONAL [CHARSET] specification consists of the word
       "CHARSET" followed by a registered [CHARSET].  It indicates the
       [CHARSET] of the strings that appear in the search criteria.
       [MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
       [RFC-822]/[MIME-IMB] headers, MUST be decoded before comparing
       text in a [CHARSET] other than US-ASCII.  US-ASCII MUST be
       supported; other [CHARSET]s MAY be supported.  If the server does
       not support the specified [CHARSET], it MUST return a tagged NO
       response (not a BAD).
 
       In all search keys that use strings, a message matches the key if
       the string is a substring of the field.  The matching is case-
       insensitive.
 
       The 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.
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       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 [RFC-822] size larger than the
                      specified number of octets.
 
       NEW            Messages that have the \Recent flag set but not the
                      \Seen flag.  This is functionally equivalent to
                      "(RECENT UNSEEN)".
 
       NOT <search-key>
                      Messages that do not match the specified search
                      key.
 
       OLD            Messages that do not have the \Recent flag set.
                      This is functionally equivalent to "NOT RECENT" (as
                      opposed to "NOT NEW").
 
       ON <date>      Messages whose internal date is within the
                      specified date.
 
       OR <search-key1> <search-key2>
                      Messages that match either search key.
 
       RECENT         Messages that have the \Recent flag set.
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       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 [RFC-822] 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.
 
       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.
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
    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
 
    Responses:  untagged responses: FETCH
 
    Result:     OK - fetch completed
                NO - fetch error: can't fetch that data
                BAD - command unknown or arguments invalid
 
       The FETCH command retrieves data associated with a message in the
       mailbox.  The data items to be fetched can be either a single atom
       or a parenthesized list.
 
       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>]<<partial>>
                      The text of a particular body section.  The section
                      specification is a set of zero or more part
                      specifiers delimited by periods.  A part specifier
                      is either a part number or one of the following:
                      HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, MIME, and
                      TEXT.  An empty section specification refers to the
                      entire message, including the header.
 
                      Every message has at least one part number.
                      Non-[MIME-IMB] messages, and non-multipart
                      [MIME-IMB] messages with no encapsulated message,
                      only have a part 1.
 
                      Multipart messages are assigned consecutive part
                      numbers, as they occur in the message.  If a
                      particular part is of type message or multipart,
                      its parts MUST be indicated by a period followed by
                      the part number within that nested multipart part.
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
                      A part of type MESSAGE/RFC822 also has nested part
                      numbers, referring to parts of the MESSAGE part's
                      body.
 
                      The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and
                      TEXT part specifiers can be the sole part specifier
                      or can be prefixed by one or more numeric part
                      specifiers, provided that the numeric part
                      specifier refers to a part of type MESSAGE/RFC822.
                      The MIME part specifier MUST be prefixed by one or
                      more numeric part specifiers.
 
                      The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT
                      part specifiers refer to the [RFC-822] header of
                      the message or of an encapsulated [MIME-IMT]
                      MESSAGE/RFC822 message.  HEADER.FIELDS and
                      HEADER.FIELDS.NOT are followed by a list of
                      field-name (as defined in [RFC-822]) names, and
                      return a subset of the header.  The subset returned
                      by HEADER.FIELDS contains only those header fields
                      with a field-name that matches one of the names in
                      the list; similarly, the subset returned by
                      HEADER.FIELDS.NOT contains only the header fields
                      with a non-matching field-name.  The field-matching
                      is case-insensitive but otherwise exact.  In all
                      cases, the delimiting blank line between the header
                      and the body is always included.
 
                      The MIME part specifier refers to the [MIME-IMB]
                      header for this part.
 
                      The TEXT part specifier refers to the text body of
                      the message, omitting the [RFC-822] header.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
                        Here is an example of a complex message
                        with some of its part specifiers:
 
                         HEADER     ([RFC-822] header of the message)
                         TEXT       MULTIPART/MIXED
                         1          TEXT/PLAIN
                         2          APPLICATION/OCTET-STREAM
                         3          MESSAGE/RFC822
                         3.HEADER   ([RFC-822] header of the message)
                         3.TEXT     ([RFC-822] text body of the message)
                         3.1        TEXT/PLAIN
                         3.2        APPLICATION/OCTET-STREAM
                         4          MULTIPART/MIXED
                         4.1        IMAGE/GIF
                         4.1.MIME   ([MIME-IMB] header for the IMAGE/GIF)
                         4.2        MESSAGE/RFC822
                         4.2.HEADER ([RFC-822] header of the message)
                         4.2.TEXT   ([RFC-822] text body of the message)
                         4.2.1      TEXT/PLAIN
                         4.2.2      MULTIPART/ALTERNATIVE
                         4.2.2.1    TEXT/PLAIN
                         4.2.2.2    TEXT/RICHTEXT
 
 
                      It is possible to fetch a substring of the
                      designated text.  This is done by appending an open
                      angle bracket ("<"), the octet position of the
                      first desired octet, a period, the maximum number
                      of octets desired, and a close angle bracket (">")
                      to the part specifier.  If the starting octet is
                      beyond the end of the text, an empty string is
                      returned.
 
                      Any partial fetch that attempts to read beyond the
                      end of the text is truncated as appropriate.  A
                      partial fetch that starts at octet 0 is returned as
                      a partial fetch, even if this truncation happened.
 
                           Note: this means that BODY[]<0.2048> of a
                           1500-octet message will return BODY[]<0>
                           with a literal of size 1500, not BODY[].
 
                           Note: a substring fetch of a
                           HEADER.FIELDS or HEADER.FIELDS.NOT part
                           specifier is calculated after subsetting
                           the header.
 
 
 
 
 
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                      The \Seen flag is implicitly set; if this causes
                      the flags to change they SHOULD be included as part
                      of the FETCH responses.
 
       BODY.PEEK[<section>]<<partial>>
                      An alternate form of BODY[<section>] that does not
                      implicitly set the \Seen flag.
 
       BODYSTRUCTURE  The [MIME-IMB] body structure of the message.  This
                      is computed by the server by parsing the [MIME-IMB]
                      header fields in the [RFC-822] header and
                      [MIME-IMB] headers.
 
       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 internal date of the message.
 
       RFC822         Functionally equivalent to BODY[], differing in the
                      syntax of the resulting untagged FETCH data (RFC822
                      is returned).
 
       RFC822.HEADER  Functionally equivalent to BODY.PEEK[HEADER],
                      differing in the syntax of the resulting untagged
                      FETCH data (RFC822.HEADER is returned).
 
       RFC822.SIZE    The [RFC-822] size of the message.
 
       RFC822.TEXT    Functionally equivalent to BODY[TEXT], differing in
                      the syntax of the resulting untagged FETCH data
                      (RFC822.TEXT is returned).
 
       UID            The unique identifier for the message.
 
 
 
 
 
 
 
 
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    Example:    C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
                S: * 2 FETCH ....
                S: * 3 FETCH ....
                S: * 4 FETCH ....
                S: A654 OK FETCH completed
 
 6.4.6.  STORE Command
 
    Arguments:  message set
                message data item name
                value for message data item
 
    Responses:  untagged responses: FETCH
 
    Result:     OK - store completed
                NO - store error: can't store that data
                BAD - command unknown or arguments invalid
 
       The STORE command alters data associated with a message in the
       mailbox.  Normally, STORE will return the updated value of the
       data with an untagged FETCH response.  A suffix of ".SILENT" in
       the data item name prevents the untagged FETCH, and the server
       SHOULD assume that the client has determined the updated value
       itself or does not care about the updated value.
 
          Note: regardless of whether or not the ".SILENT" suffix was
          used, the server SHOULD send an untagged FETCH response if a
          change to a message's flags from an external source is
          observed.  The intent is that the status of the flags is
          determinate without a race condition.
 
       The currently defined data items that can be stored are:
 
       FLAGS <flag list>
                      Replace the flags for the message 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.
 
 
 
 
 
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       +FLAGS.SILENT <flag list>
                      Equivalent to +FLAGS, but without returning a new
                      value.
 
       -FLAGS <flag list>
                      Remove the argument from the flags for the message.
                      The new value of the flags are returned as if a
                      FETCH of those flags was done.
 
       -FLAGS.SILENT <flag list>
                      Equivalent to -FLAGS, but without returning a new
                      value.
 
    Example:    C: A003 STORE 2:4 +FLAGS (\Deleted)
                S: * 2 FETCH FLAGS (\Deleted \Seen)
                S: * 3 FETCH FLAGS (\Deleted)
                S: * 4 FETCH FLAGS (\Deleted \Flagged \Seen)
                S: A003 OK STORE completed
 
 6.4.7.  COPY Command
 
    Arguments:  message set
                mailbox name
 
    Responses:  no specific responses for this command
 
    Result:     OK - copy completed
                NO - copy error: can't copy those messages or to that
                     name
                BAD - command unknown or arguments invalid
 
       The COPY command copies the specified message(s) to the end of the
       specified destination mailbox.  The flags and internal date of the
       message(s) SHOULD be preserved 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.
 
 
 
 
 
 
 
 
 
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       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
 
 6.4.8.  UID Command
 
    Arguments:  command name
                command arguments
 
    Responses:  untagged responses: FETCH, SEARCH
 
    Result:     OK - UID command completed
                NO - UID command error
                BAD - command unknown or arguments invalid
 
       The UID command has two forms.  In the first form, it takes as its
       arguments a COPY, FETCH, or STORE command with arguments
       appropriate for the associated command.  However, the numbers in
       the message set argument are unique identifiers instead of message
       sequence numbers.
 
       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.
 
       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 a UID was specified
       as a message data item to the FETCH.
 
 
 
 
 
 
 
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    Example:    C: A999 UID FETCH 4827313:4828442 FLAGS
                S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
                S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
                S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
                S: A999 UID FETCH completed
 
 6.5.    Client Commands - Experimental/Expansion
 
 6.5.1.  X<atom> Command
 
    Arguments:  implementation defined
 
    Responses:  implementation defined
 
    Result:     OK - command completed
                NO - failure
                BAD - command unknown or arguments invalid
 
       Any command prefixed with an X is an experimental command.
       Commands which are not part of this specification, a standard or
       standards-track revision of this specification, or an IESG-
       approved experimental protocol, MUST use the X prefix.
 
       Any added untagged responses issued by an experimental command
       MUST also be prefixed with an X.  Server implementations MUST NOT
       send any such untagged responses, unless the client requested it
       by issuing the associated experimental command.
 
    Example:    C: a441 CAPABILITY
                S: * CAPABILITY IMAP4rev1 AUTH=KERBEROS_V4 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
 
 7.      Server Responses
 
    Server responses are in three forms: status responses, server data,
    and command continuation request.  The information contained in a
    server response, identified by "Contents:" in the response
    descriptions below, is described by function, not by syntax.  The
    precise syntax of server responses is described in the Formal Syntax
    section.
 
    The client MUST be prepared to accept any response at all times.
 
 
 
 
 
 
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    Status responses can be tagged or untagged.  Tagged status responses
    indicate the completion result (OK, NO, or BAD status) of a client
    command, and have a tag matching the command.
 
    Some status responses, and all server data, are untagged.  An
    untagged response is indicated by the token "*" instead of a tag.
    Untagged status responses indicate server greeting, or server status
    that does not indicate the completion of a command (for example, an
    impending system shutdown alert).  For historical reasons, untagged
    server data responses are also called "unsolicited data", although
    strictly speaking only unilateral server data is truly "unsolicited".
 
    Certain server data MUST be recorded by the client when it is
    received; this is noted in the description of that data.  Such data
    conveys critical information which affects the interpretation of all
    subsequent commands and responses (e.g. updates reflecting the
    creation or destruction of messages).
 
    Other server data SHOULD be recorded for later reference; if the
    client does not need to record the data, or if recording the data has
    no obvious purpose (e.g. a SEARCH response when no SEARCH command is
    in progress), the data SHOULD be ignored.
 
    An example of unilateral untagged server data occurs when the IMAP
    connection is in selected state.  In selected state, the server
    checks the mailbox for new messages as part of command execution.
    Normally, this is part of the execution of every command; hence, a
    NOOP command suffices to check for new messages.  If new messages are
    found, the server sends untagged EXISTS and RECENT responses
    reflecting the new size of the mailbox.  Server implementations that
    offer multiple simultaneous access to the same mailbox SHOULD also
    send appropriate unilateral untagged FETCH and EXPUNGE responses if
    another agent changes the state of any message flags or expunges any
    messages.
 
    Command continuation request responses use the token "+" instead of a
    tag.  These responses are sent by the server to indicate acceptance
    of an incomplete client command and readiness for the remainder of
    the command.
 
 7.1.    Server Responses - Status Responses
 
    Status responses are OK, NO, BAD, PREAUTH and BYE.  OK, NO, and BAD
    may be tagged or untagged.  PREAUTH and BYE are always untagged.
 
    Status responses MAY include an OPTIONAL "response code".  A response
    code consists of data inside square brackets in the form of an atom,
    possibly followed by a space and arguments.  The response code
 
 
 
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    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.
 
       NEWNAME        Followed by a mailbox name and a new mailbox name.
                      A SELECT or EXAMINE is failing because the target
                      mailbox name no longer exists because it was
                      renamed to the new mailbox name.  This is a hint to
                      the client that the operation can succeed if the
                      SELECT or EXAMINE is reissued with the new mailbox
                      name.
 
       PARSE          The human-readable text represents an error in
                      parsing the [RFC-822] header or [MIME-IMB] headers
                      of a message in the mailbox.
 
       PERMANENTFLAGS Followed by a parenthesized list of flags,
                      indicates which of the known flags that the client
                      can change permanently.  Any flags that are in the
                      FLAGS untagged response, but not the PERMANENTFLAGS
                      list, can not be set permanently.  If the client
                      attempts to STORE a flag that is not in the
                      PERMANENTFLAGS list, the server will either reject
                      it with a NO reply or store the state for the
                      remainder of the current session only.  The
                      PERMANENTFLAGS list can also include the special
                      flag \*, which indicates that it is possible to
                      create new keywords by attempting to store those
                      flags in the mailbox.
 
       READ-ONLY      The mailbox is selected read-only, or its access
                      while selected has changed from read-write to
                      read-only.
 
       READ-WRITE     The mailbox is selected read-write, or its access
                      while selected has changed from read-only to
                      read-write.
 
 
 
 
 
 
 
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       TRYCREATE      An APPEND or COPY attempt is failing because the
                      target mailbox does not exist (as opposed to some
                      other reason).  This is a hint to the client that
                      the operation can succeed if the mailbox is first
                      created by the CREATE command.
 
       UIDVALIDITY    Followed by a decimal number, indicates the unique
                      identifier validity value.
 
       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
 
    Contents:   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 connection startup.  It indicates that the connection is not
       yet authenticated and that a LOGIN command is needed.
 
    Example:    S: * OK IMAP4rev1 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
 
       Contents:   OPTIONAL response code
                   human-readable text
 
       The NO response indicates an operational error message from the
       server.  When tagged, it indicates unsuccessful completion of the
       associated command.  The untagged form indicates a warning; the
       command can still complete successfully.  The human-readable text
       describes the condition.
 
 
 
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    Example:    C: A222 COPY 1:2 owatagusiam
                S: * NO Disk is 98% full, please delete unnecessary data
                S: A222 OK COPY completed
                C: A223 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: A223 NO COPY failed: disk is full
 
 7.1.3.  BAD Response
 
    Contents:   OPTIONAL response code
                human-readable text
 
       The BAD response indicates an error message from the server.  When
       tagged, it reports a protocol-level error in the client's command;
       the tag indicates the command that caused the error.  The untagged
       form indicates a protocol-level error for which the associated
       command can not be determined; it can also indicate an internal
       server failure.  The human-readable text describes the condition.
 
    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
 
    Contents:   OPTIONAL response code
                human-readable text
 
       The PREAUTH response is always untagged, and is one of three
       possible greetings at connection startup.  It indicates that the
       connection has already been authenticated by external means and
       thus no LOGIN command is needed.
 
    Example:    S: * PREAUTH IMAP4rev1 server logged in as Smith
 
 7.1.5.  BYE Response
 
    Contents:   OPTIONAL response code
                human-readable text
 
 
 
 
 
 
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       The BYE response is always untagged, and indicates that the server
       is about to close the connection.  The human-readable text MAY be
       displayed to the user in a status report by the client.  The BYE
       response is sent under one of four conditions:
 
          1) as part of a normal logout sequence.  The server will close
             the connection after sending the tagged OK response to the
             LOGOUT command.
 
          2) as a panic shutdown announcement.  The server closes the
             connection immediately.
 
          3) as an announcement of an inactivity autologout.  The server
             closes the connection immediately.
 
          4) as one of three possible greetings at connection startup,
             indicating that the server is not willing to accept a
             connection from this client.  The server closes the
             connection immediately.
 
       The difference between a BYE that occurs as part of a normal
       LOGOUT sequence (the first case) and a BYE that occurs because of
       a failure (the other three cases) is that the connection closes
       immediately in the failure case.
 
    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 and mailbox
    status data are transmitted from the server to the client.  Many of
    these responses typically result from a command with the same name.
 
 7.2.1.  CAPABILITY Response
 
    Contents:   capability listing
 
       The CAPABILITY response occurs as a result of a CAPABILITY
       command.  The capability listing contains a space-separated
       listing of capability names that the server supports.  The
       capability listing MUST include the atom "IMAP4rev1".
 
       A capability name which begins with "AUTH=" indicates that the
       server supports that particular authentication mechanism.
 
 
 
 
 
 
 
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       Other capability names indicate that the server supports an
       extension, revision, or amendment to the IMAP4rev1 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 IMAP4rev1 extensions, revisions, or amendments
       registered with IANA.  A server MUST NOT offer unregistered or
       non-standard capability names, unless such names are prefixed with
       an "X".
 
       Client implementations SHOULD NOT require any capability name
       other than "IMAP4rev1", and MUST ignore any unknown capability
       names.
 
    Example:    S: * CAPABILITY IMAP4rev1 AUTH=KERBEROS_V4 XPIG-LATIN
 
 7.2.2.  LIST Response
 
    Contents:   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
       can 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.
 
 
 
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       The hierarchy delimiter is a character used to delimit levels of
       hierarchy in a mailbox name.  A client can use it to create child
       mailboxes, and to search higher or lower levels of naming
       hierarchy.  All children of a top-level hierarchy node MUST use
       the same separator character.  A NIL hierarchy delimiter means
       that no hierarchy exists; the name is a "flat" name.
 
       The name represents an unambiguous left-to-right hierarchy, and
       MUST be valid for use as a reference in LIST and LSUB commands.
       Unless \Noselect is indicated, the name MUST also be valid as an
             argument for commands, such as SELECT, that accept mailbox
       names.
 
    Example:    S: * LIST (\Noselect) "/" ~/Mail/foo
 
 7.2.3.  LSUB Response
 
    Contents:   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
       can 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   STATUS Response
 
    Contents:   name
                status parenthesized list
 
       The STATUS response occurs as a result of an STATUS command.  It
       returns the mailbox name that matches the STATUS specification and
       the requested mailbox status information.
 
    Example:    S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
 
 7.2.5.  SEARCH Response
 
    Contents:   zero or more numbers
 
 
 
 
 
 
 
 
 
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       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
 
 7.2.6.  FLAGS Response
 
    Contents:   flag parenthesized list
 
       The FLAGS response occurs as a result of a SELECT or EXAMINE
       command.  The flag parenthesized list identifies the flags (at a
       minimum, the system-defined flags) that are applicable for this
       mailbox.  Flags other than the system flags can also exist,
       depending on server implementation.
 
       The update from the FLAGS response MUST be recorded by the client.
 
    Example:    S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
 
 7.3.    Server Responses - Mailbox Size
 
    These responses are always untagged.  This is how changes in the size
    of the mailbox are trasnmitted from the server to the client.
    Immediately following the "*" token is a number that represents a
    message count.
 
 7.3.1.  EXISTS Response
 
    Contents:   none
 
       The EXISTS response reports the number of messages in the mailbox.
       This response occurs as a result of a SELECT or EXAMINE command,
       and if the size of the mailbox changes (e.g. new mail).
 
       The update from the EXISTS response MUST be recorded by the
       client.
 
    Example:    S: * 23 EXISTS
 
 
 
 
 
 
 
 
 
 
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 7.3.2.  RECENT Response
 
       Contents:   none
 
       The RECENT response reports the number of messages with the
       \Recent flag set.  This response occurs as a result of a SELECT or
       EXAMINE command, and if the size of the mailbox changes (e.g. new
       mail).
 
          Note: It is not guaranteed that the message sequence numbers of
          recent messages will be a contiguous range of the highest n
          messages in the mailbox (where n is the value reported by the
          RECENT response).  Examples of situations in which this is not
          the case are: multiple clients having the same mailbox open
          (the first session to be notified will see it as recent, others
          will probably see it as non-recent), and when the mailbox is
          re-ordered by a non-IMAP agent.
 
          The only reliable way to identify recent messages is to look at
          message flags to see which have the \Recent flag set, or to do
          a SEARCH RECENT.
 
          The update from the RECENT response MUST be recorded by the
          client.
 
    Example:    S: * 5 RECENT
 
 7.4.    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 a message sequence number.
 
 7.4.1.  EXPUNGE Response
 
    Contents:   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).
 
       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
 
 
 
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       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
 
 7.4.2.  FETCH Response
 
    Contents:   message data
 
       The FETCH response returns data about a message to the client.
       The data are pairs of data item names and their values in
       parentheses.  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>]<<origin_octet>>
                      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.
 
                      If the origin octet is specified, this string is a
                      substring of the entire body contents, starting at
                      that origin octet.  This means that BODY[]<0> MAY
                      be truncated, but BODY[] is NEVER truncated.
 
                      8-bit textual data is permitted if a [CHARSET]
                      identifier is part of the body parameter
                      parenthesized list for this section.  Note that
                      headers (part specifiers HEADER or MIME, or the
                      header portion of a MESSAGE/RFC822 part), MUST be
 
 
 
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                      7-bit; 8-bit characters are not permitted in
                      headers.  Note also that the blank line at the end
                      of the header is always included in header data.
 
                      Non-textual data such as binary data MUST be
                      transfer encoded into a textual form such as BASE64
                      prior to being sent to the client.  To derive the
                      original binary data, the client MUST decode the
                      transfer encoded string.
 
       BODYSTRUCTURE  A parenthesized list that describes the [MIME-IMB]
                      body structure of a message.  This is computed by
                      the server by parsing the [MIME-IMB] header fields,
                      defaulting various fields as necessary.
 
                      For example, a simple text message of 48 lines and
                      2279 octets can have a body structure of: ("TEXT"
                      "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 2279
                      48)
 
                      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.).
 
                      For example, a two part message consisting of a
                      text and a BASE645-encoded text attachment can have
                      a body structure of: (("TEXT" "PLAIN" ("CHARSET"
                      "US-ASCII") NIL NIL "7BIT" 1152 23)("TEXT" "PLAIN"
                      ("CHARSET" "US-ASCII" "NAME" "cc.diff")
                      "<960723163407.20117h@cac.washington.edu>"
                      "Compiler diff" "BASE64" 4554 73) "MIXED"))
 
                      Extension data follows the multipart subtype.
                      Extension data is never returned with the BODY
                      fetch, but can 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
 
 
 
 Crispin                     Standards Track                    [Page 59]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
                         "baz"] as defined in [MIME-IMB].
 
                      body disposition
                         A parenthesized list, consisting of a
                         disposition type string followed by a
                         parenthesized list of disposition
                         attribute/value pairs.  The disposition type and
                         attribute names will be defined in a future
                         standards-track revision to [DISPOSITION].
 
                      body language
                         A string or parenthesized list giving the body
                         language value as defined in [LANGUAGE-TAGS].
 
                      Any following extension data are not yet defined in
                      this version of the protocol.  Such extension data
                      can 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 media type name as
                         defined in [MIME-IMB].
 
                      body subtype
                         A string giving the content subtype name as
                         defined in [MIME-IMB].
 
                      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-IMB].
 
                      body id
                         A string giving the content id as defined in
                         [MIME-IMB].
 
                      body description
                         A string giving the content description as
                         defined in [MIME-IMB].
 
 
 
 Crispin                     Standards Track                    [Page 60]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
                      body encoding
                         A string giving the content transfer encoding as
                         defined in [MIME-IMB].
 
                      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
                      content 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 can be
                      returned with a BODYSTRUCTURE fetch.  Extension
                      data, if present, MUST be in the defined order.
 
                      The extension data of a non-multipart body part are
                      in the following order:
 
                      body MD5
                         A string giving the body MD5 value as defined in
                         [MD5].
 
                      body disposition
                         A parenthesized list with the same content and
                         function as the body disposition for a multipart
                         body part.
 
                      body language
                         A string or parenthesized list giving the body
                         language value as defined in [LANGUAGE-TAGS].
 
                      Any following extension data are not yet defined in
                      this version of the protocol, and would be as
                      described above under multipart extension data.
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
       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.
 
       FLAGS          A parenthesized list of flags that are set for this
                      message.
 
       INTERNALDATE   A string representing the internal date of the
                      message.
 
       RFC822         Equivalent to BODY[].
 
       RFC822.HEADER  Equivalent to BODY.PEEK[HEADER].
 
       RFC822.SIZE    A number expressing the [RFC-822] size of the
                      message.
 
       RFC822.TEXT    Equivalent to BODY[TEXT].
 
 
 
 Crispin                     Standards Track                    [Page 62]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
       UID            A number expressing the unique identifier of the
                      message.
 
 
    Example:    S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827)
 
 7.5.    Server Responses - Command Continuation Request
 
    The command continuation request response is indicated by a "+" token
    instead of a tag.  This form of response indicates that the server is
    ready to accept the continuation of a command from the client.  The
    remainder of this response is a line of text.
 
    This response is used in the 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"
 
 8.      Sample IMAP4rev1 connection
 
    The following is a transcript of an IMAP4rev1 connection.  A long
    line in this sample is broken for editorial clarity.
 
 S:   * OK IMAP4rev1 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
 
 
 
 Crispin                     Standards Track                    [Page 63]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
 S:   a002 OK [READ-WRITE] SELECT completed
 C:   a003 fetch 12 full
 S:   * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"
       RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)"
       "IMAP4rev1 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 body[header]
 S:    * 12 FETCH (BODY[HEADER] {350}
 S:    Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT)
 S:    From: Terry Gray <gray@cac.washington.edu>
 S:    Subject: IMAP4rev1 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 IMAP4rev1 server terminating connection
 S:    a006 OK LOGOUT completed
 
 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 one or more commas.
 
    In the case of alternative or optional rules in which a later rule
    overlaps an earlier rule, the rule which is listed earlier MUST take
    priority.  For example, "\Seen" when parsed as a flag is the \Seen
    flag name and not a flag_extension, even though "\Seen" could be
    parsed as a flag_extension.  Some, but not all, instances of this
    rule are noted below.
 
 
 
 
 Crispin                     Standards Track                    [Page 64]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
    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.
 
 address         ::= "(" addr_name SPACE addr_adl SPACE addr_mailbox
                     SPACE addr_host ")"
 
 addr_adl        ::= nstring
                     ;; Holds route from [RFC-822] route-addr if
                     ;; non-NIL
 
 addr_host       ::= nstring
                     ;; NIL indicates [RFC-822] group syntax.
                     ;; Otherwise, holds [RFC-822] domain name
 
 addr_mailbox    ::= nstring
                     ;; NIL indicates end of [RFC-822] group; if
                     ;; non-NIL and addr_host is NIL, holds
                     ;; [RFC-822] group name.
                     ;; Otherwise, holds [RFC-822] local-part
 
 addr_name       ::= nstring
                     ;; Holds phrase from [RFC-822] mailbox if
                     ;; non-NIL
 
 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
 
 atom            ::= 1*ATOM_CHAR
 
 ATOM_CHAR       ::= <any CHAR except atom_specials>
 
 atom_specials   ::= "(" / ")" / "{" / SPACE / CTL / list_wildcards /
                     quoted_specials
 
 
 
 
 Crispin                     Standards Track                    [Page 65]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
 authenticate    ::= "AUTHENTICATE" SPACE auth_type *(CRLF base64)
 
 auth_type       ::= atom
                     ;; Defined by [IMAP-AUTH]
 
 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 body_fld_dsp
                     [SPACE body_fld_lang
                     [SPACE 1#body_extension]]]
                     ;; MUST NOT be returned on non-extensible
                     ;; "BODY" fetch
 
 body_ext_mpart  ::= body_fld_param
                     [SPACE body_fld_dsp SPACE body_fld_lang
                     [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_dsp    ::= "(" string SPACE body_fld_param ")" / nil
 
 body_fld_enc    ::= (<"> ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
                     "QUOTED-PRINTABLE") <">) / string
 
 body_fld_id     ::= nstring
 
 body_fld_lang   ::= nstring / "(" 1#string ")"
 
 
 
 
 Crispin                     Standards Track                    [Page 66]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
 body_fld_lines  ::= number
 
 body_fld_md5    ::= nstring
 
 body_fld_octets ::= number
 
 body_fld_param  ::= "(" 1#(string SPACE string) ")" / nil
 
 body_type_1part ::= (body_type_basic / body_type_msg / body_type_text)
                     [SPACE body_ext_1part]
 
 body_type_basic ::= media_basic SPACE body_fields
                     ;; MESSAGE subtype MUST NOT be "RFC822"
 
 body_type_mpart ::= 1*body SPACE media_subtype
                     [SPACE body_ext_mpart]
 
 body_type_msg   ::= media_message SPACE body_fields SPACE envelope
                     SPACE body SPACE body_fld_lines
 
 body_type_text  ::= media_text SPACE body_fields SPACE body_fld_lines
 
 capability      ::= "AUTH=" auth_type / atom
                     ;; New capabilities MUST begin with "X" or be
                     ;; registered with IANA as standard or
                     ;; standards-track
 
 capability_data ::= "CAPABILITY" SPACE [1#capability SPACE] "IMAP4rev1"
                     [SPACE 1#capability]
                     ;; IMAP4rev1 servers which offer RFC 1730
                     ;; compatibility MUST list "IMAP4" as the first
                     ;; 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 / list / lsub /
                     rename / select / status / subscribe / unsubscribe
                     ;; Valid only in Authenticated or Selected state
 
 
 
 Crispin                     Standards Track                    [Page 67]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
 command_nonauth ::= login / authenticate
                     ;; Valid only when in Non-Authenticated state
 
 command_select  ::= "CHECK" / "CLOSE" / "EXPUNGE" /
                      copy / fetch / 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, 0x0D>
 
 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       ::= 4digit
 
 date_time       ::= <"> date_day_fixed "-" date_month "-" date_year
                     SPACE time SPACE zone <">
 
 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"
 
 
 
 
 
 Crispin                     Standards Track                    [Page 68]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
 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       ::= "ENVELOPE" / "FLAGS" / "INTERNALDATE" /
                     "RFC822" [".HEADER" / ".SIZE" / ".TEXT"] /
                     "BODY" ["STRUCTURE"] / "UID" /
                     "BODY" [".PEEK"] section
                     ["<" number "." nz_number ">"]
 
 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
 
 
 
 Crispin                     Standards Track                    [Page 69]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
 flag_list       ::= "(" #flag ")"
 
 greeting        ::= "*" SPACE (resp_cond_auth / resp_cond_bye) CRLF
 
 header_fld_name ::= astring
 
 header_list     ::= "(" 1#header_fld_name ")"
 
 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.  All case variants of
                     ;; INBOX (e.g. "iNbOx") MUST be interpreted as INBOX
                     ;; not as an astring.  Refer to section 5.1 for
                     ;; further semantic details of mailbox names.
 
 mailbox_data    ::=  "FLAGS" SPACE flag_list /
                      "LIST" SPACE mailbox_list /
                      "LSUB" SPACE mailbox_list /
                      "MAILBOX" SPACE text /
                      "SEARCH" [SPACE 1#nz_number] /
                      "STATUS" SPACE mailbox SPACE
                      "(" #<status_att number ")" /
                      number SPACE "EXISTS" / number SPACE "RECENT"
 
 mailbox_list    ::= "(" #("\Marked" / "\Noinferiors" /
                     "\Noselect" / "\Unmarked" / flag_extension) ")"
                     SPACE (<"> QUOTED_CHAR <"> / nil) SPACE mailbox
 
 media_basic     ::= (<"> ("APPLICATION" / "AUDIO" / "IMAGE" /
                     "MESSAGE" / "VIDEO") <">) / string)
                     SPACE media_subtype
                     ;; Defined in [MIME-IMT]
 
 media_message   ::= <"> "MESSAGE" <"> SPACE <"> "RFC822" <">
 
 
 
 Crispin                     Standards Track                    [Page 70]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
                     ;; Defined in [MIME-IMT]
 
 media_subtype   ::= string
                     ;; Defined in [MIME-IMT]
 
 media_text      ::= <"> "TEXT" <"> SPACE media_subtype
                     ;; Defined in [MIME-IMT]
 
 message_data    ::= nz_number SPACE ("EXPUNGE" /
                                     ("FETCH" SPACE msg_att))
 
 msg_att         ::= "(" 1#("ENVELOPE" SPACE envelope /
                     "FLAGS" SPACE "(" #(flag / "\Recent") ")" /
                     "INTERNALDATE" SPACE date_time /
                     "RFC822" [".HEADER" / ".TEXT"] SPACE nstring /
                     "RFC822.SIZE" SPACE number /
                     "BODY" ["STRUCTURE"] SPACE body /
                     "BODY" section ["<" number ">"] SPACE nstring /
                     "UID" SPACE uniqueid) ")"
 
 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)
 
 password        ::= astring
 
 quoted          ::= <"> *QUOTED_CHAR <">
 
 QUOTED_CHAR     ::= <any TEXT_CHAR except quoted_specials> /
                     "\" quoted_specials
 
 quoted_specials ::= <"> / "\"
 
 rename          ::= "RENAME" SPACE mailbox SPACE mailbox
                     ;; Use of INBOX as a destination gives a NO error
 
 response        ::= *(continue_req / response_data) response_done
 
 response_data   ::= "*" SPACE (resp_cond_state / resp_cond_bye /
                     mailbox_data / message_data / capability_data)
 
 
 
 Crispin                     Standards Track                    [Page 71]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
                     CRLF
 
 response_done   ::= response_tagged / response_fatal
 
 response_fatal  ::= "*" SPACE resp_cond_bye CRLF
                     ;; Server closes connection immediately
 
 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
 
 resp_cond_state ::= ("OK" / "NO" / "BAD") SPACE resp_text
                     ;; Status condition
 
 resp_text       ::= ["[" resp_text_code "]" SPACE] (text_mime2 / text)
                     ;; text SHOULD NOT begin with "[" or "="
 
 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]
                     1#search_key
                     ;; [CHARSET] MUST be registered with IANA
 
 search_key      ::= "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" /
                     ;; Above this line were in [IMAP2]
                     "DRAFT" /
                     "HEADER" SPACE header_fld_name 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 /
 
 
 
 Crispin                     Standards Track                    [Page 72]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
                     "UID" SPACE set / "UNDRAFT" / set /
                     "(" 1#search_key ")"
 
 section         ::= "[" [section_text / (nz_number *["." nz_number]
                     ["." (section_text / "MIME")])] "]"
 
 section_text    ::= "HEADER" / "HEADER.FIELDS" [".NOT"]
                     SPACE header_list / "TEXT"
 
 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>
 
 status          ::= "STATUS" SPACE mailbox SPACE "(" 1#status_att ")"
 
 status_att      ::= "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
                     "UNSEEN"
 
 store           ::= "STORE" SPACE set SPACE store_att_flags
 
 store_att_flags ::= (["+" / "-"] "FLAGS" [".SILENT"]) SPACE
                     (flag_list / #flag)
 
 string          ::= quoted / literal
 
 subscribe       ::= "SUBSCRIBE" SPACE mailbox
 
 tag             ::= 1*<any ATOM_CHAR except "+">
 
 text            ::= 1*TEXT_CHAR
 
 
 
 Crispin                     Standards Track                    [Page 73]
 
 RFC 2060                       IMAP4rev1                   December 1996
 
 
 text_mime2       ::= "=?" <charset> "?" <encoding> "?"
                      <encoded-text> "?="
                      ;; Syntax defined in [MIME-HDRS]
 
 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
 
 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".
 
 10.     Author's Note
 
    This document is a revision or rewrite of earlier documents, and
    supercedes the protocol specification in those documents: RFC 1730,
    unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064.
 
 11.     Security Considerations
 
    IMAP4rev1 protocol transactions, including electronic mail data, are
    sent in the clear over the network unless 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.
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
    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
    University of Washington
    4545 15th Aveneue NE
    Seattle, WA  98105-4527
 
    Phone: (206) 543-5762
 
    EMail: MRC@CAC.Washington.EDU
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 Appendices
 
 A.      References
 
 [ACAP] Myers, J. "ACAP -- Application Configuration Access Protocol",
 Work in Progress.
 
 [CHARSET] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2,
 RFC 1700, USC/Information Sciences Institute, October 1994.
 
 [DISPOSITION] Troost, R., and Dorner, S., "Communicating Presentation
 Information in Internet Messages: The Content-Disposition Header",
 RFC 1806, June 1995.
 
 [IMAP-AUTH] Myers, J., "IMAP4 Authentication Mechanism", RFC 1731.
 Carnegie-Mellon University, December 1994.
 
 [IMAP-COMPAT] Crispin, M., "IMAP4 Compatibility with IMAP2bis", RFC
 2061, University of Washington, November 1996.
 
 [IMAP-DISC] Austein, R., "Synchronization Operations for Disconnected
 IMAP4 Clients", Work in Progress.
 
 [IMAP-HISTORICAL] Crispin, M. "IMAP4 Compatibility with IMAP2 and
 IMAP2bis", RFC 1732, University of Washington, December 1994.
 
 [IMAP-MODEL] Crispin, M., "Distributed Electronic Mail Models in
 IMAP4", RFC 1733, University of Washington, December 1994.
 
 [IMAP-OBSOLETE] Crispin, M., "Internet Message Access Protocol -
 Obsolete Syntax", RFC 2062, University of Washington, November 1996.
 
 [IMAP2] Crispin, M., "Interactive Mail Access Protocol - Version 2",
 RFC 1176, University of Washington, August 1990.
 
 [LANGUAGE-TAGS] Alvestrand, H., "Tags for the Identification of
 Languages", RFC 1766, March 1995.
 
 [MD5] Myers, J., and M. Rose, "The Content-MD5 Header Field", RFC
 1864, October 1995.
 
 [MIME-IMB] Freed, N., and N. Borenstein, "MIME (Multipurpose Internet
 Mail Extensions) Part One: Format of Internet Message Bodies", RFC
 2045, November 1996.
 
 [MIME-IMT] Freed, N., and N. Borenstein, "MIME (Multipurpose
 Internet Mail Extensions) Part Two: Media Types", RFC 2046,
 November 1996.
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 [MIME-HDRS] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
 Part Three: Message Header Extensions for Non-ASCII Text", RFC
 2047, November 1996.
 
 [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
 Messages", STD 11, RFC 822, University of Delaware, August 1982.
 
 [SMTP] Postel, J., "Simple Mail Transfer Protocol", STD 10,
 RFC 821, USC/Information Sciences Institute, August 1982.
 
 [UTF-7] Goldsmith, D., and Davis, M., "UTF-7: A Mail-Safe
 Transformation Format of Unicode", RFC 1642, July 1994.
 
 B.      Changes from RFC 1730
 
 1) The STATUS command has been added.
 
 2) Clarify in the formal syntax that the "#" construct can never
 refer to multiple spaces.
 
 3) Obsolete syntax has been moved to a separate document.
 
 4) The PARTIAL command has been obsoleted.
 
 5) The RFC822.HEADER.LINES, RFC822.HEADER.LINES.NOT, RFC822.PEEK, and
 RFC822.TEXT.PEEK fetch attributes have been obsoleted.
 
 6) The "<" origin "." size ">" suffix for BODY text attributes has
 been added.
 
 7) The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, MIME, and TEXT part
 specifiers have been added.
 
 8) Support for Content-Disposition and Content-Language has been
 added.
 
 9) The restriction on fetching nested MULTIPART parts has been
 removed.
 
 10) Body part number 0 has been obsoleted.
 
 11) Server-supported authenticators are now identified by
 capabilities.
 
 
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 12) The capability that identifies this protocol is now called
 "IMAP4rev1".  A server that provides backwards support for RFC 1730
 SHOULD emit the "IMAP4" capability in addition to "IMAP4rev1" in its
 CAPABILITY response.  Because RFC-1730 required "IMAP4" to appear as
 the first capability, it MUST listed first in the response.
 
 13) A description of the mailbox name namespace convention has been
 added.
 
 14) A description of the international mailbox name convention has
 been added.
 
 15) The UID-NEXT and UID-VALIDITY status items are now called UIDNEXT
 and UIDVALIDITY.  This is a change from the IMAP STATUS
 Work in Progress and not from RFC-1730
 
 16) Add a clarification that a null mailbox name argument to the LIST
 command returns an untagged LIST response with the hierarchy
 delimiter and root of the reference argument.
 
 17) Define terms such as "MUST", "SHOULD", and "MUST NOT".
 
 18) Add a section which defines message attributes and more
 thoroughly details the semantics of message sequence numbers, UIDs,
 and flags.
 
 19) Add a clarification detailing the circumstances when a client may
 send multiple commands without waiting for a response, and the
 circumstances in which ambiguities may result.
 
 20) Add a recommendation on server behavior for DELETE and RENAME
 when inferior hierarchical names of the given name exist.
 
 21) Add a clarification that a mailbox name may not be unilaterally
 unsubscribed by the server, even if that mailbox name no longer
 exists.
 
 22) Add a clarification that LIST should return its results quickly
 without undue delay.
 
 23) Add a clarification that the date_time argument to APPEND sets
 the internal date of the message.
 
 24) Add a clarification on APPEND behavior when the target mailbox is
 the currently selected mailbox.
 
 
 
 
 
 
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 RFC 2060                       IMAP4rev1                   December 1996
 
 
 25) Add a clarification that external changes to flags should be
 always announced via an untagged FETCH even if the current command is
 a STORE with the ".SILENT" suffix.
 
 26) Add a clarification that COPY appends to the target mailbox.
 
 27) Add the NEWNAME response code.
 
 28) Rewrite the description of the untagged BYE response to clarify
 its semantics.
 
 29) Change the reference for the body MD5 to refer to the proper RFC.
 
 30) Clarify that the formal syntax contains rules which may overlap,
 and that in the event of such an overlap the rule which occurs first
 takes precedence.
 
 31) Correct the definition of body_fld_param.
 
 32) More formal syntax for capability_data.
 
 33) Clarify that any case variant of "INBOX" must be interpreted as
 INBOX.
 
 34) Clarify that the human-readable text in resp_text should not
 begin with "[" or "=".
 
 35) Change MIME references to Draft Standard documents.
 
 36) Clarify \Recent semantics.
 
 37) Additional examples.
 
 C.      Key Word Index
 
        +FLAGS <flag list> (store command data item) ...............   45
        +FLAGS.SILENT <flag list> (store command data item) ........   46
        -FLAGS <flag list> (store command data item) ...............   46
        -FLAGS.SILENT <flag list> (store command data item) ........   46
        ALERT (response code) ......................................   50
        ALL (fetch item) ...........................................   41
        ALL (search key) ...........................................   38
        ANSWERED (search key) ......................................   38
        APPEND (command) ...........................................   34
        AUTHENTICATE (command) .....................................   20
        BAD (response) .............................................   52
        BCC <string> (search key) ..................................   38
        BEFORE <date> (search key) .................................   39
 
 
 
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        BODY (fetch item) ..........................................   41
        BODY (fetch result) ........................................   58
        BODY <string> (search key) .................................   39
        BODY.PEEK[<section>]<<partial>> (fetch item) ...............   44
        BODYSTRUCTURE (fetch item) .................................   44
        BODYSTRUCTURE (fetch result) ...............................   59
        BODY[<section>]<<origin_octet>> (fetch result) .............   58
        BODY[<section>]<<partial>> (fetch item) ....................   41
        BYE (response) .............................................   52
        Body Structure (message attribute) .........................   11
        CAPABILITY (command) .......................................   18
        CAPABILITY (response) ......................................   53
        CC <string> (search key) ...................................   39
        CHECK (command) ............................................   36
        CLOSE (command) ............................................   36
        COPY (command) .............................................   46
        CREATE (command) ...........................................   25
        DELETE (command) ...........................................   26
        DELETED (search key) .......................................   39
        DRAFT (search key) .........................................   39
        ENVELOPE (fetch item) ......................................   44
        ENVELOPE (fetch result) ....................................   62
        EXAMINE (command) ..........................................   24
        EXISTS (response) ..........................................   56
        EXPUNGE (command) ..........................................   37
        EXPUNGE (response) .........................................   57
        Envelope Structure (message attribute) .....................   11
        FAST (fetch item) ..........................................   44
        FETCH (command) ............................................   41
        FETCH (response) ...........................................   58
        FLAGGED (search key) .......................................   39
        FLAGS (fetch item) .........................................   44
        FLAGS (fetch result) .......................................   62
        FLAGS (response) ...........................................   56
        FLAGS <flag list> (store command data item) ................   45
        FLAGS.SILENT <flag list> (store command data item) .........   45
        FROM <string> (search key) .................................   39
        FULL (fetch item) ..........................................   44
        Flags (message attribute) ..................................    9
        HEADER (part specifier) ....................................   41
        HEADER <field-name> <string> (search key) ..................   39
        HEADER.FIELDS <header_list> (part specifier) ...............   41
        HEADER.FIELDS.NOT <header_list> (part specifier) ...........   41
        INTERNALDATE (fetch item) ..................................   44
        INTERNALDATE (fetch result) ................................   62
        Internal Date (message attribute) ..........................   10
        KEYWORD <flag> (search key) ................................   39
        Keyword (type of flag) .....................................   10
 
 
 
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        LARGER <n> (search key) ....................................   39
        LIST (command) .............................................   30
        LIST (response) ............................................   54
        LOGIN (command) ............................................   22
        LOGOUT (command) ...........................................   20
        LSUB (command) .............................................   32
        LSUB (response) ............................................   55
        MAY (specification requirement term) .......................    5
        MESSAGES (status item) .....................................   33
        MIME (part specifier) ......................................   42
        MUST (specification requirement term) ......................    4
        MUST NOT (specification requirement term) ..................    4
        Message Sequence Number (message attribute) ................    9
        NEW (search key) ...........................................   39
        NEWNAME (response code) ....................................   50
        NO (response) ..............................................   51
        NOOP (command) .............................................   19
        NOT <search-key> (search key) ..............................   39
        OK (response) ..............................................   51
        OLD (search key) ...........................................   39
        ON <date> (search key) .....................................   39
        OPTIONAL (specification requirement term) ..................    5
        OR <search-key1> <search-key2> (search key) ................   39
        PARSE (response code) ......................................   50
        PERMANENTFLAGS (response code) .............................   50
        PREAUTH (response) .........................................   52
        Permanent Flag (class of flag) .............................   10
        READ-ONLY (response code) ..................................   50
        READ-WRITE (response code) .................................   50
        RECENT (response) ..........................................   57
        RECENT (search key) ........................................   39
        RECENT (status item) .......................................   33
        RENAME (command) ...........................................   27
        REQUIRED (specification requirement term) ..................    4
        RFC822 (fetch item) ........................................   44
        RFC822 (fetch result) ......................................   63
        RFC822.HEADER (fetch item) .................................   44
        RFC822.HEADER (fetch result) ...............................   62
        RFC822.SIZE (fetch item) ...................................   44
        RFC822.SIZE (fetch result) .................................   62
        RFC822.TEXT (fetch item) ...................................   44
        RFC822.TEXT (fetch result) .................................   62
        SEARCH (command) ...........................................   37
        SEARCH (response) ..........................................   55
        SEEN (search key) ..........................................   40
        SELECT (command) ...........................................   23
        SENTBEFORE <date> (search key) .............................   40
        SENTON <date> (search key) .................................   40
 
 
 
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        SENTSINCE <date> (search key) ..............................   40
        SHOULD (specification requirement term) ....................    5
        SHOULD NOT (specification requirement term) ................    5
        SINCE <date> (search key) ..................................   40
        SMALLER <n> (search key) ...................................   40
        STATUS (command) ...........................................   33
        STATUS (response) ..........................................   55
        STORE (command) ............................................   45
        SUBJECT <string> (search key) ..............................   40
        SUBSCRIBE (command) ........................................   29
        Session Flag (class of flag) ...............................   10
        System Flag (type of flag) .................................    9
        TEXT (part specifier) ......................................   42
        TEXT <string> (search key) .................................   40
        TO <string> (search key) ...................................   40
        TRYCREATE (response code) ..................................   51
        UID (command) ..............................................   47
        UID (fetch item) ...........................................   44
        UID (fetch result) .........................................   63
        UID <message set> (search key) .............................   40
        UIDNEXT (status item) ......................................   33
        UIDVALIDITY (response code) ................................   51
        UIDVALIDITY (status item) ..................................   34
        UNANSWERED (search key) ....................................   40
        UNDELETED (search key) .....................................   40
        UNDRAFT (search key) .......................................   40
        UNFLAGGED (search key) .....................................   40
        UNKEYWORD <flag> (search key) ..............................   40
        UNSEEN (response code) .....................................   51
        UNSEEN (search key) ........................................   40
        UNSEEN (status item) .......................................   34
        UNSUBSCRIBE (command) ......................................   30
        Unique Identifier (UID) (message attribute) ................    7
        X<atom> (command) ..........................................   48
        [RFC-822] Size (message attribute) .........................   11
        \Answered (system flag) ....................................    9
        \Deleted (system flag) .....................................    9
        \Draft (system flag) .......................................    9
        \Flagged (system flag) .....................................    9
        \Marked (mailbox name attribute) ...........................   54
        \Noinferiors (mailbox name attribute) ......................   54
        \Noselect (mailbox name attribute) .........................   54
        \Recent (system flag) ......................................   10
        \Seen (system flag) ........................................    9
        \Unmarked (mailbox name attribute) .........................   54
 
 
 
 
 
 
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