< draft-crispin-imapv-19.txt		draft-crispin-imapv-20.txt >
			A new Request for Comments is now available in online RFC libraries.
	Network Working Group M. Crispin		RFC 3501
	INTERNET-DRAFT: IMAP4rev1 University of Washington
	Obsoletes: 2060 September 2002
	Document: internet-drafts/draft-crispin-imapv-19.txt
	INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
	Status of this Memo
	This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC 2026.
	This document is an Internet-Draft. Internet-Drafts are working
	documents of the Internet Engineering Task Force (IETF), its areas,
	and its working groups. Note that other groups may also distribute
	working documents as Internet-Drafts.
	Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."
	To view the list Internet-Draft Shadow Directories, see
	http://www.ietf.org/shadow.html.
	A revised version of this draft document will be submitted to the RFC
	editor as an Proposed Standard for the Internet Community.
	Discussion and suggestions for improvement are requested, and should
	be sent to imap@CAC.Washington.EDU. This document will expire before
	25 March 2003. Distribution of this memo is unlimited.
	This document is a revision of RFC 2060. Appendix B of this document
	describes revisions and changes.
	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 mailboxes (remote
	message folders) in a way that is functionally equivalent to local
	folders. 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-2822] 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 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
	"Conventions" are basic principles or procedures. Document
	conventions are noted in this section.
	In examples, "C:" and "S:" indicate lines sent by the client and
	server respectively.
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "MAY", and "OPTIONAL" in this document are to
	be interpreted as described in [KEYWORDS].
	The word "can" (not "may") is used to refer to a possible
	circumstance or situation, as opposed to an optional facility of the
	protocol.
	"User" is used to refer to a human user, whereas "client" refers to
	the software being run by the user.
	"Connection" refers to the entire sequence of client/server
	interaction from the initial establishment of the network connection
	until its termination. "Session" refers to the sequence of
	client/server interaction from the time that a mailbox is selected
	(SELECT or EXAMINE command) until the time that selection ends
	(SELECT or EXAMINE of another mailbox, CLOSE command, or connection
	termination).
	Characters are 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.
	There are several protocol conventions in IMAP. These refer to
	aspects of the specification which are not strictly part of the IMAP
	protocol, but which reflect generally-accepted practice.
	Implementations need to be aware of these conventions, and avoid
	conflicts whether or not they implement the convention. For example,
	"&" may not be used as a hierarchy delimiter since it conflicts with
	the Mailbox International Naming Convention, and other uses of "&" in
	mailbox names are impacted as well.
	1.3. Special Notes to Implementors
	Implementors of the IMAP protocol are strongly encouraged to read the
	IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in
	conjunction with this document, to help understand the intricacies of
	this protocol and how best to build an interoperable product.
	IMAP4rev1 is designed to be upwards compatible from the [IMAP2] and
	unpublished IMAP2bis protocols. IMAP4rev1 is largely compatible with
	the IMAP4 protocol described in RFC 1730; the exception being in
	certain facilities added in RFC 1730 that proved problematic and were
	subsequently removed. In the course of the evolution of IMAP4rev1,
	some aspects in the earlier protocols have become obsolete. Obsolete
	commands, responses, and data formats which an IMAP4rev1
	implementation can encounter when used with an earlier implementation
	are described in [IMAP-OBSOLETE].
	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.
	IMAP was originally developed for the older [RFC-822] standard, and
	as a consequence several fetch items in IMAP incorporate "RFC822" in
	their name. With the exception of RFC822.SIZE, there are more modern
	replacements; for example, the modern version of RFC822.HEADER is
	BODY[HEADER.PEEK]. In all cases, "RFC822" should be interpreted as a
	reference to the updated [RFC-2822] standard.
	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.
	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.
	Clients MUST follow the syntax outlined in this specification
	strictly. It is a syntax error to send a command with missing or
	extraneous spaces or arguments.
	There are two cases in which a line from the client does not
	represent a complete command. In one case, a command argument is
	quoted with an octet count (see the description of literal in String
	under Data Formats); in the other case, the command arguments require
	server feedback (see the AUTHENTICATE command). In either case, the
	server sends a command continuation request response if it is ready
	for the octets (if appropriate) and the remainder of the command.
	This response is prefixed with the token "+".
	Note: If, instead, the server detected an error in the
	command, it sends a BAD completion response with 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.
	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).
	Servers SHOULD enforce the syntax outlined in this specification
	strictly. Any client command with a protocol syntax error, including
	(but not limited to) missing or extraneous spaces or arguments,
	SHOULD be rejected, and the client given a BAD server completion
	response.
	The protocol receiver of an 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 can 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
	that MUST NOT refer to any other message in the mailbox or any
	subsequent mailbox with the same name forever. Unique identifiers
	are assigned in a strictly ascending fashion in the mailbox; as each
	message is added to the mailbox it is assigned a higher UID than the
	message(s) which were added previously. Unlike message sequence
	numbers, unique identifiers are not necessarily contiguous.
	The unique identifier of a message MUST NOT change during the
	session, and SHOULD NOT change between sessions. Any change of
	unique identifiers between sessions MUST be detectable using the
	UIDVALIDITY mechanism discussed below. Persistent unique identifiers
	are required for a client to resynchronize its state from a previous
	session with the server (e.g. disconnected or offline access
	clients); this is discussed further in [IMAP-DISC].
	Associated with every mailbox are two values which aid in unique
	identifier handling: the next unique identifier value and the unique
	identifier validity value.
	The next unique identifier value is the predicted value that will be
	assigned to a new message in the mailbox. Unless the unique
	identifier validity also changes (see below), the next unique
	identifier value MUST have the following two characteristics. First,
	the next unique identifier value MUST NOT change unless new messages
	are added to the mailbox; and second, the next unique identifier
	value MUST change whenever new messages are added to the mailbox,
	even if those new messages are subsequently expunged.
	Note: The next unique identifier value is intended to
	provide a means for a client to determine whether any
	messages have been delivered to the mailbox since the
	previous time it checked this value. It is not intended to
	provide any guarantee that any message will have this
	unique identifier; a client can only assume that a new
	message will have a UID that is greater than or equal to
	the next unique identifier value.
	The unique identifier validity value 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: Ideally, unique identifiers SHOULD persist at all
	times. Although this specification recognizes that failure
	to persist can be unavoidable in certain server
	environments, it STRONGLY ENCOURAGES message store
	implementation techniques that avoid this problem. For
	example:
	1) 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 identifiers are no longer strictly ascending
	as a result of the re-ordering.
	2) If the message store has no mechanism to store unique
	identifiers, it must regenerate unique identifiers at each
	session, and each session must have a unique UIDVALIDITY
	value.
	3) If the mailbox is deleted and a new mailbox with the
	same name is created at a later date, the server must
	either keep track of unique identifiers from the previous
	instance of the mailbox, or it must assign a new
	UIDVALIDITY value to the new instance of the mailbox. A
	good UIDVALIDITY value to use in this case is a 32-bit
	representation of the creation date/time of the mailbox.
	It is alright to use a constant such as 1, but only if it
	guaranteed that unique identifiers will never be reused,
	even in the case of a mailbox being deleted (or renamed)
	and a new mailbox by the same name created at some future
	time.
	4) The combination of mailbox name, UIDVALIDITY, and UID
	must refer to a single immutable message on that server
	forever. In particular, the internal date, [RFC-2822]
	size, envelope, body structure, and message texts (RFC822,
	RFC822.HEADER, RFC822.TEXT, and all BODY[...] fetch data
	items) must never change. This does not include message
	numbers, nor does it include attributes that can be set by
	a STORE command (e.g. FLAGS).
	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. The number of messages in the mailbox is also
	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 "11 EXISTS" is received,
	and previously an untagged "8 EXISTS" was received, three new
	messages have arrived with message sequence numbers of 9, 10, and 11.
	Another example; if message 287 in a 523 message mailbox has UID
	12345, there are exactly 286 messages which have lesser UIDs and 236
	messages which have greater UIDs.
	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 can be permanent or session-only.
	A system flag is a flag name that is pre-defined in this
	specification. All system flags begin with "\". Certain system
	flags (\Deleted and \Seen) have special semantics described
	elsewhere. The currently-defined system flags are:
	\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).
	\Recent
	Message is "recently" arrived in this mailbox. This session
	is the first session to have been notified about this
	message; if the session is read-write, 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-arrived 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 can be permanent or session-only on a per-flag basis.
	Permanent flags are those which the client can add or remove from the
	message flags permanently; that is, 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-2822] 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.
	2.3.4. [RFC-2822] Size Message Attribute
	The number of octets in the message, as expressed in [RFC-2822]
	format.
	2.3.5. Envelope Structure Message Attribute
	A parsed representation of the [RFC-2822] header of the message.
	Note that the IMAP Envelope structure is not the same as an [SMTP]
	envelope.
	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-2822] text of a
	message, IMAP4rev1 permits the fetching of portions of the full
	message text. Specifically, it is possible to fetch the [RFC-2822]
	message header, [RFC-2822] message body, a [MIME-IMB] body part, or a
	[MIME-IMB] header.
	3. State and Flow Diagram
	Once the connection between client and server is established, an
	IMAP4rev1 connection is in one of four states. The initial state is
	identified in the server greeting. Most commands are only valid in
	certain states. It is a protocol error for the client to attempt a
	command while the connection is in an inappropriate state, and the
	server will respond with a BAD or NO (depending upon server
	implementation) command completion result.
	3.1. Not Authenticated State
	In not authenticated state, the client MUST supply authentication
	credentials before most commands will be permitted. This state is
	entered when a connection starts unless the connection has been
	pre-authenticated.
	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.
	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. This state can
	be entered as a result of a client request (via the LOGOUT command)
	or by unilateral action on the part of either the client or server.
	If the client requests logout state, the server MUST send an untagged
	BYE response and a tagged OK response to the LOGOUT command before
	the server closes the connection; and the client MUST read the tagged
	OK response to the LOGOUT command before the client closes the
	connection.
	A server MUST NOT unilaterally close the connection without sending
	an untagged BYE response that contains the reason for having done so.
	A client SHOULD NOT unilaterally close the connection, and instead
	SHOULD issue a LOGOUT command. If the server detects that the client
	has unilaterally closed the connection, the server MAY omit the
	untagged BYE response and simply close its connection.
	+----------------------+
	|connection established|
	+----------------------+
	||
	\/
	+--------------------------------------+
	| server greeting |
	+--------------------------------------+
	|| (1) || (2) || (3)
	\/ || ||
	+-----------------+ || ||
	|Not Authenticated| || ||
	+-----------------+ || ||
	|| (7) || (4) || ||
	|| \/ \/ ||
	|| +----------------+ ||
	|| | Authenticated |<=++ ||
	|| +----------------+ || ||
	|| || (7) || (5) || (6) ||
	|| || \/ || ||
	|| || +--------+ || ||
	|| || |Selected|==++ ||
	|| || +--------+ ||
	|| || || (7) ||
	\/ \/ \/ \/
	+--------------------------------------+
	| Logout |
	+--------------------------------------+
	||
	\/
	+-------------------------------+
	|both sides close the connection|
	+-------------------------------+
	(1) connection without pre-authentication (OK greeting)
	(2) pre-authenticated connection (PREAUTH greeting)
	(3) rejected connection (BYE greeting)
	(4) successful 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. Note that a particular data item may take more than one
	form; for example, a data item defined as using "astring" syntax may
	be either an atom or a string.
	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: either literal or quoted string.
	The literal form is the general form of string. The quoted string
	form is an alternative that avoids the overhead of processing a
	literal at the cost of limitations of characters which may be used.
	A literal is a sequence of zero or more octets (including CR and LF),
	prefix-quoted with an octet count in the form of an open brace ("{"),
	the number of octets, close brace ("}"), and CRLF. In the case of
	literals transmitted from server to client, the CRLF is immediately
	followed by the octet data. In the case of literals transmitted from
	client to server, the client MUST wait to receive a command
	continuation request (described later in this document) before
	sending the octet data (and the remainder of the command).
	A quoted string is a sequence of zero or more 7-bit characters,
	excluding CR and LF, with double quote (<">) characters at each end.
	The empty string is represented as either "" (a quoted string with
	zero characters between double quotes) or as {0} followed by CRLF (a
	literal with an octet count of 0).
	Note: Even if the octet count is 0, a client transmitting a
	literal MUST wait to receive a command continuation
	request.
	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.
	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 form "NIL" represents the non-existence of a particular
	data item that is represented as a string or parenthesized list, as
	distinct from the empty string "" or the empty parenthesized list ().
	Note: NIL is never used for any data item which takes the
	form of an atom. For example, a mailbox name of "NIL" is a
	mailbox named NIL as opposed to a non-existant mailbox
	name. This is because mailbox uses "astring" syntax which
	is an atom or a string. Conversely, an addr-name of NIL is
	a non-existant personal name, because addr-name uses
	"nstring" syntax which is NIL or a string, but never an
	atom.
	5. Operational Considerations
	The following rules are listed here to ensure that all IMAP4rev1
	implementations interoperate properly.
	5.1. Mailbox Naming
	Mailbox names are 7-bit. Client implementations MUST NOT attempt to
	create 8-bit mailbox names, and SHOULD interpret any 8-bit mailbox
	names returned by LIST or LSUB as UTF-8. Server implementations
	SHOULD prohibit the creation of 8-bit mailbox names, and SHOULD NOT
	return 8-bit mailbox names in LIST or LSUB. See section 5.1.3 for
	more information on how to represent non-ASCII mailbox names.
	Note: 8-bit mailbox names were undefined in earlier
	versions of this protocol. Some sites used a local 8-bit
	character set to represent non-ASCII mailbox names. Such
	usage is not interoperable, and is now formally deprecated.
	The case-insensitive mailbox name INBOX is a special name reserved to
	mean "the primary mailbox for this user on this server". The
	interpretation of all other names is implementation-dependent.
	In particular, this specification takes no position on case
	sensitivity in non-INBOX mailbox names. Some server implementations
	are fully case-sensitive; others preserve case of a newly-created
	name but otherwise are case-insensitive; and yet others coerce names
	to a particular case. Client implementations MUST interact with any
	of these. If a server implementation interprets non-INBOX mailbox
	names as case-insensitive, it MUST treat names using the
	international naming convention specially as described in section
	5.1.3.
	There are certain client considerations when creating a new mailbox
	name:
	1) Any character which is one of the atom-specials (see the Formal
	Syntax) will require that the mailbox name be represented as a
	quoted string or literal.
	2) CTL and other non-graphic characters are difficult to represent
	in a user interface and are best avoided.
	3) Although the list-wildcard characters ("%" and "*") are valid
	in a mailbox name, it is difficult to use such mailbox names
	with the LIST and LSUB commands due to the conflict with
	wildcard interpretation.
	4) Usually, a character (determined by the server implementation)
	is reserved to delimit levels of hierarchy.
	5) Two characters, "#" and "&", have meanings by convention, and
	should be avoided except when used in that convention.
	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.
	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" can refer to a different object (e.g. a
	user's private mailbox).
	5.1.3. Mailbox International Naming Convention
	By convention, international mailbox names in IMAP4rev1 are specified
	using a modified version of the UTF-7 encoding described in [UTF-7].
	Modified UTF-7 may also be usable in servers which implement an
	earlier version of this protocol.
	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 and 0x7f-0xff) 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. There is no implicit shift from BASE64 to US-ASCII, and
	null shifts ("-&" while in BASE64; note that "&-" while in US-ASCII
	means "&") are not permitted. However, all names start in US-ASCII,
	and MUST end in US-ASCII; that is, a name that ends with a non-ASCII
	ISO-10646 character MUST end with a "-").
	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 characters can be
	represented in encoded form.
	Although modified UTF-7 is a convention, it establishes certain
	requirements on server handling of any mailbox name with an
	embedded "&" character. In particular, server implementations
	MUST preserve the exact form of the modified BASE64 portion of a
	modified UTF-7 name and treat that text as case-sensitive, even if
	names are otherwise case-insensitive or case-folded.
	Server implementations SHOULD verify that any mailbox name
	argument to CREATE with an embedded "&" character is in correct
	modified UTF-7 syntax; that there are no superfluous shifts; and
	that there is no encoding in modified BASE64 of any printing
	US-ASCII character which can represent itself. However, client
	implementations MUST NOT depend upon the server doing this; and
	SHOULD NOT attempt to create a mailbox name with an embedded "&"
	character unless it complies with modified UTF-7 syntax.
	Server implementations which export a mail store which does not
	follow the modified UTF-7 convention MUST convert to modified
	UTF-7 any mailbox name that contains either non-ASCII characters
	or the "&" character.
	For example, here is a mailbox name which mixes English,
	Chinese, and Japanese text:
	~peter/mail/&U,BTFw-/&ZeVnLIqe-
	For example, the string "&Jjo!" is not a valid mailbox
	name because it does not contain a shift to US-ASCII
	before the "!". The correct form is "&Jjo-!". The
	string "&U,BTFw-&ZeVnLIqe-" is not permitted because it
	contains a superfluous shift. The correct form is
	"&U,BTF2XlZyyKng-".
	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 message
	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. In particular,
	it is NOT permitted to send an EXISTS response that would reduce the
	number of messages in the mailbox; only the EXPUNGE response can do
	this.
	Regardless of what implementation decisions a client makes on
	remembering data from the server, a client implementation MUST record
	mailbox size updates. It MUST NOT assume that any command after
	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, the duration of that
	timer MUST be at least 30 minutes. The receipt of ANY command from
	the client during that interval SHOULD suffice to reset the
	autologout timer.
	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 the completion result response before sending a command
	with message sequence numbers.
	Note: UID FETCH, UID STORE, and UID SEARCH are different
	commands from FETCH, STORE, and SEARCH. If the client
	sends a UID command, it must wait for a completion result
	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
	UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting
	command sequence, depending upon whether or not the second UID
	SEARCH contains message sequence numbers.
	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
	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.
	The state of a connection is only changed by successful commands
	which are documented as changing state. In particular, a failed (NO
	response) or rejected (BAD response) command does not change the
	state of the connection.
	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.
	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.
	Client and server implementations MUST implement the STARTTLS,
	LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
	capabilities. See the Security Considerations section for
	important information.
	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 STARTTLS AUTH=GSSAPI
	LOGINDISABLED
	S: abcd OK CAPABILITY completed
	C: efgh STARTTLS
	S: efgh OK STARTLS completed
	<TLS negotiation, further commands are under [TLS] layer>
	C: ijkl CAPABILITY
	S: * CAPABILITY IMAP4rev1 AUTH=GSSAPI AUTH=PLAIN
	S: ijkl 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 (this is the
	preferred method to do this). 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
	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 - Not Authenticated State
	In not authenticated state, the AUTHENTICATE or LOGIN command
	establishes authentication and enters authenticated state. The
	AUTHENTICATE command provides a general mechanism for a variety of
	authentication techniques, privacy protection, and integrity
	checking; whereas the LOGIN command uses a traditional user name and
	plaintext password pair and has no means of establishing privacy
	protection or integrity checking.
	The STARTTLS command is an alternate form of establishing session
	privacy protection and integrity checking, but does not establish
	authentication or enter authenticated state.
	Server implementations MAY allow access to certain mailboxes without
	establishing authentication. This can be done by means of the
	ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older
	convention is a LOGIN command using the userid "anonymous"; in this
	case a password is required although the server may choose to accept
	any password. It is implementation-dependent what restrictions are
	placed on anonymous users.
	Once authenticated (including as anonymous), it is not possible to
	re-enter not authenticated state.
	In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
	the following commands are valid in not authenticated state:
	STARTTLS, AUTHENTICATE and LOGIN. See the Security Considerations
	section for important information about these commands.
	6.2.1. STARTTLS Command
	Arguments: none
	Responses: no specific response for this command
	Result: OK - starttls completed, begin TLS negotiation
	BAD - command unknown or arguments invalid
	A [TLS] negotiation begins immediately after the CRLF at the end
	of the tagged OK response from the server. Once a client issues a
	STARTTLS command, it MUST NOT issue further commands until a
	server response is seen and the [TLS] negotiation is complete.
	The server remains in non-authenticated state, even if client
	credentials are supplied during the [TLS] negotiation. This does
	not preclude an authentication mechanism such as EXTERNAL (defined
	in [SASL]) from using client identity determined by the [TLS]
	negotiation.
	Once [TLS] has been started, the client MUST discard cached
	information about server capabilities and SHOULD re-issue the
	CAPABILITY command. This is necessary to protect against man-in-
	the-middle attacks which alter the capabilities list prior to
	STARTTLS. The server MAY advertise different capabilities after
	STARTTLS.
	Example: C: a001 CAPABILITY
	S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
	S: a001 OK CAPABILITY completed
	C: a002 STARTTLS
	S: a002 OK Begin TLS negotiation now
	<TLS negotiation, further commands are under [TLS] layer>
	C: a003 CAPABILITY
	S: * CAPABILITY IMAP4rev1 AUTH=PLAIN
	S: a003 OK CAPABILITY completed
	C: a004 LOGIN joe password
	S: a004 OK LOGIN completed
	6.2.2. AUTHENTICATE Command
	Arguments: authentication mechanism name
	Responses: continuation data can be requested
	Result: OK - authenticate completed, now in authenticated state
	NO - authenticate failure: unsupported authentication
	mechanism, credentials rejected
	BAD - command unknown or arguments invalid,
	authentication exchange cancelled
	The AUTHENTICATE command indicates a [SASL] authentication
	mechanism to the server. If the server supports the requested
	authentication mechanism, it performs an authentication protocol
	exchange to authenticate and identify the client. It MAY also
	negotiate an OPTIONAL security layer for subsequent protocol
	interactions. If the requested authentication mechanism is not
	supported, the server SHOULD reject the AUTHENTICATE command by
	sending a tagged NO response.
	The AUTHENTICATE command does not support the optional "initial
	response" feature of [SASL]. Section 5.1 of [SASL] specifies how
	to handle an authentication mechanism which uses an initial
	response.
	The service name specified by this protocol's profile of [SASL] is
	"imap".
	The authentication protocol exchange consists of a series of
	server challenges and client responses that are specific to the
	authentication mechanism. A server challenge consists of a
	command continuation request response with the "+" token followed
	by a BASE64 encoded string. The client response consists of a
	single line consisting of a BASE64 encoded string. If the client
	wishes to cancel an authentication exchange, it issues a line
	consisting of a single "*". If the server receives such an
	response, it MUST reject the AUTHENTICATE command by sending a
	tagged BAD response.
	If a security layer is negotiated through the [SASL]
	authentication exchange, it takes effect immediately following the
	CRLF that concludes the authentication exchange for the client,
	and the CRLF of the tagged OK response for the server.
	While client and server implementations MUST implement the
	AUTHENTICATE command itself, it is not required to implement any
	authentication mechanisms other than the PLAIN mechanism described
	in [IMAP-TLS]. Also, an authentication mechanism is not required
	to support any security layers.
	Note: a server implementation MUST implement a
	configuration in which it does NOT permit any plaintext
	password mechanisms, unless either the STARTTLS command
	has been negotiated or some other mechanism that
	protects the session from password snooping has been
	provided. Server sites SHOULD NOT use any configuration
	which permits a plaintext password mechanism without
	such a protection mechanism against password snooping.
	Client and server implementations SHOULD implement
	additional [SASL] mechanisms which do not use plaintext
	passwords, such the GSSAPI mechanism described in [SASL]
	and/or the [DIGEST-MD5] mechanism.
	Servers and clients can support multiple authentication
	mechanisms. The server SHOULD list its supported authentication
	mechanisms in the response to the CAPABILITY command so that the
	client knows which authentication mechanisms to use.
	A server MAY include a CAPABILITY response code in the tagged OK
	response of a successful AUTHENTICATE command in order to send
	capabilities automatically. It is unnecessary for a client to
	send a separate CAPABILITY command if it recognizes these
	automatic capabilities. This should only be done if a security
	layer was not negotiated by the AUTHENTICATE command, because the
	tagged OK response as part of an AUTHENTICATE command is not
	protected by encryption/integrity checking. [SASL] requires the
	client to re-issue a CAPABILITY command in this case.
	If an AUTHENTICATE command fails with a NO response, the client
	MAY try another authentication mechanism by issuing another
	AUTHENTICATE command. It MAY also attempt to authenticate by
	using the LOGIN command (see section 6.2.3 for more detail). In
	other words, the client MAY request authentication types in
	decreasing order of preference, with the LOGIN command as a last
	resort.
	The authorization identity passed from the client to the server
	during the authentication exchange is interpreted by the server as
	the user name whose privileges the client is requesting.
	Example: S: * OK IMAP4rev1 Server
	C: A001 AUTHENTICATE GSSAPI
	S: +
	C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw
	MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0
	b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW
	Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA
	cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX
	AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y
	C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb
	I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi
	vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL
	pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n
	FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE
	NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx
	O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB
	vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg==
	S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC
	AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0
	uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg==
	C:
	S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe
	ceP2CWY0SR0fAQAgAAQEBAQ=
	C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP
	wkhbfa2QteAQAgAG1yYwE=
	S: A001 OK GSSAPI authentication successful
	Note: The line breaks in the first client response are for
	editorial clarity and are not in real authenticators.
	6.2.3. 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.
	A server MAY include a CAPABILITY response code in the tagged OK
	response to a successful LOGIN command in order to send
	capabilities automatically. It is unnecessary for a client to
	send a separate CAPABILITY command if it recognizes these
	automatic capabilities.
	Example: C: a001 LOGIN SMITH SESAME
	S: a001 OK LOGIN completed
	Note: Use of the LOGIN command over an insecure network
	(such as the Internet) is a security risk, because anyone
	monitoring network traffic can obtain plaintext passwords.
	The LOGIN command SHOULD NOT be used except as a last
	resort, and it is recommended that client implementations
	have a means to disable any automatic use of the LOGIN
	command.
	A server implementation MUST implement a configuration in
	which, unless either the STARTTLS command has been
	negotiated or some other mechanism that protects the
	session from password snooping has been provided, it
	advertises the LOGINDISABLED capability and does NOT permit
	the LOGIN command. Server sites SHOULD NOT use any
	configuration which permits the LOGIN command without such
	a protection mechanism against password snooping. A client
	implementation MUST NOT send a LOGIN command if the
	LOGINDISABLED capability is advertised.
	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.
	6.3.1. SELECT Command
	Arguments: mailbox name
	Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
	REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
	UIDNEXT, UIDVALIDITY
	Result: OK - select completed, now in selected state
	NO - select failure, now in authenticated state: no
	such mailbox, can't access mailbox
	BAD - command unknown or arguments invalid
	The SELECT command selects a mailbox so that messages in the
	mailbox can be accessed. Before returning an OK to the client,
	the server MUST send the following untagged data to the client.
	Note that earlier versions of this protocol only required the
	FLAGS, EXISTS, and RECENT untagged data; consequently, client
	implementations SHOULD implement default behavior for missing data
	as discussed with the individual item.
	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 [UNSEEN <n>]
	The message sequence number of the first unseen
	message in the mailbox. If this is missing, the
	client can not make any assumptions about the first
	unseen message in the mailbox, and needs to issue a
	SEARCH command if it wants to find it.
	OK [PERMANENTFLAGS (<list of flags>)]
	A list of message flags that the client can change
	permanently. If this is missing, the client should
	assume that all flags can be changed permanently.
	OK [UIDNEXT <n>]
	The next unique identifier value. Refer to section
	2.3.1.1 for more information. If this is missing,
	the client can not make any assumptions about the
	next unique identifier value.
	OK [UIDVALIDITY <n>]
	The unique identifier validity value. Refer to
	section 2.3.1.1 for more information. If this is
	missing, the server does not support unique
	identifiers.
	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.
	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: * OK [UIDNEXT 4392] Predicted next UID
	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
	REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
	UIDNEXT, UIDVALIDITY
	Result: OK - examine completed, now in selected state
	NO - examine failure, now in authenticated state: no
	such mailbox, can't access mailbox
	BAD - command unknown or arguments invalid
	The EXAMINE command is identical to SELECT and returns the same
	output; however, the selected mailbox is identified as read-only.
	No changes to the permanent state of the mailbox, including
	per-user state, are permitted; in particular, EXAMINE MUST NOT
	cause messages to lose the \Recent flag.
	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: * OK [UIDNEXT 4392] Predicted next UID
	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
	the declaration. In any case, the name that is created is the
	name without the trailing hierarchy delimiter.
	If the server's hierarchy separator character appears elsewhere in
	the name, the server SHOULD create any superior hierarchical names
	that are needed for the CREATE command to 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.
	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.
	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
	an error to attempt to rename from a mailbox name that does not
	exist or to a mailbox name that already exists. Any error in
	renaming will return a tagged NO response.
	If the name has inferior hierarchical names, then the inferior
	hierarchical names MUST also be renamed. For example, a rename of
	"foo" to "zap" will rename "foo/bar" (assuming "/" is the
	hierarchy delimiter character) to "zap/bar".
	If the server's hierarchy separator character appears in the name,
	the server SHOULD create any superior hierarchical names that are
	needed for the RENAME command to complete successfully. In other
	words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a
	server in which "/" is the hierarchy separator character SHOULD
	create baz/ and baz/rag/ if they do not already exist.
	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
	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 a server site can
	choose to routinely remove a mailbox with a well-known
	name (e.g. "system-alerts") after its contents expire,
	with the intention of recreating it when new contents
	are appropriate.
	Example: C: A002 SUBSCRIBE #news.comp.mail.mime
	S: A002 OK SUBSCRIBE completed
	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 the context in which the mailbox
	name is interpreted.
	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 the empty
	string if the reference is non-rooted or is the empty string. In
	all cases, a hierarchy delimiter (or NIL if there is no hierarchy)
	is returned. This permits a client to get the hierarchy delimiter
	(or find out that the mailbox names are flat) even when no
	mailboxes by that name currently exist.
	The reference and mailbox name arguments are interpreted into a
	canonical form that represents an unambiguous left-to-right
	hierarchy. The returned mailbox names will be in the interpreted
	form.
	Note: The interpretation of the reference argument is
	implementation-defined. It depends upon whether the
	server implementation has a concept of "current working
	directory" and leading "break out characters" which
	override the current working directory.
	For example, on a server which exports a UNIX or NT
	filesystems, the reference argument contains the current
	working directory and the mailbox name argument would
	contain the name as interpreted in the current working
	directory.
	If a server implementation has no concept of break out
	characters, the canonical form is normally the reference
	name appended with the mailbox name. Note that if the
	server implements the namespace convention (section
	5.1.2), "#" is a break out character and must be treated
	as such.
	If the reference argument is not a level of mailbox
	hierarchy (that is, it is a \NoInferiors name), and/or
	the reference argument does not end with the hierarchy
	delimiter, it is implementation-dependent how this is
	interpreted. For example, a reference of "foo/bar" and
	mailbox name of "rag/baz" could be interpreted as
	"foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/baz".
	A client SHOULD NOT use such a reference argument except
	at the explicit request of the user. A hierarchical
	browser MUST NOT make any assumptions about server
	interpretation of the reference unless the reference is
	a level of mailbox hierarchy AND ends with the hierarchy
	delimiter.
	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).
	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.
	The returned untagged LSUB response MAY contain different mailbox
	flags from a LIST untagged response. If this should happen, the
	flags in the untagged LIST are considered more authoritative.
	A special situation occurs when using LSUB with the % wildcard.
	Consider what happens if "foo/bar" (with a hierarchy delimiter of
	"/") is subscribed but "foo" is not. A "%" wildcard to LSUB must
	return foo, not foo/bar, in the LSUB response, and it MUST be
	flagged with the \Noselect attribute.
	The server MUST NOT 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
	C: A003 LSUB "#news." "comp.%"
	S: * LSUB (\NoSelect) "." #news.comp.mail
	S: A003 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. Under certain circumstances, it can be
	quite slow. In some implementations, the server is obliged to
	open the mailbox read-only internally to obtain certain status
	information. Also unlike the LIST command, the STATUS command
	does not accept wildcards.
	Note: The STATUS command is intended to access
	information mailboxes other than the currently selected
	mailbox. Because the STATUS command can cause the
	mailbox to be opened internally, and because this
	information is available by other means on the selected
	mailbox, the STATUS command SHOULD NOT be used on the
	currently selected mailbox.
	The STATUS command MUST NOT be used as a "check for new
	messages in the selected mailbox" operation (refer to
	sections 7, 7.3.1, and 7.3.2 for more information about
	the proper method for new message checking).
	Because the STATUS command is not guaranteed to be fast
	in its results, clients SHOULD NOT expect to be able to
	issue many consecutive STATUS commands and obtain
	reasonable performance.
	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 unique identifier value of the mailbox. Refer to
	section 2.3.1.1 for more information.
	UIDVALIDITY
	The unique identifier validity value of the mailbox. Refer to
	section 2.3.1.1 for more information.
	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-2822] 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-2822] 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.
	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 message
	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}
	S: + Ready for literal data
	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.
	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
	message 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
	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
	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
	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-2822]/[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). This response SHOULD
	contain the BADCHARSET response code, which MAY list the
	[CHARSET]s supported by the server.
	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.
	<sequence set>
	Messages with message sequence numbers corresponding to the
	specified message sequence number set
	ALL
	All messages in the mailbox; the default initial key for
	ANDing.
	ANSWERED
	Messages with the \Answered flag set.
	BCC <string>
	Messages that contain the specified string in the envelope
	structure's BCC field.
	BEFORE <date>
	Messages whose internal date (disregarding time and timezone)
	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-2822]) and that contains the specified string
	in the text of the header (what comes after the colon). If the
	string to search is zero-length, this matches all messages that
	have a header line with the specified field-name regardless of
	the contents.
	KEYWORD <flag>
	Messages with the specified keyword flag set.
	LARGER <n>
	Messages with an [RFC-2822] 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 (disregarding time and timezone)
	is within the specified date.
	OR <search-key1> <search-key2>
	Messages that match either search key.
	RECENT
	Messages that have the \Recent flag set.
	SEEN
	Messages that have the \Seen flag set.
	SENTBEFORE <date>
	Messages whose [RFC-2822] Date: header (disregarding time and
	timezone) is earlier than the specified date.
	SENTON <date>
	Messages whose [RFC-2822] Date: header (disregarding time and
	timezone) is within the specified date.
	SENTSINCE <date>
	Messages whose [RFC-2822] Date: header (disregarding time and
	timezone) is within or later than the specified date.
	SINCE <date>
	Messages whose internal date (disregarding time and timezone)
	is within or later than the specified date.
	SMALLER <n>
	Messages with an [RFC-2822] size smaller than the specified
	number of octets.
	SUBJECT <string>
	Messages that contain the specified string in the envelope
	structure's SUBJECT field.
	TEXT <string>
	Messages that contain the specified string in the header or
	body of the message.
	TO <string>
	Messages that contain the specified string in the envelope
	structure's TO field.
	UID <sequence set>
	Messages with unique identifiers corresponding to the specified
	unique identifier set. Sequence set ranges are permitted.
	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 flag set.
	UNSEEN
	Messages that do not have the \Seen flag set.
	Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
	S: * SEARCH 2 84 882
	S: A282 OK SEARCH completed
	C: A283 SEARCH TEXT "string not in mailbox"
	S: * SEARCH
	S: A283 OK SEARCH completed
	S: A284 SEARCH CHARSET UTF-8 TEXT {6}
	XXXXXX
	S: * SEARCH 43
	S: A284 OK SEARCH completed
	Note: Since this document is restricted to 7-bit ASCII
	text, it is not possible to show actual UTF-8 data. The
	"XXXXXX" is a placeholder for what would be 6 octets of
	8-bit data in an actual transaction.
	6.4.5. FETCH Command
	Arguments: sequence set
	message data item names or macro
	Responses: untagged responses: FETCH
	Result: OK - fetch completed
	NO - fetch error: can't fetch that data
	BAD - command unknown or arguments invalid
	The FETCH command retrieves data associated with a message in the
	mailbox. The data items to be fetched can be either a single atom
	or a parenthesized list.
	Most data items, identified in the formal syntax under the
	msg-att-static rule, are static and MUST NOT change for any
	particular message. Other data items, identified in the formal
	syntax under the msg-att-dynamic rule, MAY change, either as a
	result of a STORE command or due to external events.
	For example, if a client receives an ENVELOPE for a
	message when it already knows the envelope, it can
	safely ignore the newly transmitted envelope.
	There are three macros which specify commonly-used sets of data
	items, and can be used instead of data items. A macro must be
	used by itself, and not in conjunction with other macros or data
	items.
	ALL
	Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)
	FAST
	Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE)
	FULL
	Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE
	BODY)
	The currently defined data items that can be fetched are:
	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.
	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-2822] 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-2822]) 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. Subsetting does not
	exclude the [RFC-2822] delimiting blank line between the header
	and the body; the blank line is included in all header fetches,
	except in the case of a message which has no body and no blank
	line.
	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-2822] header.
	Here is an example of a complex message with some of its
	part specifiers:
	HEADER ([RFC-2822] header of the message)
	TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
	1 TEXT/PLAIN
	2 APPLICATION/OCTET-STREAM
	3 MESSAGE/RFC822
	3.HEADER ([RFC-2822] header of the message)
	3.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
	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-2822] header of the message)
	4.2.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
	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.
	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-2822] header and [MIME-IMB] headers.
	ENVELOPE
	The envelope structure of the message. This is computed by the
	server by parsing the [RFC-2822] header into the component
	parts, defaulting various fields as necessary.
	FLAGS
	The flags that are set for this message.
	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-2822] 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.
	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: sequence set
	message data item name
	value for message data item
	Responses: untagged responses: FETCH
	Result: OK - store completed
	NO - store error: can't store that data
	BAD - command unknown or arguments invalid
	The STORE command alters data associated with a message in the
	mailbox. Normally, STORE will return the updated value of the
	data with an untagged FETCH response. A suffix of ".SILENT" in
	the data item name prevents the untagged FETCH, and the server
	SHOULD assume that the client has determined the updated value
	itself or does not care about the updated value.
	Note: Regardless of whether or not the ".SILENT" suffix
	was used, the server SHOULD send an untagged FETCH
	response if a change to a message's flags from an
	external source is observed. The intent is that the
	status of the flags is determinate without a race
	condition.
	The currently defined data items that can be stored are:
	FLAGS <flag list>
	Replace the flags for the message (other than \Recent) with the
	argument. The new value of the flags is returned as if a FETCH
	of those flags was done.
	FLAGS.SILENT <flag list>
	Equivalent to FLAGS, but without returning a new value.
	+FLAGS <flag list>
	Add the argument to the flags for the message. The new value
	of the flags is returned as if a FETCH of those flags was done.
	+FLAGS.SILENT <flag list>
	Equivalent to +FLAGS, but without returning a new value.
	-FLAGS <flag list>
	Remove the argument from the flags for the message. The new
	value of the flags is returned as if a FETCH of those flags was
	done.
	-FLAGS.SILENT <flag list>
	Equivalent to -FLAGS, but without returning a new value.
	Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
	S: * 2 FETCH (FLAGS (\Deleted \Seen))
	S: * 3 FETCH (FLAGS (\Deleted))
	S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen))
	S: A003 OK STORE completed
	6.4.7. COPY Command
	Arguments: sequence set
	mailbox name
	Responses: no specific responses for this command
	Result: OK - copy completed
	NO - copy error: can't copy those messages or to that
	name
	BAD - command unknown or arguments invalid
	The COPY command copies the specified message(s) to the end of the
	specified destination mailbox. The flags and internal date of the
	message(s) SHOULD be preserved in the copy.
	If the destination mailbox does not exist, a server SHOULD return
	an error. It SHOULD NOT automatically create the mailbox. Unless
	it is certain that the destination mailbox can not be created, the
	server MUST send the response code "[TRYCREATE]" as the prefix of
	the text of the tagged NO response. This gives a hint to the
	client that it can attempt a CREATE command and retry the COPY if
	the CREATE is successful.
	If the COPY command is unsuccessful for any reason, server
	implementations MUST restore the destination mailbox to its state
	before the COPY attempt.
	Example: C: A003 COPY 2:4 MEETING
	S: A003 OK COPY completed
	6.4.8. UID Command
	Arguments: command name
	command arguments
	Responses: untagged responses: FETCH, SEARCH
	Result: OK - UID command completed
	NO - UID command error
	BAD - command unknown or arguments invalid
	The UID command has two forms. In the first form, it takes as its
	arguments a COPY, FETCH, or STORE command with arguments
	appropriate for the associated command. However, the numbers in
	the sequence set argument are unique identifiers instead of
	message sequence numbers. Sequence set ranges are permitted,
	however, there is no guarantee that unique identifiers be
	contiguous.
	A non-existent unique identifier is ignored without any error
	message generated. Thus it is possible for a UID FETCH command to
	return OK without any data or a UID COPY or UID STORE to return OK
	without performing any operations.
	In the second form, the UID command takes a SEARCH command with
	SEARCH command arguments. The interpretation of the arguments is
	the same as with SEARCH; however, the numbers returned in a SEARCH
	response for a UID SEARCH command are unique identifiers instead
	of message sequence numbers. For example, the command UID SEARCH
	1:100 UID 443:557 returns the unique identifiers corresponding to
	the intersection of two sequence sets; the message sequence number
	range 1:100 and the UID range 443:557.
	Note: in the above example, the UID range 443:557
	appears. The same comment about a non-existent unique
	identifier being ignored without any error message also
	applies here. Hence, even if neither UID 443 or 557
	exist, this range is valid and would include an existing
	UID 495.
	Also note that a UID range of 559:* always includes the
	UID of the last message in the mailbox, even if 559 is
	higher than any assigned UID value. This is because the
	contents of a range are independent of the order of the
	range endpoints. Thus, any UID range with * as one of
	the endpoints indicates at least one message (the
	message with the highest numbered UID), unless the
	mailbox is empty.
	The number after the "*" in an untagged FETCH response is always a
	message sequence number, not a unique identifier, even for a UID
	command response. However, server implementations MUST implicitly
	include the UID message data item as part of any FETCH response
	caused by a UID command, regardless of whether a UID was specified
	as a message data item to the FETCH.
	Example: C: A999 UID FETCH 4827313:4828442 FLAGS
	S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
	S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
	S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
	S: A999 OK UID FETCH completed
	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 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.
	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
	can be tagged or untagged. PREAUTH and BYE are always untagged.
	Status responses MAY include an OPTIONAL "response code". A response
	code consists of data inside square brackets in the form of an atom,
	possibly followed by a space and arguments. The response code
	contains additional information or status codes for client software
	beyond the OK/NO/BAD condition, and are defined when there is a
	specific action that a client can take based upon the additional
	information.
	The currently defined response codes are:
	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.
	BADCHARSET
	Optionally followed by a parenthesized list of charsets. A
	SEARCH failed because the given charset is not supported by
	this implementation. If the optional list of charsets is
	given, this lists the charsets that are supported by this
	implementation.
	CAPABILITY
	Followed by a list of capabilities. This can appear in the
	initial OK or PREAUTH response to transmit an initial
	capabilities list. This makes it unnecessary for a client to
	send a separate CAPABILITY command if it recognizes this
	response.
	PARSE
	The human-readable text represents an error in parsing the
	[RFC-2822] 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 ignore the change or store the
	state change for the remainder of the current session only.
	The PERMANENTFLAGS list can also include the special flag \*,
	which indicates that it is possible to create new keywords by
	attempting to store those flags in the mailbox.
	READ-ONLY
	The mailbox is selected read-only, or its access while selected
	has changed from read-write to read-only.
	READ-WRITE
	The mailbox is selected read-write, or its access while
	selected has changed from read-only to read-write.
	TRYCREATE
	An APPEND or COPY attempt is failing because the target mailbox
	does not exist (as opposed to some other reason). This is a
	hint to the client that the operation can succeed if the
	mailbox is first created by the CREATE command.
	UIDNEXT
	Followed by a decimal number, indicates the next unique
	identifier value. Refer to section 2.3.1.1 for more
	information.
	UIDVALIDITY
	Followed by a decimal number, indicates the unique identifier
	validity value. Refer to section 2.3.1.1 for more information.
	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.
	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
	The BYE response is always untagged, and indicates that the server
	is about to close the connection. The human-readable text MAY be
	displayed to the user in a status report by the client. The BYE
	response is sent under one of four conditions:
	1) as part of a normal logout sequence. The server will close
	the connection after sending the tagged OK response to the
	LOGOUT command.
	2) as a panic shutdown announcement. The server closes the
	connection immediately.
	3) as an announcement of an inactivity autologout. The server
	closes the connection immediately.
	4) as one of three possible greetings at connection startup,
	indicating that the server is not willing to accept a
	connection from this client. The server closes the
	connection immediately.
	The difference between a BYE that occurs as part of a normal
	LOGOUT sequence (the first case) and a BYE that occurs because of
	a failure (the other three cases) is that the connection closes
	immediately in the failure case. In all cases the client SHOULD
	continue to read response data from the server until the
	connection is closed; this will ensure that any pending untagged
	or completion responses are read and processed.
	Example: S: * BYE Autologout; idle for too long
	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".
	In addition, client and server implementations MUST implement the
	STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
	capabilities. See the Security Considerations section for
	important information.
	A capability name which begins with "AUTH=" indicates that the
	server supports that particular authentication mechanism.
	The LOGINDISABLED capability indicates that the LOGIN command is
	disabled, and that the server will respond with a tagged NO
	response to any attempt to use the LOGIN command even if the user
	name and password are valid. An IMAP client MUST NOT issue the
	LOGIN command if the server advertises the LOGINDISABLED
	capability.
	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.
	A server MAY send capabilities automatically, by using the
	CAPABILITY response code in the initial PREAUTH or OK responses,
	and by sending an updated CAPABILITY response code in the tagged
	OK response as part of a successful authentication. It is
	unnecessary for a client to send a separate CAPABILITY command if
	it recognizes these automatic capabilities.
	Example: S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI 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.
	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
	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 transmitted 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 messages).
	The update from the EXISTS response MUST be recorded by the
	client.
	Example: S: * 23 EXISTS
	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
	messages).
	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).
	The EXPUNGE response also decrements the number of messages in the
	mailbox; it is not necessary to send an EXISTS response with the
	new value.
	As a result of the immediate decrement rule, message sequence
	numbers that appear in a set of successive EXPUNGE responses
	depend upon whether the messages are removed starting from lower
	numbers to higher numbers, or from higher numbers to lower
	numbers. For example, if the last 5 messages in a 9-message
	mailbox are expunged; a "lower to higher" server will send five
	untagged EXPUNGE responses for message sequence number 5, whereas
	a "higher to lower server" will send successive untagged EXPUNGE
	responses for message sequence numbers 9, 8, 7, 6, and 5.
	An EXPUNGE response MUST NOT be sent when no command is in
	progress; nor while responding to a FETCH, STORE, or SEARCH
	command. This rule is necessary to prevent a loss of
	synchronization of message sequence numbers between client and
	server. A command is not "in progress" until the complete command
	has been received; in particular, a command is not "in progress"
	during the negotiation of command continuation.
	Note: UID FETCH, UID STORE, and UID SEARCH are different
	commands from FETCH, STORE, and SEARCH. An EXPUNGE
	response MAY be sent during an UID command.
	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.
	Note: The origin octet facility MUST NOT be used by a server
	in a FETCH response unless the client specifically requested
	it by means of a FETCH of a BODY[<section>]<<partial>> data
	item.
	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 7-bit; 8-bit
	characters are not permitted in headers. Note also that the
	[RFC-2822] delimiting blank line between the header and the
	body is not affected by header line subsetting; the blank line
	is always included as part of header data, except in the case
	of a message which has no body and no blank line.
	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 sequence of one or more nested body structures. 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
	BASE64-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 "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 as defined in [DISPOSITION].
	body language
	A string or parenthesized list giving the body language
	value as defined in [LANGUAGE-TAGS].
	body location
	A string list giving the body content URI as defined in
	[LOCATION].
	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].
	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].
	body location
	A string list giving the body content URI as defined in
	[LOCATION].
	Any following extension data are not yet defined in this
	version of the protocol, and would be as described above under
	multipart extension data.
	ENVELOPE
	A parenthesized list that describes the envelope structure of a
	message. This is computed by the server by parsing the
	[RFC-2822] 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-2822] 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.
	If the Date, Subject, In-Reply-To, and Message-ID header lines
	are absent in the [RFC-2822] header, the corresponding member
	of the envelope is NIL; if these header lines are present but
	empty the corresponding member of the envelope is the empty
	string.
	Note: some servers may return a NIL envelope member in the
	"present but empty" case. Clients SHOULD treat NIL and
	empty string as identical.
	Note: [RFC-2822] requires that all messages have a valid
	Date header. Therefore, the date member in the envelope can
	not be NIL or the empty string.
	Note: [RFC-2822] requires that the In-Reply-To and
	Message-ID headers, if present, have non-empty content.
	Therefore, the in-reply-to and message-id members in the
	envelope can not be the empty string.
	If the From, To, cc, and bcc header lines are absent in the
	[RFC-2822] header, or are present but empty, the corresponding
	member of the envelope is NIL.
	If the Sender or Reply-To lines are absent in the [RFC-2822]
	header, or are present but empty, the server sets the
	corresponding member of the envelope to be the same value as
	the from member (the client is not expected to know to do
	this).
	Note: [RFC-2822] requires that all messages have a valid
	From header. Therefore, the from, sender, and reply-to
	members in the envelope can not be NIL.
	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[HEADER]. Note that this did not result in
	\Seen being set, because RFC822.HEADER response data occurs as
	a result of a FETCH of RFC822.HEADER. BODY[HEADER] response
	data occurs as a result of a FETCH of BODY[HEADER] (which sets
	\Seen) or BODY.PEEK[HEADER] (which does not set \Seen).
	RFC822.SIZE
	A number expressing the [RFC-2822] size of the message.
	RFC822.TEXT
	Equivalent to BODY[TEXT].
	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 AUTHENTICATE command to transmit server
	data to the client, and request additional client data. This
	response is also used if an argument to any command is a literal.
	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
	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 (ABNF) notation as specified in [ABNF].
	In the case of alternative or optional rules in which a later rule
	overlaps an earlier rule, the rule which is listed earlier MUST take
	priority. For example, "\Seen" when parsed as a flag is the \Seen
	flag name and not a flag-extension, even though "\Seen" can be parsed
	as a flag-extension. Some, but not all, instances of this rule are
	noted below.
	Note: [ABNF] rules MUST be followed strictly; in
	particular:
	(1) Except as noted otherwise, all alphabetic characters
	are case-insensitive. The use of upper or lower case
	characters to define token strings is for editorial clarity
	only. Implementations MUST accept these strings in a
	case-insensitive fashion.
	(2) In all cases, SP refers to exactly one space. It is
	NOT permitted to substitute TAB, insert additional spaces,
	or otherwise treat SP as being equivalent to LWSP.
	(3) The ASCII NUL character, %x00, MUST NOT be used at any
	time.
	address = "(" addr-name SP addr-adl SP addr-mailbox SP
	addr-host ")"
	addr-adl = nstring
	; Holds route from [RFC-2822] route-addr if
	; non-NIL
	addr-host = nstring
	; NIL indicates [RFC-2822] group syntax.
	; Otherwise, holds [RFC-2822] domain name
	addr-mailbox = nstring
	; NIL indicates end of [RFC-2822] group; if
	; non-NIL and addr-host is NIL, holds
	; [RFC-2822] group name.
	; Otherwise, holds [RFC-2822] local-part
	; after removing [RFC-2822] quoting
	addr-name = nstring
	; If non-NIL, holds phrase from [RFC-2822]
	; mailbox after removing [RFC-2822] quoting
	append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP
	literal
	astring = 1*ASTRING-CHAR / string
	ASTRING-CHAR = ATOM-CHAR / resp-specials
	atom = 1*ATOM-CHAR
	ATOM-CHAR = <any CHAR except atom-specials>
	atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards /
	quoted-specials / resp-specials
	authenticate = "AUTHENTICATE" SP auth-type *(CRLF base64)
	auth-type = atom
	; Defined by [SASL]
	base64 = *(4base64-char) [base64-terminal]
	base64-char = ALPHA / DIGIT / "+" / "/"
	; Case-sensitive
	base64-terminal = (2base64-char "==") / (3base64-char "=")
	body = "(" (body-type-1part / body-type-mpart) ")"
	body-extension = nstring / number /
	"(" body-extension *(SP 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 [SP body-fld-dsp [SP body-fld-lang
	*(SP body-extension)]]
	; MUST NOT be returned on non-extensible
	; "BODY" fetch
	body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang
	*(SP body-extension)]]
	; MUST NOT be returned on non-extensible
	; "BODY" fetch
	body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP
	body-fld-enc SP body-fld-octets
	body-fld-desc = nstring
	body-fld-dsp = "(" string SP body-fld-param ")" / nil
	body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
	"QUOTED-PRINTABLE") DQUOTE) / string
	body-fld-id = nstring
	body-fld-lang = nstring / "(" string *(SP string) ")"
	body-fld-loc = nstring
	body-fld-lines = number
	body-fld-md5 = nstring
	body-fld-octets = number
	body-fld-param = "(" string SP string *(SP string SP string) ")" / nil
	body-type-1part = (body-type-basic / body-type-msg / body-type-text)
	[SP body-ext-1part]
	body-type-basic = media-basic SP body-fields
	; MESSAGE subtype MUST NOT be "RFC822"
	body-type-mpart = 1*body SP media-subtype
	[SP body-ext-mpart]
	body-type-msg = media-message SP body-fields SP envelope
	SP body SP body-fld-lines
	body-type-text = media-text SP body-fields SP 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" *(SP capability) SP "IMAP4rev1"
	*(SP capability)
	; Servers MUST implement the STARTTLS, AUTH=PLAIN,
	; and LOGINDISABLED capabilities
	; Servers which offer RFC 1730 compatibility MUST
	; list "IMAP4" as the first capability.
	CHAR8 = %x01-ff
	; any OCTET except NUL, %x00
	command = tag SP (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
	command-nonauth = login / authenticate / "STARTTLS"
	; Valid only when in Not Authenticated state
	command-select = "CHECK" / "CLOSE" / "EXPUNGE" / copy / fetch / store /
	uid / search
	; Valid only when in Selected state
	continue-req = "+" SP (resp-text / base64) CRLF
	copy = "COPY" SP sequence-set SP mailbox
	create = "CREATE" SP mailbox
	; Use of INBOX gives a NO error
	date = date-text / DQUOTE date-text DQUOTE
	date-day = 1*2DIGIT
	; Day of month
	date-day-fixed = (SP 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 = DQUOTE date-day-fixed "-" date-month "-" date-year
	SP time SP zone DQUOTE
	delete = "DELETE" SP mailbox
	; Use of INBOX gives a NO error
	digit-nz = %x31-39
	; 1-9
	envelope = "(" env-date SP env-subject SP env-from SP env-sender SP
	env-reply-to SP env-to SP env-cc SP env-bcc SP
	env-in-reply-to SP 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" SP mailbox
	fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" /
	fetch-att / "(" fetch-att *(SP 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
	; Does not include "\Recent"
	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-fetch = flag / "\Recent"
	flag-keyword = atom
	flag-list = "(" [flag *(SP flag)] ")"
	flag-perm = flag / "\*"
	greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF
	header-fld-name = astring
	header-list = "(" header-fld-name *(SP header-fld-name) ")"
	list = "LIST" SP mailbox SP list-mailbox
	list-mailbox = 1*list-char / string
	list-char = ATOM-CHAR / list-wildcards / resp-specials
	list-wildcards = "%" / "*"
	literal = "{" number "}" CRLF *CHAR8
	; Number represents the number of CHAR8s
	login = "LOGIN" SP userid SP password
	lsub = "LSUB" SP mailbox SP 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. An astring which consists of
	; the case-insensitive sequence "I" "N" "B" "O" "X"
	; is considered to be INBOX and not an astring.
	; Refer to section 5.1 for further
	; semantic details of mailbox names.
	mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list /
	"LSUB" SP mailbox-list / "SEARCH" *(SP nz-number) /
	"STATUS" SP mailbox SP "("
	[status-att SP number *(SP status-att SP number)] ")" /
	number SP "EXISTS" / number SP "RECENT"
	mailbox-list = "(" [mbx-list-flags] ")" SP
	(DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox
	mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag
	*(SP mbx-list-oflag) /
	mbx-list-oflag *(SP mbx-list-oflag)
	mbx-list-oflag = "\Noinferiors" / flag-extension
	; Other flags; multiple possible per LIST response
	mbx-list-sflag = "\Noselect" / "\Marked" / "\Unmarked"
	; Selectability flags; only one per LIST response
	media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" / "MESSAGE" /
	"VIDEO") DQUOTE) / string) SP media-subtype
	; Defined in [MIME-IMT]
	media-message = DQUOTE "MESSAGE" DQUOTE SP DQUOTE "RFC822" DQUOTE
	; Defined in [MIME-IMT]
	media-subtype = string
	; Defined in [MIME-IMT]
	media-text = DQUOTE "TEXT" DQUOTE SP media-subtype
	; Defined in [MIME-IMT]
	message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att))
	msg-att = "(" (msg-att-dynamic / msg-att-static)
	*(SP (msg-att-dynamic / msg-att-static)) ")"
	msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")"
	; MAY change for a message
	msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time /
	"RFC822" [".HEADER" / ".TEXT"] SP nstring /
	"RFC822.SIZE" SP number / "BODY" ["STRUCTURE"] SP body /
	"BODY" section ["<" number ">"] SP nstring /
	"UID" SP uniqueid
	; MUST NOT change for a message
	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 = DQUOTE *QUOTED-CHAR DQUOTE
	QUOTED-CHAR = <any TEXT-CHAR except quoted-specials> /
	"\" quoted-specials
	quoted-specials = DQUOTE / "\"
	rename = "RENAME" SP mailbox SP mailbox
	; Use of INBOX as a destination gives a NO error
	response = *(continue-req / response-data) response-done
	response-data = "*" SP (resp-cond-state / resp-cond-bye /
	mailbox-data / message-data / capability-data) CRLF
	response-done = response-tagged / response-fatal
	response-fatal = "*" SP resp-cond-bye CRLF
	; Server closes connection immediately
	response-tagged = tag SP resp-cond-state CRLF
	resp-cond-auth = ("OK" / "PREAUTH") SP resp-text
	; Authentication condition
	resp-cond-bye = "BYE" SP resp-text
	resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text
	; Status condition
	resp-specials = "]"
	resp-text = ["[" resp-text-code "]" SP] text
	resp-text-code = "ALERT" /
	"BADCHARSET" [SP "(" astring *(SP astring) ")" ] /
	capability-data / "PARSE" /
	"PERMANENTFLAGS" SP "(" [flag-perm *(SP flag-perm)] ")" /
	"READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
	"UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number /
	"UNSEEN" SP nz-number /
	atom [SP 1*<any TEXT-CHAR except "]">]
	search = "SEARCH" [SP "CHARSET" SP astring] 1*(SP search-key)
	; CHARSET argument to MUST be registered with IANA
	search-key = "ALL" / "ANSWERED" / "BCC" SP astring /
	"BEFORE" SP date / "BODY" SP astring /
	"CC" SP astring / "DELETED" / "FLAGGED" /
	"FROM" SP astring / "KEYWORD" SP flag-keyword / "NEW" /
	"OLD" / "ON" SP date / "RECENT" / "SEEN" /
	"SINCE" SP date / "SUBJECT" SP astring /
	"TEXT" SP astring / "TO" SP astring /
	"UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
	"UNKEYWORD" SP flag-keyword / "UNSEEN" /
	; Above this line were in [IMAP2]
	"DRAFT" / "HEADER" SP header-fld-name SP astring /
	"LARGER" SP number / "NOT" SP search-key /
	"OR" SP search-key SP search-key /
	"SENTBEFORE" SP date / "SENTON" SP date /
	"SENTSINCE" SP date / "SMALLER" SP number /
	"UID" SP sequence-set / "UNDRAFT" / sequence-set /
	"(" search-key *(SP search-key) ")"
	section = "[" [section-spec] "]"
	section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list /
	"TEXT"
	; top-level or MESSAGE/RFC822 part
	section-part = nz-number *("." nz-number)
	; body part nesting
	section-spec = section-msgtext / (section-part ["." section-text])
	section-text = section-msgtext / "MIME"
	; text other than actual body part (headers, etc.)
	select = "SELECT" SP mailbox
	seq-number = nz-number / "*"
	; message sequence number (COPY, FETCH, STORE
	; commands) or unique identifier (UID COPY,
	; UID FETCH, UID STORE commands).
	; * represents the largest number in use. In
	; the case of message sequence numbers, it is
	; the number of messages in a non-empty mailbox.
	; In the case of unique identifiers, it is the
	; unique identifier of the last message in the
	; mailbox or, if the mailbox is empty, the
	; UIDNEXT value.
	; The server should respond with a tagged BAD
	; response to a command that uses a message
	; sequence number greater than the number of
	; messages in the selected mailbox. This
	; includes "*" if the selected mailbox is empty.
	seq-range = seq-number ":" seq-number
	; two seq-number values and all values between
	; these two regardless of order.
	; Example: 2:4 and 4:2 are equivalent and indicate
	; values 2, 3, and 4.
	; Example: a unique identifer sequence range of
	; 3291:* includes the UID of the last message in
	; the mailbox, even if that value is less than 3291.
	sequence-set = (seq-number / seq-range) / *("," sequence-set)
	; set of seq-number values, regardless of order.
	; Servers MAY coalesce overlaps and/or execute the
	; sequence in any order.
	; Example: a message sequence number set of 2,4:7,9,12:*
	; for a mailbox with 15 messages is equivalent to
	; 2,4,5,6,7,9,12,13,14,15
	; Example: a message sequence number set of *:4,5:7
	; for a mailbox with 10 messages is equivalent to
	; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and
	; overlap coalesced to be 4,5,6,7,8,9,10.
	status = "STATUS" SP mailbox SP "(" status-att *(SP status-att) ")"
	status-att = "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
	"UNSEEN"
	store = "STORE" SP sequence-set SP store-att-flags
	store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP
	(flag-list / (flag *(SP flag)))
	string = quoted / literal
	subscribe = "SUBSCRIBE" SP mailbox
	tag = 1*<any ASTRING-CHAR except "+">
	text = 1*TEXT-CHAR
	TEXT-CHAR = <any CHAR except CR and LF>
	time = 2DIGIT ":" 2DIGIT ":" 2DIGIT
	; Hours minutes seconds
	uid = "UID" SP (copy / fetch / search / store)
	; Unique identifiers used instead of message
	; sequence numbers
	uniqueid = nz-number
	; Strictly ascending
	unsubscribe = "UNSUBSCRIBE" SP mailbox
	userid = astring
	x-command = "X" atom <experimental command arguments>
	zone = ("+" / "-") 4DIGIT
	; Signed four-digit value of hhmm representing
	; hours and minutes east 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 2060,
	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 protection from snooping is
	negotiated, either by the use of STARTTLS, privacy protection is
	negotiated in the AUTHENTICATE command, or some other protection
	mechanism is in effect.
	11.1. STARTTLS Security Considerations
	The specification of the STARTTLS command and LOGINDISABLED
	capability in this document replaces that in [IMAP-TLS]. [IMAP-TLS]
	remains normative for the PLAIN [SASL] authenticator.
	IMAP client and server implementations MUST implement the
	TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suit, and SHOULD implement the
	TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite. This is
	important as it assures that any two compliant implementations can be
	configured to interoperate. All other cipher suites are OPTIONAL.
	Note that this is a change from section 2.1 of [IMAP-TLS].
	During the [TLS] negotiation, the client MUST check its understanding
	of the server hostname against the server's identity as presented in
	the server Certificate message, in order to prevent man-in-the-middle
	attacks. If the match fails, the client SHOULD either ask for
	explicit user confirmation, or terminate the connection and indicate
	the server's identity is suspect. Matching is performed according to
	these rules:
	The client MUST use the server hostname it used to open the
	connection as the value to compare against the server name
	as expressed in the server certificate. The client MUST
	NOT use any form of the server hostname derived from an
	insecure remote source (e.g., insecure DNS lookup). CNAME
	canonicalization is not done.
	If a subjectAltName extension of type dNSName is present in
	the certificate, it SHOULD be used as the source of the
	server's identity.
	Matching is case-insensitive.
	A "*" wildcard character MAY be used as the left-most name
	component in the certificate. For example, *.example.com
	would match a.example.com, foo.example.com, etc. but would
	not match example.com.
	If the certificate contains multiple names (e.g. more than
	one dNSName field), then a match with any one of the fields
	is considered acceptable.
	Both the client and server MUST check the result of the STARTTLS
	command and subsequent [TLS] negotiation to see whether acceptable
	authentication or privacy was achieved.
	11.2. Other Security Considerations
	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 with a [SASL] mechanism
	that does not use plaintext passwords, by first negotiating
	encryption via STARTTLS or some other protection mechanism.
	A server implementation MUST implement a configuration in which, at
	the time of authentication, requires that:
	(1) The STARTTLS command command has been negotiated.
	OR
	(2) Some other mechanism that protects the session from password
	snooping has been provided.
	OR
	(3) The following measures are in place:
	(a) The LOGINDISABLED capability is advertised, and [SASL]
	mechanisms (such as PLAIN) which use plaintext passwords are
	NOT advertised in the CAPABILITY list.
	AND
	(b) The LOGIN command returns an error even if the password is
	correct.
	AND
	(c) The AUTHENTICATE command returns an error with all [SASL]
	mechanisms which use plaintext passwords, even if the password
	is correct.
	A server error message for a failing LOGIN command SHOULD NOT specify
	that the user name, as opposed to the password, is invalid.
	A server SHOULD have mechanisms in place to limit or delay failed
	AUTHENTICATE/LOGIN attempts.
	Additional security considerations are discussed in the section
	discussing the AUTHENTICATE and LOGIN commands.
	12. IANA Considerations
	IMAP4 capabilities are registered by publishing a standards track or
	IESG approved experimental RFC. The registry is currently located
	at:
	http://www.iana.org/assignments/imap4-capabilities
	As this specification revises the STARTTLS and LOGINDISABLED
	extensions previously defined in [IMAP-TLS], the registry will be
	updated accordingly.
	13. Author's Address
	Mark R. Crispin
	Networks and Distributed Computing
	University of Washington
	4545 15th Avenue NE
	Seattle, WA 98105-4527
	Phone: (206) 543-5762
	EMail: MRC@CAC.Washington.EDU
	Appendices
	A. References
	The following documents contain definitions or specifications which
	are necessary to understand this document properly:
	[ABNF] Crocker, D., and Overell, P. "Augmented BNF for Syntax
	Specifications: ABNF", RFC 2234, November 1997.
	[ANONYMOUS] Newman, C. "Anonymous SASL Mechanism", RFC 2245, November
	1997.
	[CHARSET] Freed, N., and Postel, J. "IANA Character Set Registration
	Procedures", RFC 2978, October 2000.
	[DIGEST-MD5] Leach, P., and Newman, C. "Using Digest Authentication
	as a SASL Mechanism", RFC 2831, May 2000.
	[DISPOSITION] Troost, R., Dorner, S., and Moore, K. "Communicating
	Presentation Information in Internet Messages: The
	Content-Disposition Header", RFC 2183, August 1997.
	[IMAP-TLS] Newman, C. "Using TLS with IMAP, POP3 and ACAP", RFC 2595,
	June 1999.
	[KEYWORDS] Bradner, S. "Key words for use in RFCs to Indicate
	Requirement Levels", RFC 2119, Harvard University, March 1997.
	[LANGUAGE-TAGS] Alvestrand, H. "Tags for the Identification of
	Languages", RFC 1766, March 1995.
	[LOCATION] Palme, J., Hopmann, A., and Shelness, N. "MIME
	Encapsulation of Aggregate Documents, such as HTML (MHTML)", RFC
	2557, March 1999.
	[MD5] Myers, J., and Rose, M. "The Content-MD5 Header Field", RFC
	1864, October 1995.
	[MIME-HDRS] Moore, K. "MIME (Multipurpose Internet Mail Extensions)
	Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047,
	November 1996.
	[MIME-IMB] Freed, N., and Borenstein, N. "MIME (Multipurpose Internet
	Mail Extensions) Part One: Format of Internet Message Bodies", RFC
	2045, November 1996.
	[MIME-IMT] Freed, N., and Borenstein, N. "MIME (Multipurpose Internet
	Mail Extensions) Part Two: Media Types", RFC 2046, November 1996.
	[RFC-2822] Resnick, P. "Internet Message Format", RFC 2822, April
	2001.
	[SASL] Myers, J. "Simple Authentication and Security Layer (SASL)",
	RFC 2222, October 1997.
	[TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
	2246, January 1999.
	[UTF-7] Goldsmith, D., and Davis, M. "UTF-7: A Mail-Safe
	Transformation Format of Unicode", RFC 2152, May 1997.
	The following documents describe quality-of-implementation issues
	which should be carefully considered when implementing this protocol:
	[IMAP-IMPLEMENTATION] Leiba, B. "IMAP Implementation
	Recommendations", RFC 2683, September 1999.
	[IMAP-MULTIACCESS] Gahrns, M. "IMAP4 Multi-Accessed Mailbox
	Practice", RFC 2180, July 1997.
	The following documents describe additional information related to
	the architecture of this protocol:
	[IMAP-DISC] Austein, R. "Synchronization Operations for Disconnected
	IMAP4 Clients", Work in Progress.
	[IMAP-MODEL] Crispin, M. "Distributed Electronic Mail Models in
	IMAP4", RFC 1733, December 1994.
	The following documents describe related protocols:
	[ACAP] Newman, C., and Myers, J. "ACAP -- Application Configuration
	Access Protocol", RFC 2244, November 1997.
	[SMTP] Klensin, J. "Simple Mail Transfer Protocol", STD 10, RFC 2821,
	April 2001.
	The following documents are historical or describe historical aspects
	of this protocol:
	[IMAP-COMPAT] Crispin, M. "IMAP4 Compatibility with IMAP2bis", RFC
	2061, December 1996.
	[IMAP-HISTORICAL] Crispin, M. "IMAP4 Compatibility with IMAP2 and
	IMAP2bis", RFC 1732, December 1994.
	[IMAP-OBSOLETE] Crispin, M. "Internet Message Access Protocol -
	Obsolete Syntax", RFC 2062, December 1996.
	[IMAP2] Crispin, M. "Interactive Mail Access Protocol - Version 2",
	RFC 1176, August 1990.
	[RFC-822] Crocker, D. "Standard for the Format of ARPA Internet Text
	Messages", STD 11, RFC 822, August 1982.
	[RFC-821] Postel, J. "Simple Mail Transfer Protocol", STD 10, RFC
	821, August 1982.
	B. Changes from RFC 2060
	1) Clarify description of unique identifiers and their semantics.
	2) Fix SELECT description to clarify that UIDVALIDITY is required in
	the SELECT and EXAMINE responses.
	3) Added an example of a failing search
	4) Correct store-att-flags: "#flag" should be "1#flag".
	5) Made search and section rules clearer.
	6) Correct the STORE example.
	7) Correct "BASE645" misspelling.
	8) Remove extraneous close parenthesis in example of two-part message
	with text and BASE64 attachment.
	9) Remove obsolete "MAILBOX" response from mailbox-data.
	10) A spurious "<" in the rule for mailbox-data was removed.
	11) Add CRLF to continue-req.
	12) Specifically exclude "]" from the atom in resp-text-code.
	13) Clarify that clients and servers should adhere to the protocol
	syntax strictly.
	14) Emphasize in 5.2 that EXISTS can not be used to shrink a mailbox.
	15) Add NEWNAME to resp-text-code.
	16) Clarify that the empty string, not NIL, is used as arguments to
	LIST.
	17) Clarify that NIL can be returned as a hierarchy delimiter for the
	empty string mailbox name argument if the mailbox namespace is flat.
	18) Clarify that addr-mailbox and addr-name have RFC-2822 quoting
	removed.
	19) Update UTF-7 reference.
	20) Fix example in 6.3.11.
	21) Clarify that non-existent UIDs are ignored.
	22) Update DISPOSITION reference.
	23) Expand state diagram.
	24) Clarify that partial fetch responses are only returned in
	response to a partial fetch command.
	25) Add UIDNEXT response code. Correct UIDVALIDITY definition
	reference.
	26) Further clarification of "can" vs. "MAY".
	27) Reference RFC-2119.
	28) Clarify that superfluous shifts are not permitted in modified
	UTF-7.
	29) Clarify that there are no implicit shifts in modified UTF-7.
	30) Clarify that "INBOX" in a mailbox name is always INBOX, even if
	it is given as an string.
	31) Add missing open parenthesis in media-basic grammar rule.
	32) Correct attribute syntax in mailbox-data.
	33) Add UIDNEXT to EXAMINE responses
	34) Clarify UNSEEN, PERMANENTFLAGS, UIDVALIDITY, and UIDNEXT
	responses in SELECT and EXAMINE. They are required now, but weren't
	in older versions.
	35) Update references with RFC numbers.
	36) Flush text-mime2.
	37) Clarify that modified UTF-7 names must be case-sensitive and that
	violating the convention should be avoided.
	38) Correct UID FETCH example.
	39) Clarify UID FETCH, UID STORE, and UID SEARCH vs. untagged EXPUNGE
	responses.
	40) Clarify the use of the word "convention".
	41) Clarify that a command is not "in progress" until it has been
	fully received (specifically, that a command is not "in progress"
	during command continuation negotiation).
	42) Clarify envelope defaulting.
	43) Clarify that SP means one and only one space character.
	44) Forbid silly states in LIST response.
	45) Clarify that the ENVELOPE, INTERNALDATE, RFC822*, BODY*, and UID
	for a message is static.
	46) Add BADCHARSET response code.
	47) Update formal syntax to [ABNF] conventions.
	48) Clarify trailing hierarchy delimiter in CREATE semantics.
	49) Clarify that the "blank line" is the [RFC-2822] delimiting blank
	line.
	50) Clarify that RENAME should also create hierarchy as needed for
	the command to complete.
	51) Fix body-ext-mpart to not require language if disposition
	present.
	52) Clarify the RFC822.HEADER response.
	53) Correct missing space after charset astring in search.
	54) Correct missing quote for BADCHARSET in resp-text-code.
	55) Clarify that ALL, FAST, and FULL preclude any other data items
	appearing.
	56) Clarify semantics of reference argument in LIST.
	57) Clarify that a null string for SEARCH HEADER X-FOO means any
	message with a header line with a field-name of X-FOO regardless of
	the text of the header.
	58) Specifically reserve 8-bit mailbox names for future use as UTF-8.
	59) It is not an error for the client to store a flag that isn't in
	the PERMANENTFLAGS list; however, the server will either ignore the
	change or make the change in the session only.
	60) Correct/clarify the text regarding superfluous shifts.
	61) Correct typographic errors in the "Changes" section.
	62) Clarify that STATUS must not be used to check for new messages in
	the selected mailbox
	63) Clarify LSUB behavior with "%" wildcard.
	64) Change AUTHORIZATION to AUTHENTICATE in section 7.5.
	65) Clarify description of multipart body type.
	66) Clarify that STORE FLAGS does not affect \Recent.
	67) Change "west" to "east" in description of timezone.
	68) Clarify that commands which break command pipelining must wait
	for a completion result response.
	69) Clarify that EXAMINE does not affect \Recent.
	70) Make description of MIME structure consistent.
	71) Clarify that date searches disregard the time and timezone of the
	INTERNALDATE or Date: header. In other words, "ON 13-APR-2000" means
	messages with an INTERNALDATE text which starts with "13-APR-2000",
	even if timezone differential from the local timezone is sufficient
	to move that INTERNALDATE into the previous or next day.
	72) Clarify that the header fetches don't add a blank line if one
	isn't in the [RFC-2822] message.
	73) Clarify (in discussion of UIDs) that messages are immutable.
	74) Add an example of CHARSET searching.
	75) Clarify in SEARCH that keywords are a type of flag.
	76) Clarify the mandatory nature of the SELECT data responses.
	77) Add optional CAPABILITY response code in the initial OK or
	PREAUTH.
	78) Add note that server can send an untagged CAPABILITY command as
	part of the responses to AUTHENTICATE and LOGIN.
	79) Remove statement about it being unnecessary to issue a CAPABILITY
	command more than once in a connection. That statement is no longer
	true.
	80) Clarify that untagged EXPUNGE decrements the number of messages
	in the mailbox.
	81) Fix definition of "body" (concatenation has tighter binding than
	alternation).
	82) Add a new "Special Notes to Implementors" section with reference
	to [IMAP-IMPLEMENTATION].
	83) Clarify that an untagged CAPABILITY response to an AUTHENTICATE
	command should only be done if a security layer was not negotiated.
	84) Change the definition of atom to exclude "]". Update astring to
	include "]" for compatiblity with the past. Remove resp-text-atom.
	85) Remove NEWNAME. It can't work because mailbox names can be
	literals and can include "]". Functionality can be addressed via
	referrals.
	86) Move modified UTF-7 rationale in order to have more logical
	paragraph flow.
	87) Clarify UID uniqueness guarantees with the use of MUST.
	88) Note that clients should read response data until the connection
	is closed instead of immediately closing on a BYE.
	89) Change RFC-822 references to RFC-2822.
	90) Clarify that RFC-2822 should be followed instead of RFC-822.
	91) Change recommendation of optional automatic capabilities in LOGIN
	and AUTHENTICATE to use the CAPABILITY response code in the tagged
	OK. This is more interoperable than an unsolicited untagged
	CAPABILITY response.
	92) STARTTLS and AUTH=PLAIN are mandatory to implement; add
	recommendations for other [SASL] mechanisms.
	93) Clarify that a "connection" (as opposed to "server" or "command")
	is in one of the four states.
	94) Clarify that a failed or rejected command does not change state.
	95) Split references between normative and informative.
	96) Discuss authentication failure issues in security section.
	97) Clarify that a data item is not necessarily of only one data
	type.
	98) Clarify that sequence ranges are independent of order.		Title: INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
			Author(s): M. Crispin
			Status: Standards Track
			Date: March 2003
			Mailbox: MRC@CAC.Washington.EDU
			Pages: 108
			Characters: 227640
			Obsoletes: 2060
	99) Change an example to clarify that superfluous shifts in		I-D Tag: draft-crispin-imapv-20.txt
	Modified-UTF7 can not be fixed just by omitting the shift. The
	entire string must be recalculated.
	100) Change Envelope Structure definition since [RFC-2822] uses		URL: ftp://ftp.rfc-editor.org/in-notes/rfc3501.txt
	"envelope" to refer to the [SMTP] envelope and not the envelope data
	that appears in the [RFC-2822] header.
	101) Expand on RFC822.HEADER response data vs. BODY[HEADER].		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 mailboxes (remote message
			folders) in a way that is functionally equivalent to local folders.
			IMAP4rev1 also provides the capability for an offline client to
			resynchronize with the server.
	102) Clarify Logout state semantics, change ASCII art.		IMAP4rev1 includes operations for creating, deleting, and renaming
			mailboxes, checking for new messages, permanently removing messages,
			setting and clearing flags, RFC 2822 and RFC 2045 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.
	103) Security changes to comply with IESG requirements.		IMAP4rev1 supports a single server. A mechanism for accessing
			configuration information to support multiple IMAP4rev1 servers is
			discussed in RFC 2244.
	104) Add definition for body URI.		IMAP4rev1 does not specify a means of posting mail; this function is
			handled by a mail transfer protocol such as RFC 2821.
	105) Break sequence range definition into three rules, with rewritten		This is now a Proposed Standard Protocol.
	descriptions for each.
	106) Move STARTTLS and LOGINDISABLED here from [IMAP-TLS].		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.
	107) Add IANA Considerations section.		This announcement is sent to the IETF list and the RFC-DIST list.
			Requests to be added to or deleted from the IETF distribution list
			should be sent to IETF-REQUEST@IETF.ORG. Requests to be
			added to or deleted from the RFC-DIST distribution list should
			be sent to RFC-DIST-REQUEST@RFC-EDITOR.ORG.
	C. Key Word Index		Details on obtaining RFCs via FTP or EMAIL may be obtained by sending
			an EMAIL message to rfc-info@RFC-EDITOR.ORG with the message body
			help: ways_to_get_rfcs. For example:
	+FLAGS <flag list> (store command data item) ............... 53		To: rfc-info@RFC-EDITOR.ORG
	+FLAGS.SILENT <flag list> (store command data item) ........ 53		Subject: getting rfcs
	-FLAGS <flag list> (store command data item) ............... 53
	-FLAGS.SILENT <flag list> (store command data item) ........ 54
	ALERT (response code) ...................................... 58
	ALL (fetch item) ........................................... 49
	ALL (search key) ........................................... 45
	ANSWERED (search key) ...................................... 45
	APPEND (command) ........................................... 41
	AUTHENTICATE (command) ..................................... 24
	BAD (response) ............................................. 61
	BADCHARSET (response code) ................................. 58
	BCC <string> (search key) .................................. 45
	BEFORE <date> (search key) ................................. 45
	BODY (fetch item) .......................................... 49
	BODY (fetch result) ........................................ 68
	BODY <string> (search key) ................................. 46
	BODY.PEEK[<section>]<<partial>> (fetch item) ............... 51
	BODYSTRUCTURE (fetch item) ................................. 52
	BODYSTRUCTURE (fetch result) ............................... 68
	BODY[<section>]<<origin octet>> (fetch result) ............. 68
	BODY[<section>]<<partial>> (fetch item) .................... 49
	BYE (response) ............................................. 61
	Body Structure (message attribute) ......................... 9
	CAPABILITY (command) ....................................... 20
	CAPABILITY (response code) ................................. 58
	CAPABILITY (response) ...................................... 62
	CC <string> (search key) ................................... 46
	CHECK (command) ............................................ 42
	CLOSE (command) ............................................ 43
	COPY (command) ............................................. 54
	CREATE (command) ........................................... 30
	DELETE (command) ........................................... 31
	DELETED (search key) ....................................... 46
	DRAFT (search key) ......................................... 46
	ENVELOPE (fetch item) ...................................... 52
	ENVELOPE (fetch result) .................................... 71
	EXAMINE (command) .......................................... 30
	EXISTS (response) .......................................... 66
	EXPUNGE (command) .......................................... 43
	EXPUNGE (response) ......................................... 67
	Envelope Structure (message attribute) ..................... 9
	FAST (fetch item) .......................................... 49
	FETCH (command) ............................................ 48
	FETCH (response) ........................................... 68
	FLAGGED (search key) ....................................... 46
	FLAGS (fetch item) ......................................... 52
	FLAGS (fetch result) ....................................... 73
	FLAGS (response) ........................................... 65
	FLAGS <flag list> (store command data item) ................ 53
	FLAGS.SILENT <flag list> (store command data item) ......... 53
	FROM <string> (search key) ................................. 46
	FULL (fetch item) .......................................... 49
	Flags (message attribute) .................................. 7
	HEADER (part specifier) .................................... 50
	HEADER <field-name> <string> (search key) .................. 46
	HEADER.FIELDS <header-list> (part specifier) ............... 50
	HEADER.FIELDS.NOT <header-list> (part specifier) ........... 50
	INTERNALDATE (fetch item) .................................. 52
	INTERNALDATE (fetch result) ................................ 73
	Internal Date (message attribute) .......................... 9
	KEYWORD <flag> (search key) ................................ 46
	Keyword (type of flag) ..................................... 8
	LARGER <n> (search key) .................................... 46
	LIST (command) ............................................. 35
	LIST (response) ............................................ 63
	LOGIN (command) ............................................ 26
	LOGOUT (command) ........................................... 22
	LSUB (command) ............................................. 38
	LSUB (response) ............................................ 64
	MAY (specification requirement term) ....................... 1
	MESSAGES (status item) ..................................... 40
	MIME (part specifier) ...................................... 50
	MUST (specification requirement term) ...................... 1
	MUST NOT (specification requirement term) .................. 1
	Message Sequence Number (message attribute) ................ 7
	NEW (search key) ........................................... 46
	NO (response) .............................................. 60
	NOOP (command) ............................................. 21
	NOT <search-key> (search key) .............................. 46
	OK (response) .............................................. 60
	OLD (search key) ........................................... 46
	ON <date> (search key) ..................................... 47
	OPTIONAL (specification requirement term) .................. 1
	OR <search-key1> <search-key2> (search key) ................ 47
	PARSE (response code) ...................................... 58
	PERMANENTFLAGS (response code) ............................. 59
	PREAUTH (response) ......................................... 61
	Permanent Flag (class of flag) ............................. 8
	READ-ONLY (response code) .................................. 59
	READ-WRITE (response code) ................................. 59
	RECENT (response) .......................................... 66
	RECENT (search key) ........................................ 47
	RECENT (status item) ....................................... 40
	RENAME (command) ........................................... 33
	REQUIRED (specification requirement term) .................. 1
	RFC822 (fetch item) ........................................ 52
	RFC822 (fetch result) ...................................... 73
	RFC822.HEADER (fetch item) ................................. 52
	RFC822.HEADER (fetch result) ............................... 73
	RFC822.SIZE (fetch item) ................................... 52
	RFC822.SIZE (fetch result) ................................. 73
	RFC822.TEXT (fetch item) ................................... 52
	RFC822.TEXT (fetch result) ................................. 73
	SEARCH (command) ........................................... 44
	SEARCH (response) .......................................... 65
	SEEN (search key) .......................................... 47
	SELECT (command) ........................................... 28
	SENTBEFORE <date> (search key) ............................. 47
	SENTON <date> (search key) ................................. 47
	SENTSINCE <date> (search key) .............................. 47
	SHOULD (specification requirement term) .................... 1
	SHOULD NOT (specification requirement term) ................ 1
	SINCE <date> (search key) .................................. 47
	SMALLER <n> (search key) ................................... 47
	STARTTLS (command) ......................................... 23
	STATUS (command) ........................................... 39
	STATUS (response) .......................................... 65
	STORE (command) ............................................ 52
	SUBJECT <string> (search key) .............................. 47
	SUBSCRIBE (command) ........................................ 34
	Session Flag (class of flag) ............................... 8
	System Flag (type of flag) ................................. 7
	TEXT (part specifier) ...................................... 50
	TEXT <string> (search key) ................................. 47
	TO <string> (search key) ................................... 47
	TRYCREATE (response code) .................................. 59
	UID (command) .............................................. 54
	UID (fetch item) ........................................... 52
	UID (fetch result) ......................................... 73
	UID <sequence set> (search key) ............................ 48
	UIDNEXT (response code) .................................... 59
	UIDNEXT (status item) ...................................... 40
	UIDVALIDITY (response code) ................................ 59
	UIDVALIDITY (status item) .................................. 40
	UNANSWERED (search key) .................................... 48
	UNDELETED (search key) ..................................... 48
	UNDRAFT (search key) ....................................... 48
	UNFLAGGED (search key) ..................................... 48
	UNKEYWORD <flag> (search key) .............................. 48
	UNSEEN (response code) ..................................... 59
	UNSEEN (search key) ........................................ 48
	UNSEEN (status item) ....................................... 40
	UNSUBSCRIBE (command) ...................................... 35
	Unique Identifier (UID) (message attribute) ................ 5
	X<atom> (command) .......................................... 56
	[RFC-2822] Size (message attribute) ........................ 9
	\Answered (system flag) .................................... 8
	\Deleted (system flag) ..................................... 8
	\Draft (system flag) ....................................... 8
	\Flagged (system flag) ..................................... 8
	\Marked (mailbox name attribute) ........................... 64
	\Noinferiors (mailbox name attribute) ...................... 63
	\Noselect (mailbox name attribute) ......................... 63
	\Recent (system flag) ...................................... 8
	\Seen (system flag) ........................................ 8
	\Unmarked (mailbox name attribute) ......................... 64
	Table of Contents		help: ways_to_get_rfcs
	IMAP4rev1 Protocol Specification .................................. 1		Requests for special distribution should be addressed to either the
	1. How to Read This Document ................................. 1		author of the RFC in question, or to RFC-Manager@RFC-EDITOR.ORG. Unless
	1.1. Organization of This Document ............................. 1		specifically noted otherwise on the RFC itself, all RFCs are for
	1.2. Conventions Used in This Document ......................... 1		unlimited distribution.echo
	1.3. Special Notes to Implementors ............................. 2		Submissions for Requests for Comments should be sent to
	2. Protocol Overview ......................................... 3		RFC-EDITOR@RFC-EDITOR.ORG. Please consult RFC 2223, Instructions to RFC
	2.1. Link Level ................................................ 3		Authors, for further information.
	2.2. Commands and Responses .................................... 3
	2.2.1. Client Protocol Sender and Server Protocol Receiver ....... 3
	2.2.2. Server Protocol Sender and Client Protocol Receiver ....... 4
	2.3. Message Attributes ........................................ 5
	2.3.1. Message Numbers ........................................... 5
	2.3.1.1. Unique Identifier (UID) Message Attribute ......... 5
	2.3.1.2. Message Sequence Number Message Attribute ......... 7
	2.3.2. Flags Message Attribute ................................... 7
	2.3.3. Internal Date Message Attribute ........................... 9
	2.3.4. [RFC-2822] Size Message Attribute ......................... 9
	2.3.5. Envelope Structure Message Attribute ...................... 9
	2.3.6. Body Structure Message Attribute .......................... 9
	2.4. Message Texts ............................................. 9
	3. State and Flow Diagram .................................... 10
	3.1. Not Authenticated State ................................... 10
	3.2. Authenticated State ....................................... 10
	3.3. Selected State ............................................ 10
	3.4. Logout State .............................................. 10
	4. Data Formats .............................................. 12
	4.1. Atom ...................................................... 12
	4.2. Number .................................................... 12
	4.3. String .................................................... 12
	4.3.1. 8-bit and Binary Strings .................................. 13
	4.4. Parenthesized List ........................................ 13
	4.5. NIL ....................................................... 13
	5. Operational Considerations ................................ 14
	5.1. Mailbox Naming ............................................ 14
	5.1.1. Mailbox Hierarchy Naming .................................. 15
	5.1.2. Mailbox Namespace Naming Convention ....................... 15
	5.1.3. Mailbox International Naming Convention ................... 15
	5.2. Mailbox Size and Message Status Updates ................... 17
	5.3. Response when no Command in Progress ...................... 17
	5.4. Autologout Timer .......................................... 18
	5.5. Multiple Commands in Progress ............................. 18
	6. Client Commands ........................................... 20
	6.1. Client Commands - Any State ............................... 20
	6.1.1. CAPABILITY Command ........................................ 20
	6.1.2. NOOP Command .............................................. 21
	6.1.3. LOGOUT Command ............................................ 22
	6.2. Client Commands - Not Authenticated State ................. 22
	6.2.1. STARTTLS Command .......................................... 23
	6.2.2. AUTHENTICATE Command ...................................... 24
	6.2.3. LOGIN Command ............................................. 26
	6.3. Client Commands - Authenticated State ..................... 28
	6.3.1. SELECT Command ............................................ 28
	6.3.2. EXAMINE Command ........................................... 30
	6.3.3. CREATE Command ............................................ 30
	6.3.4. DELETE Command ............................................ 31
	6.3.5. RENAME Command ............................................ 33
	6.3.6. SUBSCRIBE Command ......................................... 34
	6.3.7. UNSUBSCRIBE Command ....................................... 35
	6.3.8. LIST Command .............................................. 35
	6.3.9. LSUB Command .............................................. 38
	6.3.10. STATUS Command ............................................ 39
	6.3.11. APPEND Command ............................................ 41
	6.4. Client Commands - Selected State .......................... 42
	6.4.1. CHECK Command ............................................. 42
	6.4.2. CLOSE Command ............................................. 43
	6.4.3. EXPUNGE Command ........................................... 43
	6.4.4. SEARCH Command ............................................ 44
	6.4.5. FETCH Command ............................................. 48
	6.4.6. STORE Command ............................................. 52
	6.4.7. COPY Command .............................................. 54
	6.4.8. UID Command ............................................... 54
	6.5. Client Commands - Experimental/Expansion .................. 56
	6.5.1. X<atom> Command ........................................... 56
	7. Server Responses .......................................... 57
	7.1. Server Responses - Status Responses ....................... 58
	7.1.1. OK Response ............................................... 60
	7.1.2. NO Response ............................................... 60
	7.1.3. BAD Response .............................................. 61
	7.1.4. PREAUTH Response .......................................... 61
	7.1.5. BYE Response .............................................. 61
	7.2. Server Responses - Server and Mailbox Status .............. 62
	7.2.1. CAPABILITY Response ....................................... 62
	7.2.2. LIST Response ............................................. 63
	7.2.3. LSUB Response ............................................. 64
	7.2.4 STATUS Response ........................................... 65
	7.2.5. SEARCH Response ........................................... 65
	7.2.6. FLAGS Response ............................................ 65
	7.3. Server Responses - Mailbox Size ........................... 66
	7.3.1. EXISTS Response ........................................... 66
	7.3.2. RECENT Response ........................................... 66
	7.4. Server Responses - Message Status ......................... 67
	7.4.1. EXPUNGE Response .......................................... 67
	7.4.2. FETCH Response ............................................ 68
	7.5. Server Responses - Command Continuation Request ........... 73
	8. Sample IMAP4rev1 connection ............................... 75
	9. Formal Syntax ............................................. 76
	10. Author's Note ............................................. 87
	11. Security Considerations ................................... 87
	11.1. STARTTLS Security Considerations .......................... 87
	11.2. Other Security Considerations ............................. 88
	12. IANA Considerations ....................................... 89
	13. Author's Address .......................................... 89
	Appendices ........................................................ 90
	A. References ................................................ 90
	B. Changes from RFC 2060 ..................................... 92
	C. Key Word Index ............................................ 98
End of changes. 16 change blocks.
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