RFC 1730
Internet Message Access Protocol - Version 4
Network Working Group M. Crispin Request for Comments: 1730 University of Washington Category: Standards Track December 1994 INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4 Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract The Internet Message Access Protocol, Version 4 (IMAP4) allows a client to access and manipulate electronic mail messages on a server. IMAP4 permits manipulation of remote message folders, called "mailboxes", in a way that is functionally equivalent to local mailboxes. IMAP4 also provides the capability for an offline client to resynchronize with the server (see also [IMAP-DISC]). IMAP4 includes operations for creating, deleting, and renaming mailboxes; checking for new messages; permanently removing messages; setting and clearing flags; RFC 822 and MIME parsing; searching; and selective fetching of message attributes, texts, and portions thereof. Messages in IMAP4 are accessed by the use of numbers. These numbers are either message sequence numbers (relative position from 1 to the number of messages in the mailbox) or unique identifiers (immutable, strictly ascending values assigned to each message, but which are not necessarily contiguous). IMAP4 supports a single server. A mechanism for supporting multiple IMAP4 servers is discussed in [IMSP]. IMAP4 does not specify a means of posting mail; this function is handled by a mail transfer protocol such as [SMTP]. IMAP4 is designed to be upwards compatible from the [IMAP2] protocol. Compatibility issues are discussed in [IMAP-COMPAT].
Table of Contents IMAP4 Protocol Specification ...................................... 1 1. Organization of this Document ............................. 1 1.1. How to Read This Document ................................. 1 1.2. Conventions Used in this Document ......................... 1 2. Protocol Overview ......................................... 1 2.1. Link Level ................................................ 1 2.2. Commands and Responses .................................... 1 2.2.1. Client Protocol Sender and Server Protocol Receiver ....... 2 2.2.2. Server Protocol Sender and Client Protocol Receiver ....... 2 3. State and Flow Diagram .................................... 4 3.1. Non-Authenticated State ................................... 4 3.2. Authenticated State ....................................... 4 3.3. Selected State ............................................ 4 3.4. Logout State .............................................. 4 4. Data Formats .............................................. 6 4.1. Atom ...................................................... 6 4.2. Number .................................................... 6 4.3. String .................................................... 6 4.3.1. 8-bit and Binary Strings .................................. 7 4.4. Parenthesized List ........................................ 7 4.5. NIL ....................................................... 7 5. Operational Considerations ................................ 8 5.1. Mailbox Naming ............................................ 8 5.2. Mailbox Size and Message Status Updates ................... 8 5.3. Response when no Command in Progress ...................... 8 5.4. Autologout Timer .......................................... 9 5.5. Multiple Commands in Progress ............................. 9 6. Client Commands ........................................... 10 6.1. Client Commands - Any State ............................... 10 6.1.1. CAPABILITY Command ........................................ 10 6.1.2. NOOP Command .............................................. 11 6.1.3. LOGOUT Command ............................................ 11 6.2. Client Commands - Non-Authenticated State ................. 12 6.2.1. AUTHENTICATE Command ...................................... 12 6.2.2. LOGIN Command ............................................. 14 6.3. Client Commands - Authenticated State ..................... 14 6.3.1. SELECT Command ............................................ 15 6.3.2. EXAMINE Command ........................................... 16 6.3.3. CREATE Command ............................................ 17 6.3.4. DELETE Command ............................................ 18 6.3.5. RENAME Command ............................................ 18
6.3.6. SUBSCRIBE Command ......................................... 19 6.3.7. UNSUBSCRIBE Command ....................................... 19 6.3.8. LIST Command .............................................. 20 6.3.9. LSUB Command .............................................. 22 6.3.10. APPEND Command ............................................ 22 6.4. Client Commands - Selected State .......................... 23 6.4.1. CHECK Command ............................................. 23 6.4.2. CLOSE Command ............................................. 24 6.4.3. EXPUNGE Command ........................................... 25 6.4.4. SEARCH Command ............................................ 25 6.4.5. FETCH Command ............................................. 29 6.4.6. PARTIAL Command ........................................... 32 6.4.7. STORE Command ............................................. 33 6.4.8. COPY Command .............................................. 34 6.4.9. UID Command ............................................... 35 6.5. Client Commands - Experimental/Expansion .................. 37 6.5.1. X<atom> Command ........................................... 37 7. Server Responses .......................................... 38 7.1. Server Responses - Status Responses ....................... 39 7.1.1. OK Response ............................................... 40 7.1.2. NO Response ............................................... 40 7.1.3. BAD Response .............................................. 41 7.1.4. PREAUTH Response .......................................... 41 7.1.5. BYE Response .............................................. 41 7.2. Server Responses - Server and Mailbox Status .............. 42 7.2.1. CAPABILITY Response ....................................... 42 7.2.2. LIST Response ............................................. 43 7.2.3. LSUB Response ............................................. 44 7.2.4. SEARCH Response ........................................... 44 7.2.5. FLAGS Response ............................................ 44 7.3. Server Responses - Message Status ......................... 45 7.3.1. EXISTS Response ........................................... 45 7.3.2. RECENT Response ........................................... 45 7.3.3. EXPUNGE Response .......................................... 45 7.3.4. FETCH Response ............................................ 46 7.3.5. Obsolete Responses ........................................ 51 7.4. Server Responses - Command Continuation Request ........... 51 8. Sample IMAP4 session ...................................... 52 9. Formal Syntax ............................................. 53 10. Author's Note ............................................. 64 11. Security Considerations ................................... 64 12. Author's Address .......................................... 64 Appendices ........................................................ 65 A. Obsolete Commands ......................................... 65 A.6.3.OBS.1. FIND ALL.MAILBOXES Command ........................ 65 A.6.3.OBS.2. FIND MAILBOXES Command ............................ 65 A.6.3.OBS.3. SUBSCRIBE MAILBOX Command ......................... 66 A.6.3.OBS.4. UNSUBSCRIBE MAILBOX Command ....................... 66
B. Obsolete Responses ........................................ 68 B.7.2.OBS.1. MAILBOX Response .................................. 68 B.7.3.OBS.1. COPY Response ..................................... 68 B.7.3.OBS.2. STORE Response .................................... 69 C. References ................................................ 70 E. IMAP4 Keyword Index ....................................... 71
IMAP4 Protocol Specification 1. Organization of this Document 1.1. How to Read This Document This document is written from the point of view of the implementor of an IMAP4 client or server. Beyond the protocol overview in section 2, it is not optimized for someone trying to understand the operation of the protocol. The material in sections 3 through 5 provides the general context and definitions with which IMAP4 operates. Sections 6, 7, and 9 describe the IMAP commands, responses, and syntax, respectively. The relationships among these are such that it is almost impossible to understand any of them separately. In particular, one should not attempt to deduce command syntax from the command section alone; one should instead refer to the formal syntax section. 1.2. Conventions Used in this Document In examples, "C:" and "S:" indicate lines sent by the client and server respectively. 2. Protocol Overview 2.1. Link Level The IMAP4 protocol assumes a reliable data stream such as provided by TCP. When TCP is used, an IMAP4 server listens on port 143. 2.2. Commands and Responses An IMAP4 session consists of the establishment of a client/server connection, an initial greeting from the server, and client/server interactions. These client/server interactions consist of a client command, server data, and a server completion result response. All interactions transmitted by client and server are in the form of lines; that is, strings that end with a CRLF. The protocol receiver of an IMAP4 client or server is either reading a line, or is reading a sequence of octets with a known count followed by a line.
2.2.1. Client Protocol Sender and Server Protocol Receiver The client command begins an operation. Each client command is prefixed with a identifier (typically a short alphanumeric string, e.g. A0001, A0002, etc.) called a "tag". A different tag is generated by the client for each command. There are two cases in which a line from the client does not represent a complete command. In one case, a command argument is quoted with an octet count (see the description of literal in String under Data Formats); in the other case, the command arguments require server feedback (see the AUTHENTICATE command). In either case, the server sends a command continuation request response if it is ready for the octets (if appropriate) and the remainder of the command. This response is prefixed with the token "+". Note: If, instead, the server detected an error in the command, it sends a BAD completion response with tag matching the command (as described below) to reject the command and prevent the client from sending any more of the command. It is also possible for the server to send a completion response for some other command (if multiple commands are in progress), or untagged data. In either case, the command continuation request is still pending; the client takes the appropriate action for the response, and reads another response from the server. The protocol receiver of an IMAP4 server reads a command line from the client, parses the command and its arguments, and transmits server data and a server command completion result response. 2.2.2. Server Protocol Sender and Client Protocol Receiver Data transmitted by the server to the client and status responses that do not indicate command completion are prefixed with the token "*", and are called untagged responses. Server data may be sent as a result of a client command, or may be sent unilaterally by the server. There is no syntactic difference between server data that resulted from a specific command and server data that were sent unilaterally. The server completion result response indicates the success or failure of the operation. It is tagged with the same tag as the client command which began the operation. Thus, if more than one
command is in progress, the tag in a server completion response identifies the command to which the response applies. There are three possible server completion responses: OK (indicating success), NO (indicating failure), or BAD (indicating protocol error such as unrecognized command or command syntax error). The protocol receiver of an IMAP4 client reads a response line from the server. It then takes action on the response based upon the first token of the response, which may be a tag, a "*", or a "+". As described above. A client MUST be prepared to accept any server response at all times. This includes server data that it may not have requested. Server data SHOULD be recorded, so that the client can reference its recorded copy rather than sending a command to the server to request the data. In the case of certain server data, recording the data is mandatory. This topic is discussed in greater detail in the Server Responses section.
3. State and Flow Diagram An IMAP4 server is in one of four states. Most commands are valid in only certain states. It is a protocol error for the client to attempt a command while the command is in an inappropriate state. In this case, a server will respond with a BAD or NO (depending upon server implementation) command completion result. 3.1. Non-Authenticated State In non-authenticated state, the user must supply authentication credentials before most commands will be permitted. This state is entered when a connection starts unless the connection has been pre-authenticated. 3.2. Authenticated State In authenticated state, the user is authenticated and must select a mailbox to access before commands that affect messages will be permitted. This state is entered when a pre-authenticated connection starts, when acceptable authentication credentials have been provided, or after an error in selecting a mailbox. 3.3. Selected State In selected state, a mailbox has been selected to access. This state is entered when a mailbox has been successfully selected. 3.4. Logout State In logout state, the session is being terminated, and the server will close the connection. This state can be entered as a result of a client request or by unilateral server decision.
+--------------------------------------+
|initial connection and server greeting|
+--------------------------------------+
|| (1) || (2) || (3)
VV || ||
+-----------------+ || ||
|non-authenticated| || ||
+-----------------+ || ||
|| (7) || (4) || ||
|| VV VV ||
|| +----------------+ ||
|| | authenticated |<=++ ||
|| +----------------+ || ||
|| || (7) || (5) || (6) ||
|| || VV || ||
|| || +--------+ || ||
|| || |selected|==++ ||
|| || +--------+ ||
|| || || (7) ||
VV VV VV VV
+--------------------------------------+
| logout and close connection |
+--------------------------------------+
(1) connection without pre-authentication (OK greeting)
(2) pre-authenticated connection (PREAUTH greeting)
(3) rejected connection (BYE greeting)
(4) successful LOGIN or AUTHENTICATE command
(5) successful SELECT or EXAMINE command
(6) CLOSE command, or failed SELECT or EXAMINE command
(7) LOGOUT command, server shutdown, or connection closed
4. Data Formats IMAP4 uses textual commands and responses. Data in IMAP4 can be in one of several forms: atom, number, string, parenthesized list, or NIL. 4.1. Atom An atom consists of one or more non-special characters. 4.2. Number A number consists of one or more digit characters, and represents a numeric value. 4.3. String A string is in one of two forms: literal and quoted string. The literal form is the general form of string. The quoted string form is an alternative that avoids the overhead of processing a literal at the cost of restrictions of what may be in a quoted string. A literal is a sequence of zero or more octets (including CR and LF), prefix-quoted with an octet count in the form of an open brace ("{"), the number of octets, close brace ("}"), and CRLF. In the case of literals transmitted from server to client, the CRLF is immediately followed by the octet data. In the case of literals transmitted from client to server, the client must wait to receive a command continuation request (described later in this document) before sending the octet data (and the remainder of the command). A quoted string is a sequence of zero or more 7-bit characters, excluding CR and LF, with double quote (<">) characters at each end. The empty string is respresented as either "" (a quoted string with zero characters between double quotes) or as {0} followed by CRLF (a literal with an octet count of 0). Note: Even if the octet count is 0, a client transmitting a literal must wait to receive a command continuation request.
4.3.1. 8-bit and Binary Strings 8-bit textual and binary mail is supported through the use of [MIME-1] encoding. IMAP4 implementations MAY transmit 8-bit or multi-octet characters in literals, but should do so only when the character set is identified. Although a BINARY body encoding is defined, unencoded binary strings are not permitted. A "binary string" is any string with NUL characters. Implementations MUST encode binary data into a textual form such as BASE64 before transmitting the data. A string with an excessive amount of CTL characters may also be considered to be binary, although this is not required. 4.4. Parenthesized List Data structures are represented as a "parenthesized list"; a sequence of data items, delimited by space, and bounded at each end by parentheses. A parenthesized list may itself contain other parenthesized lists, using multiple levels of parentheses to indicate nesting. The empty list is represented as () -- a parenthesized list with no members. 4.5. NIL The special atom "NIL" represents the non-existence of a particular data item that is represented as a string or parenthesized list, as distinct from the empty string "" or the empty parenthesized list ().
5. Operational Considerations 5.1. Mailbox Naming The interpretation of mailbox names is implementation-dependent. However, the mailbox name INBOX is a special name reserved to mean "the primary mailbox for this user on this server". If it is desired to export hierarchical mailbox names, mailbox names must be left-to-right hierarchical using a single character to separate levels of hierarchy. The same hierarchy separator character is used for all levels of hierarchy within a single name. 5.2. Mailbox Size and Message Status Updates At any time, a server can send data that the client did not request. Sometimes, such behavior is required. For example, agents other than the server may add messages to the mailbox (e.g. new mail delivery), change the flags of message in the mailbox (e.g. simultaneous access to the same mailbox by multiple agents), or even remove messages from the mailbox. A server MUST send mailbox size updates automatically if a mailbox size change is observed during the processing of a command. A server SHOULD send message flag updates automatically, without requiring the client to request such updates explicitly. Special rules exist for server notification of a client about the removal of messages to prevent synchronization errors; see the description of the EXPUNGE response for more details. Regardless of what implementation decisions a client may take on remembering data from the server, a client implementation MUST record mailbox size updates. It MUST NOT assume that any command after initial mailbox selection will return the size of the mailbox. 5.3. Response when no Command in Progress Server implementations are permitted to send an untagged response (except for EXPUNGE) while there is no command in progress. Server implementations that send such responses MUST deal with flow control considerations. Specifically, they must either (1) verify that the size of the data does not exceed the underlying transport's available window size, or (2) use non-blocking writes.
5.4. Autologout Timer If a server has an inactivity autologout timer, that timer MUST be of at least 30 minutes' duration. The receipt of ANY command from the client during that interval should suffice to reset the autologout timer. 5.5. Multiple Commands in Progress The client is not required to wait for the completion result response of a command before sending another command, subject to flow control constraints on the underlying data stream. Similarly, a server is not required to process a command to completion before beginning processing of the next command, unless an ambiguity would result because of a command that would affect the results of other commands. If there is such an ambiguity, the server executes commands to completion in the order given by the client.
6. Client Commands IMAP4 commands are described in this section. Commands are organized by the state in which the command is permitted. Commands which are permitted in multiple states are listed in the minimum permitted state (for example, commands valid in authenticated and selected state are listed in the authenticated state commands). Command arguments, identified by "Arguments:" in the command descriptions below, are described by function, not by syntax. The precise syntax of command arguments is described in the Formal Syntax section. Some commands cause specific server data to be returned; these are identified by "Data:" in the command descriptions below. See the response descriptions in the Responses section for information on these responses, and the Formal Syntax section for the precise syntax of these responses. It is possible for server data to be transmitted as a result of any command; thus, commands that do not specifically require server data specify "no specific data for this command" instead of "none". The "Result:" in the command description refers to the possible tagged status responses to a command, and any special interpretation of these status responses. 6.1. Client Commands - Any State The following commands are valid in any state: CAPABILITY, NOOP, and LOGOUT. 6.1.1. CAPABILITY Command Arguments: none Data: mandatory untagged response: CAPABILITY Result: OK - capability completed BAD - command unknown or arguments invalid The CAPABILITY command requests a listing of capabilities that the server supports. The server MUST send a single untagged CAPABILITY response with "IMAP4" as the first listed capability before the (tagged) OK response. This listing of capabilities is not dependent upon connection state or user. It is therefore not necessary to issue a CAPABILITY command more than once in a session.
Capability names other than "IMAP4" refer to extensions,
revisions, or amendments to this specification. See the
documentation of the CAPABILITY response for additional
information. No capabilities are enabled without explicit client
action to invoke the capability. See the section entitled "Client
Commands - Experimental/Expansion" for information about the form
of site or implementation-specific capabilities.
Example: C: abcd CAPABILITY
S: * CAPABILITY IMAP4
S: abcd OK CAPABILITY completed
6.1.2. NOOP Command
Arguments: none
Data: no specific data for this command (but see below)
Result: OK - noop completed
BAD - command unknown or arguments invalid
The NOOP command always succeeds. It does nothing.
Since any command can return a status update as untagged data, the
NOOP command can be used as a periodic poll for new messages or
message status updates during a period of inactivity. The NOOP
command can also be used to reset any inactivity autologout timer
on the server.
Example: C: a002 NOOP
S: a002 OK NOOP completed
. . .
C: a047 NOOP
S: * 22 EXPUNGE
S: * 23 EXISTS
S: * 3 RECENT
S: * 14 FETCH (FLAGS (\Seen \Deleted))
S: a047 OK NOOP completed
6.1.3. LOGOUT Command Arguments: none Data: mandatory untagged response: BYE Result: OK - logout completed BAD - command unknown or arguments invalid The LOGOUT command informs the server that the client is done with the session. The server must send a BYE untagged response before the (tagged) OK response, and then close the network connection. Example: C: A023 LOGOUT S: * BYE IMAP4 Server logging out S: A023 OK LOGOUT completed (Server and client then close the connection) 6.2. Client Commands - Non-Authenticated State In non-authenticated state, the AUTHENTICATE or LOGIN command establishes authentication and enter authenticated state. The AUTHENTICATE command provides a general mechanism for a variety of authentication techniques, whereas the LOGIN command uses the traditional user name and plaintext password pair. Server implementations may allow non-authenticated access to certain mailboxes. The convention is to use a LOGIN command with the userid "anonymous". A password is required. It is implementation-dependent what requirements, if any, are placed on the password and what access restrictions are placed on anonymous users. Once authenticated (including as anonymous), it is not possible to re-enter non-authenticated state. In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), the following commands are valid in non-authenticated state: AUTHENTICATE and LOGIN.
6.2.1. AUTHENTICATE Command Arguments: authentication mechanism name Data: continuation data may be requested Result: OK - authenticate completed, now in authenticated state NO - authenticate failure: unsupported authentication mechanism, credentials rejected BAD - command unknown or arguments invalid, authentication exchange cancelled The AUTHENTICATE command indicates an authentication mechanism, such as described in [IMAP-AUTH], to the server. If the server supports the requested authentication mechanism, it performs an authentication protocol exchange to authenticate and identify the user. Optionally, it also negotiates a protection mechanism for subsequent protocol interactions. If the requested authentication mechanism is not supported, the server should reject the AUTHENTICATE command by sending a tagged NO response. The authentication protocol exchange consists of a series of server challenges and client answers that are specific to the authentication mechanism. A server challenge consists of a command continuation request response with the "+" token followed by a BASE64 encoded string. The client answer consists of a line consisting of a BASE64 encoded string. If the client wishes to cancel an authentication exchange, it should issue a line with a single "*". If the server receives such an answer, it must reject the AUTHENTICATE command by sending a tagged BAD response. A protection mechanism provides integrity and privacy protection to the protocol session. If a protection mechanism is negotiated, it is applied to all subsequent data sent over the connection. The protection mechanism takes effect immediately following the CRLF that concludes the authentication exchange for the client, and the CRLF of the tagged OK response for the server. Once the protection mechanism is in effect, the stream of command and response octets is processed into buffers of ciphertext. Each buffer is transferred over the connection as a stream of octets prepended with a four octet field in network byte order that represents the length of the following data. The maximum ciphertext buffer length is defined by the protection mechanism. The server is not required to support any particular authentication mechanism, nor are authentication mechanisms required to support any protection mechanisms. If an AUTHENTICATE command fails with a NO response, the client may try another
authentication mechanism by issuing another AUTHENTICATE command,
or may attempt to authenticate by using the LOGIN command. In
other words, the client may request authentication types in
decreasing order of preference, with the LOGIN command as a last
resort.
Example: S: * OK KerberosV4 IMAP4 Server
C: A001 AUTHENTICATE KERBEROS_V4
S: + AmFYig==
C: BAcAQU5EUkVXLkNNVS5FRFUAOCAsho84kLN3/IJmrMG+25a4DT
+nZImJjnTNHJUtxAA+o0KPKfHEcAFs9a3CL5Oebe/ydHJUwYFd
WwuQ1MWiy6IesKvjL5rL9WjXUb9MwT9bpObYLGOKi1Qh
S: + or//EoAADZI=
C: DiAF5A4gA+oOIALuBkAAmw==
S: A001 OK Kerberos V4 authentication successful
Note: the line breaks in the first client answer are for
editorial clarity and are not in real authenticators.
6.2.2. LOGIN Command
Arguments: user name
password
Data: no specific data for this command
Result: OK - login completed, now in authenticated state
NO - login failure: user name or password rejected
BAD - command unknown or arguments invalid
The LOGIN command identifies the user to the server and carries
the plaintext password authenticating this user.
Example: C: a001 LOGIN SMITH SESAME
S: a001 OK LOGIN completed
6.3. Client Commands - Authenticated State
In authenticated state, commands that manipulate mailboxes as atomic
entities are permitted. Of these commands, the SELECT and EXAMINE
commands will select a mailbox for access and enter selected state.
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), the following commands are valid in authenticated state: SELECT, EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, and APPEND. 6.3.1. SELECT Command Arguments: mailbox name Data: mandatory untagged responses: FLAGS, EXISTS, RECENT optional OK untagged responses: UNSEEN, PERMANENTFLAGS Result: OK - select completed, now in selected state NO - select failure, now in authenticated state: no such mailbox, can't access mailbox BAD - command unknown or arguments invalid The SELECT command selects a mailbox so that messages in the mailbox can be accessed. Before returning an OK to the client, the server MUST send the following untagged data to the client: FLAGS Defined flags in the mailbox <n> EXISTS The number of messages in the mailbox <n> RECENT The number of messages added to the mailbox since the previous time this mailbox was read OK [UIDVALIDITY <n>] The unique identifier validity value. See the description of the UID command for more detail. to define the initial state of the mailbox at the client. If it is not possible to determine the messages that were added since the previous time a mailbox was read, then all messages SHOULD be considered recent. The server SHOULD also send an UNSEEN response code in an OK untagged response, indicating the message sequence number of the first unseen message in the mailbox. If the client can not change the permanent state of one or more of the flags listed in the FLAGS untagged response, the server SHOULD send a PERMANENTFLAGS response code in an OK untagged response, listing the flags that the client may change permanently. Only one mailbox may be selected at a time in a session; simultaneous access to multiple mailboxes requires multiple
sessions. The SELECT command automatically deselects any
currently selected mailbox before attempting the new selection.
Consequently, if a mailbox is selected and a SELECT command that
fails is attempted, no mailbox is selected.
If the user is permitted to modify the mailbox, the server SHOULD
prefix the text of the tagged OK response with the "[READ-WRITE]"
response code.
If the user is not permitted to modify the mailbox but is
permitted read access, the mailbox is selected as read-only, and
the server MUST prefix the text of the tagged OK response to
SELECT with the "[READ-ONLY]" response code. Read-only access
through SELECT differs from the EXAMINE command in that certain
read-only mailboxes may permit the change of permanent state on a
per-user (as opposed to global) basis. Netnews messages marked in
a user's .newsrc file are an example of such per-user permanent
state that can be modified with read-only mailboxes.
Example: C: A142 SELECT INBOX
S: * 172 EXISTS
S: * 1 RECENT
S: * OK [UNSEEN 12] Message 12 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
S: A142 OK [READ-WRITE] SELECT completed
6.3.2. EXAMINE Command
Arguments: mailbox name
Data: mandatory untagged responses: FLAGS, EXISTS, RECENT
optional OK untagged responses: UNSEEN, PERMANENTFLAGS
Result: OK - examine completed, now in selected state
NO - examine failure, now in authenticated state: no
such mailbox, can't access mailbox
BAD - command unknown or arguments invalid
The EXAMINE command is identical to SELECT and returns the same
output; however, the selected mailbox is identified as read-only.
No changes to the permanent state of the mailbox, including
per-user state, are permitted.
The text of the tagged OK response to the EXAMINE command MUST
begin with the "[READ-ONLY]" response code.
Example: C: A932 EXAMINE blurdybloop
S: * 17 EXISTS
S: * 2 RECENT
S: * OK [UNSEEN 8] Message 8 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
S: A932 OK [READ-ONLY] EXAMINE completed
6.3.3. CREATE Command
Arguments: mailbox name
Data: no specific data for this command
Result: OK - create completed
NO - create failure: can't create mailbox with that name
BAD - command unknown or arguments invalid
The CREATE command creates a mailbox with the given name. An OK
response is returned only if a new mailbox with that name has been
created. It is an error to attempt to create INBOX or a mailbox
with a name that refers to an extant mailbox. Any error in
creation will return a tagged NO response.
If the mailbox name is suffixed with the server's hierarchy
separator character (as returned from the server by a LIST
command), this is a declaration that the client may, in the
future, create mailbox names under this name in the hierarchy.
Server implementations that do not require this declaration MUST
ignore it.
If a new mailbox is created with the same name as a mailbox which
was deleted, its unique identifiers MUST be greater than any
unique identifiers used in the previous incarnation of the mailbox
UNLESS the new incarnation has a different unique identifier
validity value. See the description of the UID command for more
detail.
Example: C: A003 CREATE owatagusiam/
S: A003 OK CREATE completed
C: A004 CREATE owatagusiam/blurdybloop
S: A004 OK CREATE completed
Note: the interpretation of this example depends on whether
"/" was returned as the hierarchy separator from LIST. If
"/" is the hierarchy separator, a new level of hierarchy
named "owatagusiam" with a member called "blurdybloop" is
created. Otherwise, two mailboxes at the same hierarchy
level are created.
6.3.4. DELETE Command
Arguments: mailbox name
Data: no specific data for this command
Result: OK - delete completed
NO - delete failure: can't delete mailbox with that name
BAD - command unknown or arguments invalid
The DELETE command permanently removes the mailbox with the given
name. A tagged OK response is returned only if the mailbox has
been deleted. It is an error to attempt to delete INBOX or a
mailbox name that does not exist. Any error in deletion will
return a tagged NO response.
The value of the highest-used unique indentifier of the deleted
mailbox MUST be preserved so that a new mailbox created with the
same name will not reuse the identifiers of the former
incarnation, UNLESS the new incarnation has a different unique
identifier validity value. See the description of the UID command
for more detail.
Example: C: A683 DELETE blurdybloop
S: A683 OK DELETE completed
6.3.5. RENAME Command
Arguments: existing mailbox name
new mailbox name
Data: no specific data for this command
Result: OK - rename completed
NO - rename failure: can't rename mailbox with that name,
can't rename to mailbox with that name
BAD - command unknown or arguments invalid
The RENAME command changes the name of a mailbox. A tagged OK
response is returned only if the mailbox has been renamed. It is
an error to attempt to rename from a mailbox name that does not
exist or to a mailbox name that already exists. Any error in
renaming will return a tagged NO response.
Renaming INBOX is permitted; a new, empty INBOX is created in its
place.
Example: C: Z4S9 RENAME blurdybloop owatagusiam
S: Z4S9 OK RENAME completed
6.3.6. SUBSCRIBE Command
Arguments: mailbox
Data: no specific data for this command
Result: OK - subscribe completed
NO - subscribe failure: can't subscribe to that name
BAD - command unknown or arguments invalid
The SUBSCRIBE command adds the specified mailbox name to the
server's set of "active" or "subscribed" mailboxes as returned by
the LSUB command. This command returns a tagged OK response only
if the subscription is successful.
Example: C: A002 SUBSCRIBE #news.comp.mail.mime
S: A002 OK SUBSCRIBE completed
6.3.7. UNSUBSCRIBE Command
Arguments: mailbox name
Data: no specific data for this command
Result: OK - unsubscribe completed
NO - unsubscribe failure: can't unsubscribe that name
BAD - command unknown or arguments invalid
The UNSUBSCRIBE command removes the specified mailbox name from
the server's set of "active" or "subscribed" mailboxes as returned
by the LSUB command. This command returns a tagged OK response
only if the unsubscription is successful.
Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime
S: A002 OK UNSUBSCRIBE completed
6.3.8. LIST Command
Arguments: reference name
mailbox name with possible wildcards
Data: untagged responses: LIST
Result: OK - list completed
NO - list failure: can't list that reference or name
BAD - command unknown or arguments invalid
The LIST command returns a subset of names from the complete set
of all names available to the user. Zero or more untagged LIST
replies are returned, containing the name attributes, hierarchy
delimiter, and name; see the description of the LIST reply for
more detail.
An empty ("" string) reference name argument indicates that the
mailbox name is interpreted as by SELECT. The returned mailbox
names MUST match the supplied mailbox name pattern. A non-empty
reference name argument is the name of a mailbox or a level of
mailbox hierarchy, and indicates a context in which the mailbox
name is interpreted in an implementation-defined manner.
The reference and mailbox name arguments are interpreted, in an
implementation-dependent fashion, into a canonical form that
represents an unambiguous left-to-right hierarchy. The returned
mailbox names will be in the interpreted form.
Any part of the reference argument that is included in the
interpreted form SHOULD prefix the interpreted form. It should
also be in the same form as the reference name argument. This
rule permits the client to determine if the returned mailbox name
is in the context of the reference argument, or if something about
the mailbox argument overrode the reference argument. Without
this rule, the client would have to have knowledge of the server's
naming semantics including what characters are "breakouts" that
override a naming context.
For example, here are some examples of how references
and mailbox names might be interpreted on a UNIX-based
server:
Reference Mailbox Name Interpretation
------------ ------------ --------------
~smith/Mail/ foo.* ~smith/Mail/foo.*
archive/ % archive/%
#news. comp.mail.* #news.comp.mail.*
~smith/Mail/ /usr/doc/foo /usr/doc/foo
archive/ ~fred/Mail/* ~fred/Mail/*
The first three examples demonstrate interpretations in
the context of the reference argument. Note that
"~smith/Mail" should not be transformed into something
like "/u2/users/smith/Mail", or it would be impossible
for the client to determine that the interpretation was
in the context of the reference.
The character "*" is a wildcard, and matches zero or more
characters at this position. The character "%" is similar to "*",
but it does not match a hierarchy delimiter. If the "%" wildcard
is the last character of a mailbox name argument, matching levels
of hierarchy are also returned. If these levels of hierarchy are
not also selectable mailboxes, they are returned with the
\Noselect mailbox name attribute (see the description of the LIST
response for more detail).
Server implementations are permitted to "hide" otherwise
accessible mailboxes from the wildcard characters, by preventing
certain characters or names from matching a wildcard in certain
situations. For example, a UNIX-based server might restrict the
interpretation of "*" so that an initial "/" character does not
match.
The special name INBOX is included in the output from LIST if it
matches the input arguments and INBOX is supported by this server
for this user. The criteria for omitting INBOX is whether SELECT
INBOX will return failure; it is not relevant whether the user's
real INBOX resides on this or some other server.
Example: C: A002 LIST "~/Mail/" "%"
S: * LIST (\Noselect) "/" ~/Mail/foo
S: * LIST () "/" ~/Mail/meetings
S: A002 OK LIST completed
6.3.9. LSUB Command Arguments: reference name mailbox name with possible wildcards Data: untagged responses: LSUB Result: OK - lsub completed NO - lsub failure: can't list that reference or name BAD - command unknown or arguments invalid The LSUB command returns a subset of names from the set of names that the user has declared as being "active" or "subscribed". Zero or more untagged LSUB replies are returned. The arguments to LSUB are in the same form as those for LIST. Example: C: A002 LSUB "#news." "comp.mail.*" S: * LSUB () "." #news.comp.mail.mime S: * LSUB () "." #news.comp.mail.misc S: A002 OK LSUB completed 6.3.10. APPEND Command Arguments: mailbox name optional flag parenthesized list optional date/time string message literal Data: no specific data for this command Result: OK - append completed NO - append error: can't append to that mailbox, error in flags or date/time or message text BAD - command unknown or arguments invalid The APPEND command appends the literal argument as a new message in the specified destination mailbox. This argument is in the format of an [RFC-822] message. 8-bit characters are permitted in the message. A server implementation that is unable to preserve 8-bit data properly MUST be able to reversibly convert 8-bit APPEND data to 7-bit using [MIME-1] encoding. If a flag parenthesized list or date_time are specified, that data SHOULD be set in the resulting message; otherwise, the defaults of empty flags and the current date/time are used.
If the append is unsuccessful for any reason, the mailbox MUST be
restored to its state before the APPEND attempt; no partial
appending is permitted. If the mailbox is currently selected, the
normal new mail actions should occur.
If the destination mailbox does not exist, a server MUST return an
error, and MUST NOT automatically create the mailbox. Unless it
is certain that the destination mailbox can not be created, the
server MUST send the response code "[TRYCREATE]" as the prefix of
the text of the tagged NO response. This gives a hint to the
client that it can attempt a CREATE command and retry the APPEND
if the CREATE is successful.
Example: C: A003 APPEND saved-messages (\Seen) {310}
C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
C: From: Fred Foobar <foobar@Blurdybloop.COM>
C: Subject: afternoon meeting
C: To: mooch@owatagu.siam.edu
C: Message-Id: <B27397-0100000@Blurdybloop.COM>
C: MIME-Version: 1.0
C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
C:
C: Hello Joe, do you think we can meet at 3:30 tomorrow?
C:
S: A003 OK APPEND completed
Note: the APPEND command is not used for message delivery,
because it does not provide a mechanism to transfer [SMTP]
envelope information.
(page 27 continued on part 2)
