Network Working Group M. Crispin Internet Draft: IMAP4 University of Washington Document: internet-drafts/draft-ietf-imap-imap4-03.txt June 1994 INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4 Status of this Memo This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress". To learn the current status of any Internet-Draft, please check the id-abstracts.txt listing contained in the Internet-Drafts Shadow Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or munnari.oz.au. This is a draft document of the IETF IMAP Working Group. A revised version of this draft document will be submitted to the RFC editor as a Proposed Standard for the Internet Community. Discussion and suggestions for improvement are requested, and should be sent to imap@CAC.Washington.EDU. This document will expire before 31 November 1994. Distribution of this draft is unlimited. Abstract The Internet Message Access Protocol, Version 4 (IMAP4) allows a client to access and manipulate electronic mail messages on a server. IMAP4 permits manipulation of remote message folders, called "mailboxes", in a way that is functionally equivalent to local mailboxes. IMAP4 also provides the capability for an offline client to resynchronize with the server. IMAP4 includes operations for creating, deleting, and renaming mailboxes; checking for new messages; permanently removing messages; setting and clearing flags; RFC 822 and MIME parsing; searching; and selective fetching of message attributes, texts, and portions thereof. Messages in IMAP4 are accessed by a set of either sequence Crispin [Page i] Internet DRAFT IMAP4 June 20, 1994 numbers (relative position from 1 to the number of messages in the mailbox) or immutable unique identifiers. IMAP4 does not specify a means of posting mail; this function is handled by a mail transfer protocol such as SMTP (RFC 821). IMAP4 is designed to be upwards compatible from the IMAP2 protocol described in RFC 1176. Conventions Used in this Document In examples, "C:" and "S:" indicate lines sent by the client and server respectively. Crispin [Page ii] Internet DRAFT IMAP4 June 20, 1994 Table of Contents Status of this Memo ............................................... i Abstract .......................................................... i Conventions Used in this Document ................................. ii IMAP4 Protocol Specification ...................................... 1 1. Protocol Overview ......................................... 1 2. State and Flow Diagram .................................... 2 2.1. Non-Authenticated State ................................... 2 2.2. Authenticated State ....................................... 2 2.3. Selected State ............................................ 2 2.4. Logout State .............................................. 2 3. Data Formats .............................................. 4 3.1. Atom, String, Number, NIL ................................. 4 3.2. Parenthesized List ........................................ 4 3.3. 8-bit Data ................................................ 4 3.4. Binary Data ............................................... 4 4. Operational Considerations ................................ 5 4.1. Mailbox Size and Message Status Updates ................... 5 4.2. Response when no Command in Progress ...................... 5 4.3. Autologout Timer .......................................... 5 5. Client Commands ........................................... 6 5.1. Client Commands - Any State ............................... 6 5.1.1. CAPABILITY Command ........................................ 6 5.1.2. NOOP Command .............................................. 6 5.1.3. LOGOUT Command ............................................ 7 5.2. Client Commands - Non-Authenticated State ................. 7 5.2.1. AUTHENTICATE Command ...................................... 8 5.2.2. LOGIN Command ............................................. 9 5.3. Client Commands - Authenticated State ..................... 9 5.3.1. SELECT Command ............................................ 10 5.3.2. EXAMINE Command ........................................... 11 5.3.3. CREATE Command ............................................ 12 5.3.4. DELETE Command ............................................ 12 5.3.5. RENAME Command ............................................ 13 5.3.6. SUBSCRIBE Command ......................................... 14 5.3.7. UNSUBSCRIBE Command ....................................... 14 5.3.8. LIST Command .............................................. 14 5.3.9. LSUB Command .............................................. 16 5.3.10. FIND ALL.MAILBOXES Command ................................ 16 5.3.11. FIND MAILBOXES Command .................................... 17 5.3.12. APPEND Command ............................................ 18 5.4. Client Commands - Selected State .......................... 19 Crispin [Page iii] Internet DRAFT IMAP4 June 20, 1994 5.4.1. CHECK Command ............................................. 19 5.4.2. CLOSE Command ............................................. 20 5.4.3. EXPUNGE Command ........................................... 20 5.4.4. SEARCH Command ............................................ 21 5.4.5. FETCH Command ............................................. 25 5.4.6. PARTIAL Command ........................................... 28 5.4.7. STORE Command ............................................. 29 5.4.8. COPY Command .............................................. 30 5.4.9. UID Command ............................................... 31 5.5. Client Commands - Experimental/Expansion .................. 32 5.5.1. X Command ........................................... 32 6. Server Responses .......................................... 33 6.1. Server Responses - Status Responses ....................... 33 6.1.1. OK Response ............................................... 34 6.1.2. NO Response ............................................... 35 6.1.3. BAD Response .............................................. 35 6.1.4. PREAUTH Response .......................................... 36 6.1.5. BYE Response .............................................. 36 6.2. Server Responses - Server and Mailbox Status .............. 36 6.2.1. CAPABILITY Response ....................................... 37 6.2.2. LIST Response ............................................. 37 6.2.3. LSUB Response ............................................. 38 6.2.4. MAILBOX Response .......................................... 38 6.2.5. SEARCH Response ........................................... 39 6.2.6. FLAGS Response ............................................ 39 6.3. Server Responses - Message Status ......................... 39 6.3.1. EXISTS Response ........................................... 40 6.3.2. RECENT Response ........................................... 40 6.3.3. EXPUNGE Response .......................................... 40 6.3.4. FETCH Response ............................................ 40 6.3.5. COPY Response ............................................. 45 6.3.6. STORE Response ............................................ 45 6.4. Server Responses - Command Continuation Request ........... 46 7. Sample IMAP4 session ...................................... 47 8. Formal Syntax ............................................. 48 Appendices ........................................................ 58 A. Author's Note ............................................. 58 B. Security Considerations ................................... 58 C. Author's Address .......................................... 58 D. IMAP4 Keyword Index ....................................... 59 Crispin [Page iv] IMAP4 Protocol Specification 1. Protocol Overview The IMAP4 protocol assumes a reliable data stream such as provided by TCP. When TCP is used, an IMAP4 server listens on port 143. An IMAP4 session consists of the establishment of a client/server connection, an initial greeting from the server, and client/server interactions. These client/server interactions consist of a client command, server data, and a server completion result response. The client command begins an operation and the server completion result response indicates the success or failure of the operation. Each client command is prefixed with a identifier (typically a short alphanumeric string, e.g. A0001, A0002, etc.) called a "tag". A different tag is generated by the client for each command. This tag is repeated as the prefix of the server completion result response, and identifies the command to which the response applies. Server responses that are not related to the completion of a command are untagged. This includes data transmitted by the server to the client, and is discussed in greater detail in the Server Responses section. The client is not required to wait for the completion result response of a command before sending another command, subject to flow control constraints on the underlying data stream. Similarly, a server is not required to process a command to completion before beginning processing of the next command, unless an ambiguity would result because of a command that would affect the results of other commands. If there is such an ambiguity, the server executes commands to completion in the order given by the client. Command and response arguments are described by function. The precise syntax of command and response arguments is described in the Formal Syntax section. Crispin [Page 1] Internet DRAFT IMAP4 June 20, 1994 2. State and Flow Diagram An IMAP4 server is in one of four states: 2.1. Non-Authenticated State In non-authenticated state, the user must supply authentication credentials before most commands will be permitted. This state is entered when a connection starts unless the connection has been pre- authenticated. 2.2. Authenticated State In authenticated state, the user is authenticated and must select a mailbox to access before commands that affect messages will be permitted. This state is entered when a pre-authenticated connection starts, when acceptable authentication credentials have been provided, or after an error in selecting a mailbox. 2.3. Selected State In selected state, a mailbox has been selected to access. This state is entered when a mailbox has been successfully selected. 2.4. Logout State In logout state, the session is being terminated, and the server will close the connection. This state can be entered as a result of a client request or by unilateral server decision. Crispin [Page 2] Internet DRAFT IMAP4 June 20, 1994 +--------------------------------------+ |initial connection and server greeting| +--------------------------------------+ || (1) || (2) || (3) VV || || +-----------------+ || || |non-authenticated| || || +-----------------+ || || || (7) || (4) || || || VV VV || || +----------------+ || || | authenticated |<=++ || || +----------------+ || || || || (7) || (5) || (6) || || || VV || || || || +--------+ || || || || |selected|==++ || || || +--------+ || || || || (7) || VV VV VV VV +--------------------------------------+ | logout and close connection | +--------------------------------------+ (1) connection without pre-authentication (OK greeting) (2) pre-authenticated connection (PREAUTH greeting) (3) rejected connection (BYE greeting) (4) successful LOGIN or AUTHENTICATE command (5) successful SELECT or EXAMINE command (6) CLOSE command, or failed SELECT or EXAMINE command (7) LOGOUT command, server shutdown, or connection closed Crispin [Page 3] Internet DRAFT IMAP4 June 20, 1994 3. Data Formats IMAP4 uses textual commands and responses. 3.1. Atom, String, Number, NIL Individual data items in IMAP4 are represented as atoms (one or more non-special characters), strings (a quoted sequence of characters), or numbers. Some data items may be either atoms or strings. The atom "NIL" represents the non-existence of a data item, as distinct from the empty string "" or the empty list (). 3.2. Parenthesized List Data structures are represented as a "parenthesized list"; a sequence of data items, delimited by space, and bounded at each end by parentheses. A parenthesized list may itself contain other parenthesized lists, using multiple levels of parentheses to indicate nesting. This is similar to the S-expression syntax of the Lisp programming language. 3.3. 8-bit Data 8-bit textual and binary mail is supported through the use of MIME encoding. IMAP4 implementations MAY transmit 8-bit or multi-octet characters in literals, but should do so only when the character set is identified. 3.4. Binary Data Although a BINARY body encoding is defined, unencoded binary strings are not permitted. A "binary string" is any string with NUL characters. Implementations MUST encode binary data into a textual form such as BASE64 before transmitting the data. A string with an excessive amount of CTL characters may also be considered to be binary, although this is not required. Crispin [Page 4] Internet DRAFT IMAP4 June 20, 1994 4. Operational Considerations 4.1. Mailbox Size and Message Status Updates At any time, a server can send data that the client did not request. Sometimes, such behavior is required. A server MUST send mailbox size updates automatically if a mailbox size change is observed during the processing of a command. A server SHOULD send message flag updates automatically, without requiring the client to request such updates explicitly. Regardless of what implementation decisions a client may take on remembering data from the server, a client implementation MUST record mailbox size updates. It MUST NOT assume that any command after initial mailbox selection will return the size of the mailbox. 4.2. Response when no Command in Progress Server implementations are permitted to send an untagged response (except for EXPUNGE) while there is no command in progress. Server implementations that send such responses MUST deal with flow control considerations. Specifically, they must either (1) verify that the size of the data does not exceed the underlying transport's available window size, or (2) use non-blocking writes. 4.3. Autologout Timer If a server has an inactivity autologout timer, that timer MUST be of at least 30 minutes' duration. The receipt of ANY command from the client during that interval should suffice to reset the autologout timer. Crispin [Page 5] Internet DRAFT IMAP4 June 20, 1994 5. Client Commands 5.1. Client Commands - Any State The following commands are valid in any state: CAPABILITY, NOOP, and LOGOUT. 5.1.1. CAPABILITY Command Arguments: none Data: mandatory untagged response: CAPABILITY Result: OK - capability completed BAD - command unknown or arguments invalid The CAPABILITY command requests a listing of capabilities that the server supports. The server MUST send a single untagged CAPABILITY response with "IMAP4" as the first listed capability before the (tagged) OK response. Example: C: abcd CAPABILITY S: * CAPABILITY IMAP4 S: abcd OK CAPABILITY completed 5.1.2. NOOP Command Arguments: none Data: no specific data for this command (but see below) Result: OK - noop completed BAD - command unknown or arguments invalid The NOOP command always succeeds. It does nothing. Since any command can return a status update as untagged data, the NOOP command can be used as a periodic poll for new messages or message status updates during a period of inactivity. The NOOP command can also be used to reset any inactivity autologout timer on the server. Example: C: a002 NOOP S: a002 OK NOOP completed . . . C: a047 NOOP S: * 22 EXPUNGE Crispin [Page 6] Internet DRAFT IMAP4 June 20, 1994 S: * 23 EXISTS S: * 3 RECENT S: * 14 FETCH (FLAGS (\Seen \Deleted)) S: a047 OK NOOP completed 5.1.3. LOGOUT Command Arguments: none Data: mandatory untagged response: BYE Result: OK - logout completed BAD - command unknown or arguments invalid The LOGOUT command informs the server that the client is done with the session. The server must send a BYE untagged response before the (tagged) OK response, and then close the network connection. Example: C: A023 LOGOUT S: * BYE IMAP4 Server logging out S: A023 OK LOGOUT completed (Server and client then close the connection) 5.2. Client Commands - Non-Authenticated State In non-authenticated state, the AUTHENTICATE or LOGIN command establishes authentication and enter authenticated state. The AUTHENTICATE command provides a general mechanism for a variety of authentication techniques, whereas the LOGIN command uses the traditional user name and plaintext password pair. Server implementations may allow non-authenticated access to certain mailboxes. The convention is to use a LOGIN command with the userid "anonymous". A password is required. It is implementation-dependent what requirements, if any, are placed on the password and what access restrictions are placed on anonymous users. Once authenticated (including as anonymous), it is not possible to re-enter non-authenticated state. In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), the following commands are valid in non-authenticated state: AUTHENTICATE and LOGIN. Crispin [Page 7] Internet DRAFT IMAP4 June 20, 1994 5.2.1. AUTHENTICATE Command Arguments: authentication mechanism name Data: continuation data may be requested Result: OK - authenticate completed, now in authenticated state NO - authenticate failure: unsupported authentication mechanism, credentials rejected BAD - command unknown or arguments invalid, authentication exchange cancelled The AUTHENTICATE command indicates an authentication mechanism to the server. If the server supports the requested authentication mechanism, it performs an authentication protocol exchange to authenticate and identify the user. Optionally, it also negotiates a protection mechanism for subsequent protocol interactions. If the requested authentication mechanism is not supported, the server should reject the AUTHENTICATE command by sending a tagged NO response. The authentication protocol exchange consists of a series of server challenges and client answers that are specific to the authentication mechanism. A server challenge consists of a command continuation request response with the "+" token followed by a BASE64 encoded string. The client answer consists of a line consisting of a BASE64 encoded string. If the client wishes to cancel an authentication exchange, it should issue a line with a single "*". If the server receives such an answer, it must reject the AUTHENTICATE command by sending a tagged BAD response. A protection mechanism provides integrity and privacy protection to the protocol session. If a protection mechanism is negotiated, it is applied to all subsequent data sent over the connection. The protection mechanism takes effect immediately following the CRLF that concludes the authentication exchange for the client, and the CRLF of the tagged OK response for the server. Once the protection mechanism is in effect, the stream of command and response octets is processed into buffers of ciphertext. Each buffer is transferred over the connection as a stream of octets prepended with a four octet field in network byte order that represents the length of the following data. The maximum ciphertext buffer length is defined by the protection mechanism. The server is not required to support any particular authentication mechanism, nor are authentication mechanisms required to support any protection mechanisms. If an AUTHENTICATE command fails with a NO response, the client may try another Crispin [Page 8] Internet DRAFT IMAP4 June 20, 1994 authentication mechanism by issuing another AUTHENTICATE command, or may attempt to authenticate by using the LOGIN command. In other words, the client may request authentication types in decreasing order of preference, with the LOGIN command as a last resort. Example: S: * OK KerberosV4 IMAP4 Server C: A001 AUTHENTICATE KERBEROS_V4 S: + AmFYig== C: BAcAQU5EUkVXLkNNVS5FRFUAOCAsho84kLN3/IJmrMG+25a4DT +nZImJjnTNHJUtxAA+o0KPKfHEcAFs9a3CL5Oebe/ydHJUwYFd WwuQ1MWiy6IesKvjL5rL9WjXUb9MwT9bpObYLGOKi1Qh S: + or//EoAADZI= C: DiAF5A4gA+oOIALuBkAAmw== S: A001 OK Kerberos V4 authentication successful Note: the line breaks in the first client answer are for editorial clarity and are not in real authenticators. 5.2.2. LOGIN Command Arguments: user name password Data: no specific data for this command Result: OK - login completed, now in authenticated state NO - login failure: user name or password rejected BAD - command unknown or arguments invalid The LOGIN command identifies the user to the server and carries the plaintext password authenticating this user. Example: C: a001 LOGIN SMITH SESAME S: a001 OK LOGIN completed 5.3. Client Commands - Authenticated State In authenticated state, commands that manipulate mailboxes as atomic entities are permitted. Of these commands, the SELECT and EXAMINE commands will select a mailbox for access and enter selected state. In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), the following commands are valid in authenticated state: SELECT, EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, Crispin [Page 9] Internet DRAFT IMAP4 June 20, 1994 FIND ALL.MAILBOXES, FIND MAILBOXES, and APPEND. 5.3.1. SELECT Command Arguments: mailbox name Data: mandatory untagged responses: FLAGS, EXISTS, RECENT optional OK untagged responses: UNSEEN, PERMANENTFLAGS Result: OK - select completed, now in selected state NO - select failure, now in authenticated state: no such mailbox, can't access mailbox BAD - command unknown or arguments invalid The SELECT command selects a mailbox so that messages in the mailbox can be accessed. Before returning an OK to the client, the server MUST send the following untagged data to the client: FLAGS Defined flags in the mailbox EXISTS The number of messages in the mailbox RECENT The number of messages added to the mailbox since the previous time this mailbox was read to define the initial state of the mailbox at the client. If it is not possible to determine the messages that were added since the previous time a mailbox was read, then all messages SHOULD be considered recent. The server SHOULD also send an UNSEEN special information token in an OK untagged response, indicating the sequence number of the first unseen message in the mailbox. If the client can not change the permanent state of one or more of the flags listed in the FLAGS untagged response, the server SHOULD send a PERMANENTFLAGS special information token in an OK untagged response, listing the flags that the client may change permanently. Only one mailbox may be selected at a time in a session; simultaneous access to multiple mailboxes requires multiple sessions. The SELECT command automatically deselects any currently selected mailbox before attempting the new selection. Consequently, if a mailbox is selected and a SELECT command that fails is attempted, no mailbox is selected. If the user is permitted to modify the mailbox, the server SHOULD Crispin [Page 10] Internet DRAFT IMAP4 June 20, 1994 prefix the text of the OK response with the "[READ-WRITE]" special information token. If the user is not permitted to modify the mailbox but is permitted read access, the mailbox is selected as read-only, and the server MUST prefix the text of the OK response to SELECT with the "[READ-ONLY]" special information token. Read-only access through SELECT differs from the EXAMINE command in that certain read-only mailboxes may permit the change of permanent state on a per-user (as opposed to global) basis. Netnews messages marked in a user's .newsrc file are an example of such per-user permanent state that can be modified with read-only mailboxes. Example: C: A142 SELECT INBOX S: * 172 EXISTS S: * 1 RECENT S: * OK [UNSEEN 12] Message 12 is first unseen S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited S: A142 OK [READ-WRITE] SELECT completed 5.3.2. EXAMINE Command Arguments: mailbox name Data: mandatory untagged responses: FLAGS, EXISTS, RECENT optional OK untagged responses: UNSEEN, PERMANENTFLAGS Result: OK - examine completed, now in selected state NO - examine failure, now in authenticated state: no such mailbox, can't access mailbox BAD - command unknown or arguments invalid The EXAMINE command is identical to SELECT and returns the same output; however, the selected mailbox is identified as read-only. No changes to the permanent state of the mailbox, including per- user state, are permitted. The text of an OK response to the EXAMINE command MUST begin with the "[READ-ONLY]" special information token. Example: C: A932 EXAMINE blurdybloop S: * 17 EXISTS S: * 2 RECENT S: * OK [UNSEEN 8] Message 8 is first unseen S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) S: * OK [PERMANENTFLAGS ()] No permanent flags permitted Crispin [Page 11] Internet DRAFT IMAP4 June 20, 1994 S: A932 OK [READ-ONLY] EXAMINE completed 5.3.3. CREATE Command Arguments: mailbox name Data: no specific data for this command Result: OK - create completed NO - create failure: can't create mailbox with that name BAD - command unknown or arguments invalid The CREATE command creates a mailbox with the given name. An OK response is returned only if a new mailbox with that name has been created. It is an error to attempt to create INBOX or a mailbox with a name that refers to an extant mailbox. Any error in creation will return a NO response. If the mailbox name is suffixed with the server's hierarchy separator character (as returned from the server by a LIST command), this is a declaration that the client may, in the future, create mailbox names under this name in the hierarchy. Server implementations that do not require this declaration MUST ignore it. Example: C: A003 CREATE owatagusiam/ S: A003 OK CREATE completed C: A004 CREATE owatagusiam/blurdybloop S: A004 OK CREATE completed Note: the interpretation of this example depends on whether "/" was returned as the hierarchy separator from LIST. If "/" is the hierarchy separator, a new level of hierarchy named "owatagusiam" with a member called "blurdybloop" is created. Otherwise, two mailboxes at the same hierarchy level are created. Crispin [Page 12] Internet DRAFT IMAP4 June 20, 1994 5.3.4. DELETE Command Arguments: mailbox name Data: no specific data for this command Result: OK - delete completed NO - delete failure: can't delete mailbox with that name BAD - command unknown or arguments invalid The DELETE command permanently removes the mailbox with the given name. An OK response is returned only if the mailbox has been deleted. It is an error to attempt to delete INBOX or a mailbox name that does not exist. Any error in deletion will return a NO response. Example: C: A683 DELETE blurdybloop S: A683 OK DELETE completed 5.3.5. RENAME Command Arguments: existing mailbox name new mailbox name Data: no specific data for this command Result: OK - rename completed NO - rename failure: can't rename mailbox with that name, can't rename to mailbox with that name BAD - command unknown or arguments invalid The RENAME command changes the name of a mailbox. An OK response is returned only if the mailbox has been renamed. It is an error to attempt to rename from a mailbox name that does not exist or to a mailbox name that already exists. Any error in renaming will return a NO response. Renaming INBOX is permitted; a new, empty INBOX is created in its place. Example: C: Z4S9 RENAME blurdybloop owatagusiam S: Z4S9 OK RENAME completed Crispin [Page 13] Internet DRAFT IMAP4 June 20, 1994 5.3.6. SUBSCRIBE Command Arguments: mailbox Data: no specific data for this command Result: OK - subscribe completed NO - subscribe failure: can't subscribe to that name BAD - command unknown or arguments invalid The SUBSCRIBE command adds the specified mailbox name to the server's list of "active" or "subscribed" mailboxes as returned by the LSUB command. This command returns an OK response only if the subscription is successful. The optional word "MAILBOX" may appear after "SUBSCRIBE". It has no effect on the execution of the command. Example: C: A002 SUBSCRIBE #news.comp.mail.mime S: A002 OK SUBSCRIBE completed 5.3.7. UNSUBSCRIBE Command Arguments: mailbox name Data: no specific data for this command Result: OK - unsubscribe completed NO - unsubscribe failure: can't unsubscribe that name BAD - command unknown or arguments invalid The UNSUBSCRIBE command removes the specified mailbox name from the server's list of "active" or "subscribed" mailboxes as returned by the LSUB command. This command returns an OK response only if the unsubscription is successful. The optional word "MAILBOX" may appear after "UNSUBSCRIBE". It has no effect on the execution of the command. Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime S: A002 OK UNSUBSCRIBE completed Crispin [Page 14] Internet DRAFT IMAP4 June 20, 1994 5.3.8. LIST Command Arguments: reference name mailbox name with possible wildcards Data: untagged responses: LIST Result: OK - list completed NO - list failure: can't list that reference or name BAD - command unknown or arguments invalid The LIST command returns a subset of names from the complete set of all names available to the user. Zero or more untagged LIST replies are returned, containing the name attributes, hierarchy delimiter, and name; see the description of the LIST reply for more detail. An empty ("" string) reference argument indicates that the mailbox name is interpreted as by SELECT. The returned mailbox names MUST match the supplied mailbox name pattern. A non-empty reference argument is the name of a mailbox or a level of mailbox hierarchy, and indicates a context in which the mailbox name is interpreted in an implementation-defined manner. The reference and mailbox name arguments are canonicalized to an interpreted form that represents an unambiguous left-to-right hierarchy. The returned mailbox names will be in the interpreted form. Any part of the reference that is included in the interpreted form SHOULD be in the same form as the reference argument and not canonicalized into some other form. Here are some examples of how references and mailbox names might be interpreted on a UNIX-based server: Reference Mailbox Name Interpretation ------------ ------------ -------------- ~smith/Mail/ foo.* ~smith/Mail/foo.* ~smith/Mail/ /usr/doc/foo /usr/doc/foo archive/ % archive/% archive/ ~fred/Mail/* ~fred/Mail/* #news. comp.mail.* #news.comp.mail.* Note that "~smith/Mail" should not be canonicalized into something like "/u2/users/smith/Mail" because "~smith/Mail" is taken from the reference and thus its form should be preserved. The character "*" is a wildcard, and matches zero or more Crispin [Page 15] Internet DRAFT IMAP4 June 20, 1994 characters at this position. The character "%" is similar to "*", but it does not match a hierarchy delimiter. Server implementations are permitted to "hide" otherwise- accessible mailboxes from the wildcard characters, by preventing certain characters or names from matching a wildcard in certain situations. For example, a UNIX-based server might restrict the interpretation of "*" so that an initial "/" character does not match. The special name INBOX is included in the output from LIST if it matches the input arguments and INBOX is supported by this server for this user. The criteria for omitting INBOX is whether SELECT INBOX will return failure; it is not relevant whether the user's real INBOX resides on this or some other server. Example: C: A002 LIST "~/Mail/" "%" S: * LIST (\Noselect) "/" ~/Mail/foo S: * LIST () "/" ~/Mail/meetings S: A002 OK LIST completed 5.3.9. LSUB Command Arguments: reference name mailbox name with possible wildcards Data: untagged responses: LSUB Result: OK - lsub completed NO - lsub failure: can't list that reference or name BAD - command unknown or arguments invalid The LSUB command returns a subset of names from the set of names that the user has declared as being "active" or "subscribed". Zero or more untagged LSUB replies are returned. The arguments to LSUB are in the same form as those for LIST. Example: C: A002 LSUB "#news." "comp.mail.*" S: * LSUB () "." #news.comp.mail.mime S: * LSUB () "." #news.comp.mail.misc S: A002 OK LSUB completed Crispin [Page 16] Internet DRAFT IMAP4 June 20, 1994 5.3.10. FIND ALL.MAILBOXES Command Arguments: mailbox name with possible wildcards Data: untagged responses: MAILBOX Result: OK - find completed NO - find failure: can't list that name BAD - command unknown or arguments invalid This command is OBSOLETE. It is NOT required to support it in new server implementations. It is documented here for the benefit of implementors who may wish to support it for compatibility with old client implementations. The FIND ALL.MAILBOXES command returns a subset of names from the complete set of all names available to the user. It returns zero or more untagged MAILBOX replies. The mailbox argument to FIND ALL.MAILBOXES is similar to that for LIST with an empty reference, except that the characters "%" and "?" match a single character. Example: C: A002 FIND ALL.MAILBOXES * S: * MAILBOX blurdybloop S: * MAILBOX INBOX S: A002 OK FIND ALL.MAILBOXES completed 5.3.11. FIND MAILBOXES Command Arguments: mailbox name with possible wildcards Data: untagged responses: MAILBOX Result: OK - find completed NO - find failure: can't list that name BAD - command unknown or arguments invalid This command is OBSOLETE. It is NOT required to support it in new server implementations. It is documented here for the benefit of implementors who may wish to support it for compatibility with old client implementations. The FIND MAILBOXES command returns a subset of names from the set of names that the user has declared as being "active" or "subscribed". It returns zero or more untagged MAILBOX replies. The mailbox argument to FIND MAILBOXES is similar to that for LSUB with an empty reference, except that the characters "%" and "?" Crispin [Page 17] Internet DRAFT IMAP4 June 20, 1994 match a single character. Example: C: A002 FIND MAILBOXES * S: * MAILBOX blurdybloop S: * MAILBOX INBOX S: A002 OK FIND MAILBOXES completed 5.3.12. APPEND Command Arguments: mailbox name optional flag list optional date/time string message literal Data: no specific data for this command Result: OK - append completed NO - append error: can't append to that mailbox, error in flags or date/time or message text BAD - command unknown or arguments invalid The APPEND command appends the literal argument as a new message in the specified destination mailbox. This argument is in the format of an RFC 822 message. 8-bit characters are permitted in the message. A server implementation that is unable to preserve 8-bit data properly MUST be able to reversibly convert 8-bit APPEND data to 7-bit using MIME. If a flag list or date_time are specified, that data SHOULD be set in the resulting message; otherwise, the defaults of empty flags and the current date/time are used. If the append is unsuccessful for any reason, the mailbox MUST be restored to its state before the APPEND attempt; no partial appending is permitted. If the mailbox is currently selected, the normal new mail actions should occur. Server implementations SHOULD return a NO response if the length of the literal is zero. If the destination mailbox does not exist, a server MUST return an error, and MUST NOT automatically create the mailbox. Unless it is certain that the destination mailbox can not be created, the server MUST send the special information token "[TRYCREATE]" as the prefix of the text of the tagged NO response. This gives a hint to the client that it can attempt a CREATE command and retry Crispin [Page 18] Internet DRAFT IMAP4 June 20, 1994 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 C: Subject: afternoon meeting C: To: mooch@owatagu.siam.edu C: Message-Id: C: Mime-Version: 1.0 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII C: C: Hello Joe, do you think we can meet at 3:30 tomorrow? C: S: A003 OK APPEND completed Note: the APPEND command is not used for message delivery, because it does not provide a mechanism to transfer SMTP (RFC 821) envelope information. 5.4. Client Commands - Selected State In selected state, commands that manipulate messages in a mailbox are permitted. In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), and the authenticated state commands (SELECT, EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, FIND ALL.MAILBOXES, FIND MAILBOXES, and APPEND), the following commands are valid in the selected state: CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, PARTIAL, STORE, COPY, and UID. 5.4.1. CHECK Command Arguments: none Data: no specific data for this command Result: OK - check completed BAD - command unknown or arguments invalid The CHECK command requests a checkpoint of the currently selected mailbox. A checkpoint refers to any implementation-dependent housekeeping associated with the mailbox (e.g. resolving the server's in-memory state of the mailbox with the state on its disk) that is not normally executed as part of each command. A checkpoint may take a non-instantaneous amount of real time to Crispin [Page 19] Internet DRAFT IMAP4 June 20, 1994 complete. If a server implementation has no such housekeeping considerations, CHECK is equivalent to NOOP. There is no guarantee that an EXISTS untagged response will happen as a result of CHECK. NOOP, not CHECK, should be used for new mail polling. Example: C: FXXZ CHECK S: FXXZ OK CHECK Completed 5.4.2. CLOSE Command Arguments: none Data: no specific data for this command Result: OK - close completed, now in authenticated state NO - close failure: no mailbox selected BAD - command unknown or arguments invalid The CLOSE command permanently removes from the currently selected mailbox all messages that have the \Deleted flag set, and returns to authenticated state from selected state. No untagged EXPUNGE responses are sent. No messages are removed, and no error is given, if the mailbox is selected by an EXAMINE command or is otherwise selected read-only. Even when a mailbox is selected, it is not required to send a CLOSE command before a SELECT, EXAMINE, or LOGOUT command. The SELECT, EXAMINE, and LOGOUT commands implicitly close the currently selected mailbox without doing an expunge. However, when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT sequence is considerably faster than an EXPUNGE-LOGOUT or EXPUNGE-SELECT because no untagged EXPUNGE responses (which the client would probably ignore) are sent. Example: C: A341 CLOSE S: A341 OK CLOSE completed Crispin [Page 20] Internet DRAFT IMAP4 June 20, 1994 5.4.3. EXPUNGE Command Arguments: none Data: untagged responses: EXPUNGE Result: OK - expunge completed NO - expunge failure: can't expunge (e.g. permission denied) BAD - command unknown or arguments invalid The EXPUNGE command permanently removes from the currently selected mailbox all messages that have the \Deleted flag set. Before returning an OK to the client, an untagged EXPUNGE response is sent for each message that is removed. The message number for each successive message in the mailbox is immediately decremented by 1; and this decrement is reflected in subsequent untagged EXPUNGE responses. Example: C: A202 EXPUNGE S: * 3 EXPUNGE S: * 3 EXPUNGE S: * 5 EXPUNGE S: * 8 EXPUNGE S: A202 OK EXPUNGE completed Note: in this example, messages 3, 4, 7, and 11 had the \Deleted flag set. 5.4.4. SEARCH Command Arguments: optional character set specification searching criteria (one or more) Data: mandatory untagged response: SEARCH Result: OK - search completed NO - search error: can't search that character set or criteria BAD - command unknown or arguments invalid The SEARCH command searches the mailbox for messages that match the given searching criteria. Searching criteria consist of one or more search keys. The untagged SEARCH response from the server contains a listing of message numbers corresponding to those messages that match the searching criteria. Crispin [Page 21] Internet DRAFT IMAP4 June 20, 1994 When multiple keys are specified, the result is the intersection (AND function) of all the messages that match those keys. For example, the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers to all deleted messages from Smith that were placed in the mailbox since February 1, 1994. A search key may also be a parenthesized list of one or more search keys (e.g. for use with the OR and NOT keys). Server implementations MAY exclude MIME body parts with terminal content types other than TEXT and MESSAGE from consideration in SEARCH matching. The optional character set specification consists of the word CHARSET followed by a registered MIME character set. It indicates the character set of the strings that appear in the search criteria. RFC 1522 strings that appear in RFC 822/MIME message headers, and MIME content transfer encodings, MUST be decoded before matching. Except for US-ASCII, it is not required that any particular character set be supported. If the server does not support the specified character set, it MUST return a tagged NO response (not a BAD). In all search keys that use strings, a message matches the key if the string is a substring of the field. The matching is case- insensitive. The currently defined search keys are as follows. Refer to the Formal Syntax section for the precise syntactic definitions of the arguments. Messages within the specified sequence range. ALL All messages in the mailbox; the default initial key for ANDing. ANSWERED Messages with the \Answered flag set. BCC Messages that contain the specified string in the envelope structure's BCC field. BEFORE Messages whose internal date is earlier than the specified date. BODY Messages that contain the specified string in the body of the message. CC Messages that contain the specified string in the Crispin [Page 22] Internet DRAFT IMAP4 June 20, 1994 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 Messages that contain the specified string in the envelope structure's FROM field. HEADER Messages that have a header with the specified field-name (as defined in RFC 822) and that contains the specified string in the RFC 822 field-body. KEYWORD Messages with the specified keyword set. LARGER Messages with an RFC822.SIZE larger than the specified number of octets. NEW Messages that have the \Recent flag set but not the \Seen flag. This is functionally equivalent to "(RECENT UNSEEN)". NOT 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 Messages whose internal date is within the specified date. OR Messages that match either search key. RECENT Messages that have the \Recent flag set. SEEN Messages that have the \Seen flag set. SENTBEFORE Messages whose RFC 822 Date: header is earlier than Crispin [Page 23] Internet DRAFT IMAP4 June 20, 1994 the specified date. SENTON Messages whose RFC 822 Date: header is within the specified date. SENTSINCE Messages whose RFC 822 Date: header is within or later than the specified date. SINCE Messages whose internal date is within or later than the specified date. SMALLER Messages with an RFC822.SIZE smaller than the specified number of octets. SUBJECT Messages that contain the specified string in the envelope structure's SUBJECT field. TEXT Messages that contain the specified string in the header or body of the message. TO Messages that contain the specified string in the envelope structure's TO field. UID Messages with unique identifiers within the specified unique identifier sequence range. UNANSWERED Messages that do not have the \Answered flag set. UNDELETED Messages that do not have the \Deleted flag set. UNDRAFT Messages that do not have the \Draft flag set. UNFLAGGED Messages that do not have the \Flagged flag set. UNKEYWORD Messages that do not have the specified keyword set. UNSEEN Messages that do not have the \Seen flag set. Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith" S: * SEARCH 2 84 882 S: A282 OK SEARCH completed Crispin [Page 24] Internet DRAFT IMAP4 June 20, 1994 5.4.5. FETCH Command Arguments: message sequence message data item names Data: untagged responses: FETCH Result: OK - fetch completed NO - fetch error: can't fetch that data BAD - command unknown or arguments invalid The FETCH command retrieves data associated with a message in the mailbox. The data items to be fetched may be either a single atom or a parenthesized list. The currently defined data items that can be fetched are: ALL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE) BODY Non-extensible form of BODYSTRUCTURE. BODY[
] The text of a particular body section. The section specification is a set of one or more part numbers delimited by periods. Single-part messages only have a part 1. Multipart messages are assigned consecutive part numbers, as they occur in the message. If a particular part is of type message or multipart, its parts must be indicated by a period followed by the part number within that nested multipart part. It is not permitted to fetch a multipart part itself, only its individual members. A part of type MESSAGE and subtype RFC822 also has nested parts. These are the parts of the MESSAGE part's body. Nested part 0 of a part of type MESSAGE and subtype RFC822 is the RFC 822 header of the message. Every message has at least one part. Crispin [Page 25] Internet DRAFT IMAP4 June 20, 1994 Here is an example of a complex message with its associated section specifications: 0 (RFC 822 header of the message) MULTIPART/MIXED 1 TEXT/PLAIN 2 APPLICATION/OCTET-STREAM 3 MESSAGE/RFC822 3.0 (RFC 822 header of the message) 3.1 TEXT/PLAIN 3.2 APPLICATION/OCTET-STREAM MULTIPART/MIXED 4.1 IMAGE/GIF 4.2 MESSAGE/RFC822 4.2.0 (RFC 822 header of the message) 4.2.1 TEXT/PLAIN MULTIPART/ALTERNATIVE 4.2.2.1 TEXT/PLAIN 4.2.2.2 TEXT/RICHTEXT Note that there is no section specification for the Multi-part parts (no section 4 or 4.2.2). The \Seen flag is implicitly set; if this causes the flags to change they should be included as part of the fetch responses. BODY.PEEK[
] An alternate form of BODY[section] that does not implicitly set the \Seen flag. BODYSTRUCTURE The MIME body structure of the message. This is computed by the server by parsing the MIME header lines. ENVELOPE The envelope structure of the message. This is computed by the server by parsing the RFC 822 header into the component parts, defaulting various fields as necessary. FAST Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE) Crispin [Page 26] Internet DRAFT IMAP4 June 20, 1994 FLAGS The flags that are set for this message. FULL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE BODY) INTERNALDATE The date and time of final delivery of the message as defined by RFC 821. RFC822 The message in RFC 822 format. The \Seen flag is implicitly set; if this causes the flags to change they should be included as part of the fetch responses. This is the concatenation of RFC822.HEADER and RFC822.TEXT. RFC822.PEEK An alternate form of RFC822 that does not implicitly set the \Seen flag. RFC822.HEADER The RFC 822 format header of the message as stored on the server including the delimiting blank line between the header and the body. RFC822.HEADER.LINES All header lines (including continuation lines) of the RFC 822 format header of the message with a field-name (as defined in RFC 822) that matches any of the strings in header_list. The matching is case-insensitive but otherwise exact. The delimiting blank line between the header and the body is always included. RFC822.HEADER.LINES.NOT All header lines (including continuation lines) of the RFC 822 format header of the message with a field-name (as defined in RFC 822) that does not match any of the strings in header_list. The matching is case-insensitive but otherwise exact. The delimiting blank line between the header and the body is always included. RFC822.SIZE The number of octets in the message, as expressed in RFC 822 format. RFC822.TEXT The text body of the message, omitting the RFC 822 header. The \Seen flag is implicitly set; if this causes the flags to change they should be included Crispin [Page 27] Internet DRAFT IMAP4 June 20, 1994 as part of the fetch responses. RFC822.TEXT.PEEK An alternate form of RFC822.TEXT that does not implicitly set the \Seen flag. UID The unique identifier for the message. Example: C: A654 FETCH 2:4 (FLAGS RFC822.HEADER.LINES (DATE FROM)) S: * 2 FETCH .... S: * 3 FETCH .... S: * 4 FETCH .... S: A003 OK FETCH completed 5.4.6. PARTIAL Command Arguments: message number message data item name position of first octet number of octets Data: untagged responses: FETCH Result: OK - partial completed NO - partial error: can't fetch that data BAD - command unknown or arguments invalid The PARTIAL command is equivalent to the associated FETCH command, with the added functionality that only the specified number of octets, beginning at the specified starting octet, are returned. Only a single message can be fetched at a time. The first octet of a message, and hence the minimum for the starting octet, is octet 1. The following FETCH items are valid data for PARTIAL: RFC822, RFC822.HEADER, RFC822.TEXT, BODY[section], as well as any .PEEK forms of these. Any partial fetch that attempts to read beyond the end of the text is truncated as appropriate. If the starting octet is beyond the end of the text, an empty string is returned. The data are returned with the FETCH response. There is no indication of the range of the partial data in this response. It is not possible to stream multiple PARTIAL commands of the same data item without processing and synchronizing at each step, since Crispin [Page 28] Internet DRAFT IMAP4 June 20, 1994 streamed commands may be executed out of order. There is no requirement that partial fetches follow any sequence. For example, if a partial fetch of octets 1 through 10000 breaks in an awkward place for BASE64 decoding, it is permitted to continue with a partial fetch of 9987 through 19987, etc. The handling of the \Seen flag is the same as in the associated FETCH command. Example: C: A005 PARTIAL 4 RFC822 1 1024 S: * 1 FETCH (RFC822 {1024} S: Return-Path: S: ... S: ......... FLAGS (\Seen)) S: A005 OK PARTIAL completed 5.4.7. STORE Command Arguments: message sequence message data item name value for message data item Data: untagged responses: FETCH Result: OK - store completed NO - store error: can't store that data BAD - command unknown or arguments invalid The STORE command alters data associated with a message in the mailbox. Normally, STORE will return the updated value of the data with an untagged FETCH response. A suffix of ".SILENT" in the data item name prevents the untagged FETCH, and the server should assume that the client has determined the updated value itself or does not care about the updated value. The currently defined data items that can be stored are: FLAGS Replace the flags for the message with the argument. The new value of the flags are returned as if a FETCH of those flags was done. FLAGS.SILENT Equivalent to FLAGS, but without returning a new Crispin [Page 29] Internet DRAFT IMAP4 June 20, 1994 value. +FLAGS Add the argument to the flags for the message. The new value of the flags are returned as if a FETCH of those flags was done. +FLAGS.SILENT Equivalent to +FLAGS, but without returning a new value. -FLAGS Remove the argument from the flags for the message. The new value of the flags are returned as if a FETCH of those flags was done. -FLAGS.SILENT Equivalent to -FLAGS, but without returning a new value. Example: C: A003 STORE 2:4 +FLAGS (\Deleted) S: * 2 FETCH FLAGS (\Deleted \Seen) S: * 3 FETCH FLAGS (\Deleted) S: * 4 FETCH FLAGS (\Deleted \Flagged \Seen) S: A003 OK STORE completed 5.4.8. COPY Command Arguments: message sequence mailbox name Data: no specific data for this command Result: OK - copy completed NO - copy error: can't copy those messages or to that name BAD - command unknown or arguments invalid The COPY command copies the specified message(s) to the specified destination mailbox. The flags and internal date of the message(s) SHOULD be preserved in the copy. If the destination mailbox does not exist, a server SHOULD return an error. It SHOULD NOT automatically create the mailbox. Unless it is certain that the destination mailbox can not be created, the server MUST send the special information token "[TRYCREATE]" as Crispin [Page 30] Internet DRAFT IMAP4 June 20, 1994 the prefix of the text of the tagged NO response. This gives a hint to the client that it can attempt a CREATE command and retry the COPY if the CREATE is successful. If the COPY command is unsuccessful for any reason, server implementations MUST restore the destination mailbox to its state before the COPY attempt. Example: C: A003 COPY 2:4 MEETING S: A003 OK COPY completed 5.4.9. UID Command Arguments: command name command arguments Data: untagged responses: FETCH, SEARCH Result: OK - UID command completed NO - UID command error BAD - command unknown or arguments invalid The UID command takes as its arguments a COPY, FETCH, SEARCH, or STORE command with arguments appropriate for the associated command. However, instead of message numbers, it uses unique identifiers in the sequence argument to reference a particular message or range of messages. The unique identifier of a message is guaranteed not to refer to any other message in the mailbox. Unlike sequence numbers, unique identifiers persist across sessions. This permits a client to resynchronize its state from a previous session with the server (e.g. disconnected or offline access clients). Sequence ranges are permitted; however, there is no guarantee that unique identifiers be contiguous. A non-existent unique identifier within a sequence range is ignored without any error message generated. The number after the "*" in an untagged FETCH response is always a message number, not a unique identifier, even for a UID command response. However, server implementations MUST implicitly include the UID message data item as part of any FETCH response caused by a UID command, regardless of whether UID was specified as a message data item to the FETCH. The numbers returned in a SEARCH response for a UID SEARCH command Crispin [Page 31] Internet DRAFT IMAP4 June 20, 1994 are unique identifiers. Example: C: A003 UID FETCH 4827313:4828442 FLAGS S: * 23 FETCH (FLAGS (\Seen) UID 4827313) S: * 24 FETCH (FLAGS (\Seen) UID 4827943) S: * 25 FETCH (FLAGS (\Seen) UID 4828442) S: A999 UID FETCH completed 5.5. Client Commands - Experimental/Expansion 5.5.1. X Command Arguments: implementation defined Data: implementation defined Result: OK - command completed NO - failure BAD - command unknown or arguments invalid Any command prefixed with an X is an experimental command. Commands which are not part of this specification, or a standard or standards-track revision of this specification, MUST use the X prefix. Any added untagged responses issued by an experimental command MUST also be prefixed with an X. Server implementations MUST NOT send any such untagged responses, unless the client requested it by issuing the associated experimental command. Example: C: A442 XPIG-LATIN S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay S: A442 OK XPIG-LATIN ompleted-cay Crispin [Page 32] Internet DRAFT IMAP4 June 20, 1994 6. Server Responses Server responses are in three forms: status responses, server data, and command continuation request. An untagged response is indicated by the token "*" instead of a tag. For historical reasons, untagged responses are also called "unsolicited data", although strictly speaking only unilateral server data is truly "unsolicited". Status responses that are tagged indicate the completion result of a client command, and have a tag matching the command. Untagged status responses indicate server greeting, or server status that does not indicate the completion of a command. Server data are untagged. These are sent as a result of certain client operations, or unilaterally. There is no syntactic difference between server data that resulted from a specific command and server data that were sent unilaterally. An example of unilateral untagged responses occurs when the IMAP connection is in selected state. In selected state, the server checks the mailbox for new messages as part of the execution of each command. If new messages are found, the server sends untagged EXISTS and RECENT responses reflecting the new size of the mailbox. Server implementations that offer multiple simultaneous access to the same mailbox should also send appropriate unilateral untagged FETCH and EXPUNGE responses if another agent changes the state of any message flags or expunges any messages. Command continuation request responses use the token "+" instead of a tag. These responses are sent by the server to indicate acceptance of an incomplete client command and readiness for the remainder of the command. 6.1. Server Responses - Status Responses Status responses may contain an optional special information token. A special information token consists of data inside square brackets, and and contains additional information or status codes for client software. The currently defined special information tokens are: ALERT The human-readable text contains a special alert that MUST be presented to the user in a fashion Crispin [Page 33] Internet DRAFT IMAP4 June 20, 1994 that calls the user's attention to the message. PARSE The human-readable text represents an error in parsing the RFC 822 or MIME headers of a message in the mailbox. PERMANENTFLAGS Followed by a list of flags, indicates which of the known flags that the client may change permanently. Any flags that are in the FLAGS untagged response, but not the PERMANENTFLAGS list, can not be set permanently. If the client attempts to STORE a flag that is not in the PERMANENTFLAGS list, the server will either reject it with a NO reply or store the state for the remainder of the current session only. The PERMANENTFLAGS list may also include the special flag \*, which indicates that it is possible to create new keywords by attempting to store those flags in the mailbox. READ-ONLY The mailbox is selected read-only, or its access while selected has changed from read-write to read-only. READ-WRITE The mailbox is selected read-write, or its access while selected has changed from read-only to read- write. TRYCREATE An APPEND or COPY attempt is failing because the target mailbox does not exist (as opposed to some other reason). This is a hint to the client that the operation may succeed if the mailbox is first created by the CREATE command. UNSEEN Followed by a decimal number, indicates the number of the first message without the \Seen flag set. Other special information tokens defined by particular client or server implementations should be prefixed with an "X" until they are added to a revision of this protocol. 6.1.1. OK Response Data: optional special information token human-readable text The OK response indicates an information message from the server. When tagged, it indicates successful completion of the associated Crispin [Page 34] Internet DRAFT IMAP4 June 20, 1994 command. The human-readable text may be presented to the user as an information message. The untagged form indicates an information-only message; the nature of the information may be indicated by a special information token. The untagged form is also used as one of three possible greetings at session startup. It indicates that the session is not yet authenticated and that a LOGIN command is needed. Example: S: * OK IMAP4 server ready C: A001 LOGIN fred blurdybloop S: * OK [ALERT] System shutdown in 10 minutes S: A001 OK LOGIN Completed 6.1.2. NO Response Data: optional special information token human-readable text The NO response indicates an operational error message from the server. When tagged, it indicates unsuccessful completion of the associated command. The untagged form indicates a warning; the command may still complete successfully. The human-readable text describes the condition. Example: C: A222 COPY 1:2 owatagusiam S: * NO Disk is 98% full, please delete unnecessary data S: A222 OK COPY completed C: A222 COPY 3:200 blurdybloop S: * NO Disk is 98% full, please delete unnecessary data S: * NO Disk is 99% full, please delete unnecessary data S: A222 NO COPY failed: disk is full 6.1.3. BAD Response Data: optional special information token human-readable text The BAD response indicates an error message from the server. When tagged, it reports a protocol-level error in the client's command; the tag indicates the command that caused the error. The untagged form indicates a protocol-level error for which the associated command can not be determined; it may also indicate an internal server failure. The human-readable text describes the condition. Example: C: ...very long command line... Crispin [Page 35] Internet DRAFT IMAP4 June 20, 1994 S: * BAD Command line too long C: ...empty line... S: * BAD Empty command line C: A443 EXPUNGE S: * BAD Disk crash, attempting salvage to a new disk! S: * OK Salvage successful, no data lost S: A443 OK Expunge completed 6.1.4. PREAUTH Response Data: optional special information token human-readable text The PREAUTH response is always untagged, and is one of three possible greetings at session startup. It indicates that the session has already been authenticated by external means and thus no LOGIN command is needed. Example: S: * PREAUTH IMAP4 server ready and logged in as Smith 6.1.5. BYE Response Data: optional special information token human-readable text The BYE response is always untagged, and indicates that the server is about to close the connection. The human-readable text may be displayed to the user in a status report by the client. The BYE response may be sent as part of a normal logout sequence, or as a panic shutdown announcement by the server. It is also used by some server implementations as an announcement of an inactivity autologout. This response is also used as one of three possible greetings at session startup. It indicates that the server is not willing to accept a session from this client. Example: S: * BYE Autologout; idle for too long 6.2. Server Responses - Server and Mailbox Status These responses are always untagged. This is how server data are transmitted from the server to the client, often as a result of a command with the same name. Crispin [Page 36] Internet DRAFT IMAP4 June 20, 1994 6.2.1. CAPABILITY Response Data: capability listing The CAPABILITY response occurs as a result of a CAPABILITY command. The capability listing contains a space-separated listing of capability names that the server supports. The first name in the capability listing MUST be the atom "IMAP4". Capability names MUST either begin with "X" or be standard or standards-track IMAP4 extensions registered with IANA. A server MUST NOT offer capability names that are not described in a registered and standardized extension, unless that capability name is prefixed with an "X". Client implementations SHOULD NOT require any capability name other than "IMAP4", and MUST ignore any unknown capability names. A capability name other than IMAP4 indicates that the server supports an extension to the IMAP4 protocol. Server responses MUST conform to this document until the client issues a command that uses the associated extension to the IMAP4 protocol. Example: S: * CAPABILITY IMAP4 XPIG-LATIN 6.2.2. LIST Response Data: name attributes hierarchy delimiter name The LIST response occurs as a result of a LIST command. It returns a single name that matches the LIST specification. There may be multiple LIST responses for a single LIST command. Four name attributes are defined: \Noinferiors It is not possible for any child levels of hierarchy to exist under this name; no child levels exist now and none can be created in the future. \Noselect It is not possible to use this name as a selectable mailbox. \Marked The mailbox has been marked "interesting" by the server; the mailbox probably contains messages that have been added since the last time the mailbox was Crispin [Page 37] Internet DRAFT IMAP4 June 20, 1994 selected. \Unmarked The mailbox does not contain any additional messages since the last time the mailbox was selected. If it is not feasible for the server to determine whether the mailbox is "interesting" or not, it should not send either \Marked or \Unmarked. The hierarchy delimiter is a character used to delimit levels of hierarchy in a mailbox name. A client may use it to create child mailboxes, and to search higher or lower levels of naming hierarchy. All children of a top-level hierarchy node must use the same separator character. A NIL hierarchy delimiter means that no hierarchy exists; the name is a "flat" name. The name represents an unambiguous left-to-right hierarchy, and MUST be valid for use as a reference in LIST and LSUB commands. Unless \Noselect is indicated, the name must also be valid as an argument for commands, such as SELECT, that accept mailbox names. Example: S: * LIST (\Noselect) "/" ~/Mail/foo 6.2.3. LSUB Response Data: name attributes hierarchy delimiter name The LSUB response occurs as a result of an LSUB command. It returns a single name that matches the LSUB specification. There may be multiple LSUB responses for a single LSUB command. The data is identical in format to the LIST response. Example: S: * LSUB () "." #news.comp.mail.misc 6.2.4. MAILBOX Response Data: name The MAILBOX response is OBSOLETE. It MUST NOT be transmitted except in response to the FIND MAILBOXES and FIND ALL.MAILBOXES commands. Client implementations that do not use these commands are NOT required to support this response. It is documented here for the benefit of implementors who may wish to support it for Crispin [Page 38] Internet DRAFT IMAP4 June 20, 1994 compatibility with old client implementations. This response occurs as a result of the FIND MAILBOXES and FIND ALL.MAILBOXES commands. It returns a single name that matches the FIND specification. There are no attributes or hierarchy delimiter. Example: S: * MAILBOX blurdybloop 6.2.5. SEARCH Response Data: zero or more numbers The SEARCH response occurs as a result of a SEARCH or UID SEARCH command. The number(s) refer to those messages that match the search criteria. For SEARCH, these are message sequence numbers; for UID SEARCH, these are unique identifiers. Each number is delimited by a space. Example: S: * SEARCH 2 3 6 6.2.6. FLAGS Response Data: flag list The FLAGS response occurs as a result of a SELECT or EXAMINE command. The flag list is a parenthesized list of flags (at a minimum, the system-defined flags) that are applicable for this mailbox. Flags other than the system flags may also exist, depending on server implementation. Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 6.3. Server Responses - Message Status These responses are always untagged. This is how message data are transmitted from the server to the client, often as a result of a command with the same name. Immediately following the "*" token is a number that represents either a message sequence number or a message count. Crispin [Page 39] Internet DRAFT IMAP4 June 20, 1994 6.3.1. EXISTS Response Data: none The EXISTS response reports the number of messages in the mailbox. This response occurs as a result of a SELECT or EXAMINE command, and if the size of the mailbox changes (e.g. new mail). Example: S: * 23 EXISTS 6.3.2. RECENT Response Data: none The RECENT response reports the number of messages that have arrived since the previous time a SELECT command was done on this mailbox. This response occurs as a result of a SELECT or EXAMINE command, and if the size of the mailbox changes (e.g. new mail). Example: S: * 5 RECENT 6.3.3. EXPUNGE Response Data: none The EXPUNGE response reports that the specified message number has been permanently removed from the mailbox. The message number for each successive message in the mailbox is immediately decremented by 1. For example, if the last 5 messages in a 9-message mailbox are expunged the client will receive 5 untagged EXPUNGE responses for message 5. An EXPUNGE response MUST NOT be sent when no command is in progress; nor while responding to a FETCH, STORE, or SEARCH command. Example: S: * 44 EXPUNGE 6.3.4. FETCH Response Data: message data The FETCH response returns data about a message to the client. The data are pairs of data item names and their values in parentheses. This response occurs as the result of a FETCH or Crispin [Page 40] Internet DRAFT IMAP4 June 20, 1994 STORE command, as well as by unilateral server decision (e.g. flag updates). The current data items are: BODY A form of BODYSTRUCTURE without extension data. BODY[section] A string expressing the body contents of the specified section. The string should be interpreted by the client according to the content transfer encoding, body type, and subtype. 8-bit textual data is permitted if a character set identifier is part of the body parameter list for this section. Non-textual data such as binary data must be transfer encoded into a textual form such as BASE64 prior to being sent to the client. To derive the original binary data, the client must decode the transfer encoded string. BODYSTRUCTURE A parenthesized list that describes the body structure of a message. This is computed by the server by parsing the RFC 822 header and body into the component parts, defaulting various fields as necessary. Multiple parts are indicated by parenthesis nesting. Instead of a body type as the first element of the list there is a nested body. The second element of the list is the multipart subtype (mixed, digest, parallel, alternative, etc.). Extension data follows the multipart subtype. Extension data is never returned with the BODY fetch, but may be returned with a BODYSTRUCTURE fetch. Extension data, if present, must be in the defined order. The extension data of a multipart body part are in the following order: body parameter list A parenthesized list of attribute/value pairs [e.g. (foo bar baz rag) where "bar" is the value of "foo" and "rag" is the value of "baz"] as defined in MIME. Crispin [Page 41] Internet DRAFT IMAP4 June 20, 1994 Any following extension data are not yet defined in this version of the protocol. Such extension data may consist of zero or more NILs, strings, numbers, or potentially nested lists of such data. Client implementations that do a BODYSTRUCTURE fetch MUST be prepared to accept such extension data. Server implementations MUST NOT send such extension data until it has been defined by a revision of this protocol. The basic fields of a non-multipart body part are in the following order: body type A string giving the content type name as defined in MIME body subtype A string giving the content subtype name as defined in MIME body parameter list A parenthesized list of attribute/value pairs [e.g. (foo bar baz rag) where "bar" is the value of "foo" and "rag" is the value of "baz"] as defined in MIME. body id A string giving the content id as defined in MIME. body description A string giving the content description as defined in MIME. body encoding A string giving the content transfer encoding as defined in MIME. body size A number giving the size of the body in octets. Note that this size is the size in its transfer encoding and not the resulting size after any decoding. A body type of type MESSAGE and subtype RFC822 contains, immediately after the basic fields, the envelope structure, body structure, and size in Crispin [Page 42] Internet DRAFT IMAP4 June 20, 1994 text lines of the encapsulated message. A body type of type TEXT contains, immediately after the basic fields, the size of the body in text lines. Note that this size is the size in its transfer encoding and not the resulting size after any decoding. Extension data follows the basic fields and the type-specific fields listed above. Extension data is never returned with the BODY fetch, but may be returned with a BODYSTRUCTURE fetch. Extension data, if present, must be in the defined order. The extension data of a non-multipart body part are in the following order: body MD5 A string giving the content MD5 value as defined in MIME Any following extension data are not yet defined in this version of the protocol, and would be as described above under multipart extension data. ENVELOPE A parenthesized list that describes the envelope structure of a message. This is computed by the server by parsing the RFC 822 header into the component parts, defaulting various fields as necessary. The fields of the envelope structure are in the following order: date, subject, from, sender, reply-to, to, cc, bcc, in-reply-to, and message-id. The date, subject, in-reply-to, and message-id fields are strings. The from, sender, reply-to, to, cc, and bcc fields are parenthesized lists of address structures. An address structure is a parenthesized list that describes an electronic mail address. The fields of an address structure are in the following order: personal name, SMTP (RFC 821) at-domain-list (source route), mailbox name, and host name. RFC 822 group syntax is indicated by a special form of address structure in which the host name field is NIL. If the mailbox name field is also NIL, Crispin [Page 43] Internet DRAFT IMAP4 June 20, 1994 this is an end of group marker (semi-colon in RFC 822 syntax). If the mailbox name field is non-NIL, this is a start of group marker, and the mailbox name field holds the group name phrase. Any field of an envelope or address structure that is not applicable is presented as NIL. Note that the server must default the reply-to and sender fields from the from field; a client is not expected to know to do this. FLAGS A parenthesized list of flags that are set for this message. This may include keywords as well as the following system flags: \Seen Message has been read \Answered Message has been answered \Flagged Message is "flagged" for urgent/special attention \Deleted Message is "deleted" for removal by later EXPUNGE \Draft Message has not completed composition (marked as a draft). as well as the following special flag, which may be fetched but not stored: \Recent Message has arrived since the previous time this mailbox was selected. INTERNALDATE A string containing the date and time of final delivery of the message as defined by SMTP (RFC 821). RFC822 A string expressing the message in RFC 822 format. The header portion of the message must be 7-bit. 8-bit characters are permitted only in the non- header portion of the message only if there are MIME data in the message that identify the character set of the message. RFC822.HEADER A string expressing the RFC 822 format header of the message, including the delimiting blank line between the header and the body. The entire string Crispin [Page 44] Internet DRAFT IMAP4 June 20, 1994 must be 7-bit; 8-bit characters are not permitted in headers. RFC822.HEADER is used to return data for the RFC822.HEADER, RFC822.HEADER.LINES, and RFC822.HEADER.LINES.NOT FETCH data items. Note that a blank line is always included regardless of header line restrictions. RFC822.SIZE A number expressing the number of octets in the message in RFC 822 format. RFC822.TEXT A string expressing the text body of the message, omitting the RFC 822 header. 8-bit characters are permitted only if there are MIME data in the message that identify the character set of the message. UID A number expressing the unique identifier of the message. Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827) 6.3.5. COPY Response Data: none The COPY response is OBSOLETE. It MUST NOT be transmitted by new server implementations. Client implementations MUST ignore this response. It is documented here for the benefit of client implementors who may encounter this response from old server implementations. In some experimental versions of this protocol, this response was returned in response to a COPY command to indicate on a per- message basis that the message was copied successfully. Example: S: * 44 COPY 6.3.6. STORE Response Data: message data The STORE response is OBSOLETE. It MUST NOT be transmitted by new server implementations. Client implementations MUST treat this response as equivalent to the FETCH response. It is documented here for the benefit of client implementors who may encounter this Crispin [Page 45] Internet DRAFT IMAP4 June 20, 1994 response from old server implementations. In some experimental versions of this protocol, this response was returned instead of FETCH in response to a STORE command to report the new value of the flags. Example: S: * 69 STORE (FLAGS (\Deleted)) 6.4. Server Responses - Command Continuation Request The command completion request response is indicated by a "+" token instead of a tag. This form of response indicates that the server is ready to accept the continuation of a command from the client. The remainder of this response is a line of text. This response is used in the AUTHORIZATION command to transmit server data to the client, and request additional client data. This response is also used if an argument to any command is a literal. The client is not permitted to send the text of the literal unless the server indicates that it expects it. This permits the server to process commands and reject errors on a line-by-line basis. Example: C: A001 LOGIN SMITH {7} S: + Ready for additional command text C: fat man S: A001 OK LOGIN completed C: A044 BLURDYBLOOP {102856} S: A044 BAD No such command as "BLURDYBLOOP" Crispin [Page 46] Internet DRAFT IMAP4 June 20, 1994 7. Sample IMAP4 session The following is a transcript of an IMAP4 session. A long line in this sample is broken for editorial clarity. S: * OK IMAP4 Service Ready C: a001 login mrc secret S: a001 OK LOGIN completed C: a002 select inbox S: * 18 EXISTS S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) S: * 2 RECENT S: * OK [UNSEEN 17] Message 17 is the first unseen message S: a002 OK [READ-WRITE] SELECT completed C: a003 fetch 12 full S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "14-Jul-1993 02:44:25 -0700" RFC822.SIZE 4282 ENVELOPE ("Wed, 14 Jul 1993 02:23:25 -0700 (PDT)" "IMAP4 WG mtg summary and minutes" (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) (("Terry Gray" NIL "gray" "cac.washington.edu")) ((NIL NIL "imap" "cac.washington.edu")) ((NIL NIL "minutes" "CNRI.Reston.VA.US") ("John Klensin" NIL "KLENSIN" "INFOODS.MIT.EDU")) NIL NIL "") BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 92)) S: a003 OK FETCH completed C: a004 fetch 12 rfc822.header S: * 12 FETCH (RFC822.HEADER {346} S: Date: Wed, 14 Jul 1993 02:23:25 -0700 (PDT) S: From: Terry Gray S: Subject: IMAP4 WG mtg summary and minutes S: To: imap@cac.washington.edu S: cc: minutes@CNRI.Reston.VA.US, John Klensin S: Message-Id: S: Mime-Version: 1.0 S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII S: S: ) S: a004 OK FETCH completed C: a005 store 12 +flags \deleted S: * 12 FETCH (FLAGS (\Seen \Deleted)) S: a005 OK +FLAGS completed C: a006 logout S: * BYE IMAP4 server terminating connection S: a006 OK LOGOUT completed Crispin [Page 47] Internet DRAFT IMAP4 June 20, 1994 8. Formal Syntax The following syntax specification uses the augmented Backus-Naur Form (BNF) notation as specified in RFC 822 with one exception; the delimiter used with the "#" construct is a single space (SPACE) and not a comma. Except as noted otherwise, all alphabetic characters are case- insensitive. The use of upper or lower case characters to define token strings is for editorial clarity only. Implementations MUST accept these strings in a case-insensitive fashion. Syntax marked as obsolete may be encountered with implementations written for an earlier version of this protocol (e.g. IMAP2). New implementations SHOULD accept obsolete syntax as input, but MUST NOT otherwise use such syntax. address ::= "(" addr_name SPACE addr_adl SPACE addr_mailbox SPACE addr_host ")" addr_adl ::= nstring addr_host ::= nstring ;; NIL indicates RFC 822 group syntax addr_mailbox ::= nstring ;; NIL indicates end of RFC 822 group; if non-NIL ;; and addr_host is NIL, holds RFC 822 group name addr_name ::= nstring alpha ::= "A" / "B" / "C" / "D" / "E" / "F" / "G" / "H" / "I" / "J" / "L" / "M" / "N" / "O" / "P" / "Q" / "R" / "S" / "T" / "U" / "V" / "W" / "X" / "Y" / "Z" / "a" / "b" / "c" / "d" / "e" / "f" / "g" / "h" / "i" / "j" / "l" / "m" / "n" / "o" / "p" / "q" / "r" / "s" / "t" / "u" / "v" / "w" / "x" / "y" / "z" / ;; Case-sensitive append ::= "APPEND" SPACE mailbox [SPACE flag_list] [SPACE date_time] SPACE literal astring ::= atom / string atom ::= 1*ATOM_CHAR ATOM_CHAR ::= Crispin [Page 48] Internet DRAFT IMAP4 June 20, 1994 atom_specials ::= "(" / ")" / "{" / SPACE / CTLs / list_wildcards / quoted_specials authenticate ::= "AUTHENTICATE" SPACE auth_type *(CRLF base64) auth_type ::= atom base64 ::= *(4base64_CHAR) [base64_terminal] base64_char ::= alpha / digit / "+" / "/" base64_terminal ::= (2base64_char "==") / (3base64_char "=") body ::= "(" body_type_1part / body_type_mpart ")" body_extension ::= nstring / number / "(" 1#body_extension ")" ;; Future expansion. Client implementations ;; MUST accept body_extension fields. Server ;; implementations MUST NOT generate ;; body_extension fields except as defined by ;; future standard or standards-track ;; revisions of this specification. body_ext_1part ::= body_fld_md5 [SPACE 1#body_extension] ;; MUST NOT be returned on non-extensible "BODY" fetch body_ext_mpart ::= body_fld_param [SPACE 1#body_extension]] ;; MUST NOT be returned on non-extensible "BODY" fetch body_fields ::= body_fld_param SPACE body_fld_id SPACE body_fld_desc SPACE body_fld_enc SPACE body_fld_octets body_fld_desc ::= nstring body_fld_enc ::= (<"> ("7BIT" / "8BIT" / "BINARY" / "BASE64"/ "QUOTED-PRINTABLE") <">) / string body_fld_id ::= nstring body_fld_lines ::= number body_fld_md5 ::= nstring body_fld_octets ::= number body_fld_param ::= "(" 1#(string string) ")" / nil body_fld_subtyp ::= string Crispin [Page 49] Internet DRAFT IMAP4 June 20, 1994 body_type_1part ::= (body_type_basic / body_type_msg / body_type_text) [SPACE body_ext_1part] body_type_basic ::= (<"> ("APPLICATION" / "AUDIO" / "IMAGE" / "MESSAGE" / "VIDEO") <">) / string) SPACE body_fld_subtyp SPACE body_fields ;; MESSAGE subtype MUST NOT be "RFC822" body_type_mpart ::= 1*body SPACE body_fld_subtyp [SPACE body_ext_mpart] body_type_msg ::= <"> "MESSAGE" <"> SPACE <"> "RFC822" <"> SPACE body_fields SPACE envelope SPACE body SPACE body_fld_lines body_type_text ::= <"> "TEXT" <"> SPACE body_fld_subtyp SPACE body_fields SPACE body_fld_lines capability ::= atom ;; Must begin with "X" or be registered with IANA ;; as standard or standards-track CHAR ::= CHAR8 ::= command ::= tag SPACE (command_any / command_auth / command_nonauth / command_select) CRLF ;; Modal based on state command_any ::= "CAPABILITY" / "LOGOUT" / "NOOP" / x_command ;; Valid in all states command_auth ::= append / create / delete / examine / find / list / lsub / rename / select / subscribe / unsubscribe / ;; Valid only when in Authenticated or Selected state command_nonauth ::= login / authenticate ;; Valid only when in Non-Authenticated state command_select ::= "CHECK" / "CLOSE" / "EXPUNGE" / copy / fetch / partial / store / uid / search ;; Valid only when in Selected state continue_req ::= "+" SPACE (resp_text / base64) copy ::= "COPY" SPACE sequence SPACE mailbox CR ::= Crispin [Page 50] Internet DRAFT IMAP4 June 20, 1994 create ::= "CREATE" SPACE mailbox ;; Use of INBOX gives a NO error CRLF ::= CR LF CTL ::= date ::= date_text / <"> date_text <"> date_day ::= 1*2digit ;; Day of month date_day_fixed ::= (SPACE digit) / 2digit ;; Fixed-format version of date_day date_month ::= "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" / "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec" date_text ::= date_day "-" date_month "-" (date_year / date_year_old) date_year ::= 4digit date_year_old ::= 2digit ;; OBSOLETE, (year - 1900) date_time ::= <"> (date_time_new / date_time_old) <"> date_time_new ::= date_day_fixed "-" date_month "-" date_year SPACE time SPACE zone date_time_old ::= date_day_fixed "-" date_month "-" date_year_old SPACE time "-" zone_old ;; OBSOLETE delete ::= "DELETE" SPACE mailbox ;; Use of INBOX gives a NO error digit ::= "0" / "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9" envelope ::= "(" env_date SPACE env_subject SPACE env_from SPACE env_sender SPACE env_reply-to SPACE env_to SPACE env_cc SPACE env_bcc SPACE env_in-reply-to SPACE env_message-id ")" env_bcc ::= "(" 1*address ")" / nil env_cc ::= "(" 1*address ")" / nil Crispin [Page 51] Internet DRAFT IMAP4 June 20, 1994 env_date ::= nstring env_from ::= "(" 1*address ")" / nil env_in-reply-to ::= nstring env_message-id ::= nstring env_reply-to ::= "(" 1*address ")" / nil env_sender ::= "(" 1*address ")" / nil env_subject ::= nstring env_to ::= "(" 1*address ")" / nil examine ::= "EXAMINE" SPACE mailbox fetch ::= "FETCH" SPACE sequence SPACE ("ALL" / "FULL" / "FAST" / fetch_att / "(" 1#fetch_att ")") fetch_att ::= "BODY" / "BODYSTRUCTURE" / "BODY" [".PEEK"] "[" section "]" / "ENVELOPE" / "FLAGS" / "INTERNALDATE" / "UID" / "RFC822" (([".TEXT"] [".PEEK"]) / ".SIZE" / (".HEADER" [".LINES" [".NOT"] SPACE header_list]) find ::= "FIND" SPACE ["ALL."] "MAILBOXES" SPACE list_mailbox ;; OBSOLETE flag ::= "\Answered" / "\Flagged" / "\Deleted" / "\Seen" / "\Draft" / flag_keyword / flag_extension flag_extension ::= "\" atom ;; Future expansion. Client implementations ;; MUST accept flag_extension flags. Server ;; implementations MUST NOT generate ;; flag_extension flags except as defined by ;; future standard or standards-track ;; revisions of this specification. flag_keyword ::= atom flag_list ::= "(" #flag ")" greeting ::= "*" SPACE (resp_cond_auth / resp_cond_bye) CRLF header_line ::= astring Crispin [Page 52] Internet DRAFT IMAP4 June 20, 1994 header_list ::= "(" 1#header_line ")" LF ::= list ::= "LIST" SPACE mailbox SPACE list_mailbox list_mailbox ::= 1*(ATOM_CHAR / list_wildcards) / string list_wildcards ::= "%" / "*" literal ::= "{" number "}" CRLF 1*CHAR8 ;; The number represents the number of CHAR8 octets login ::= "LOGIN" SPACE userid SPACE password lsub ::= "LSUB" SPACE mailbox SPACE list_mailbox mailbox ::= "INBOX" / astring ;; INBOX is case-insensitive. Other names may be ;; case-sensitive depending on implementation. mailbox_data ::= "FLAGS" SPACE flag_list / "LIST" SPACE mailbox_list / "LSUB" SPACE mailbox_list / "MAILBOX" SPACE text / "SEARCH" [SPACE 1#number] mailbox_list ::= "(" #("\Marked" / "\Noinferiors" / "\Noselect" / "\Unmarked" / flag_extension) ")" SPACE (<"> QUOTED_CHAR <"> / nil) SPACE mailbox message_data ::= number SPACE ("EXISTS" / "RECENT" / "EXPUNGE" / ("FETCH" SPACE msg_fetch) / msg_obsolete) msg_fetch ::= "(" 1#("BODY" SPACE body / "BODYSTRUCTURE" SPACE body / "BODY[" section "]" SPACE nstring / "ENVELOPE" SPACE envelope / "FLAGS" SPACE "(" #(flag / "\Recent") ")" / "INTERNALDATE" SPACE date_time / "RFC822" [".HEADER" / ".TEXT"] SPACE nstring / "RFC822.SIZE" SPACE number / "UID" SPACE uniqueid) ")" msg_obsolete ::= "COPY" / ("STORE" SPACE msg_fetch) ;; OBSOLETE untagged data responses nil ::= "NIL" nstring ::= string / nil number ::= 1*digit Crispin [Page 53] Internet DRAFT IMAP4 June 20, 1994 partial ::= "PARTIAL" SPACE number SPACE fetch_att_text SPACE number SPACE number password ::= astring quoted ::= <"> *QUOTED_CHAR <"> QUOTED_CHAR ::= / "\" quoted_specials quoted_specials ::= <"> / "\" rename ::= "RENAME" SPACE mailbox SPACE mailbox ;; Use of INBOX as a destination gives a NO error response ::= *response_data response_done response_data ::= "*" SPACE (resp_cond_state / resp_cond_bye / mailbox_data / message_data / server_data) CRLF response_done ::= response_tagged / response_fatal response_fatal ::= "*" SPACE resp_cond_bye CRLF response_tagged ::= tag SPACE resp_cond_state CRLF resp_cond_auth ::= ("OK" / "PREAUTH") SPACE resp_text ;; Authentication condition resp_cond_bye ::= "BYE" SPACE resp_text ;; Server will disconnect condition resp_cond_state ::= ("OK" / "NO" / "BAD") SPACE resp_text ;; Status condition resp_text ::= [resp_token SPACE] (text_1522 / text) resp_token ::= "[ALERT]" / "[PARSE]" / "[PERMANENTFLAGS" SPACE "(" #(flag / "\*") ")" "]" / "[READ-ONLY]" / "[READ-WRITE]" / "[TRYCREATE]" / "[UNSEEN" SPACE number "]" / "[" atom [SPACE 1*] "]" search ::= "SEARCH" SPACE ["CHARSET" SPACE astring SPACE] search_criteria ;; Character set must be registered with IANA ;; as a MIME character set Crispin [Page 54] Internet DRAFT IMAP4 June 20, 1994 search_criteria ::= 1#search_key search_key ::= search_new / search_old search_new ::= "DRAFT" / "HEADER" SPACE header_line SPACE astring / "LARGER" SPACE number / "NOT" SPACE search_key / "OR" SPACE search_key SPACE search_key / "SENTBEFORE" SPACE date / "SENTON" SPACE date / "SENTSINCE" SPACE date / "SMALLER" SPACE number / "UID" SPACE sequence / "UNDRAFT" / sequence / "(" search_criteria ")" ;; New in IMAP4 search_old ::= "ALL" / "ANSWERED" / "BCC" SPACE astring / "BEFORE" SPACE date / "BODY" SPACE astring / "CC" SPACE astring / "DELETED" / "FLAGGED" / "FROM" SPACE astring / "KEYWORD" SPACE flag_keyword / "NEW" / "OLD" / "ON" SPACE date / "RECENT" / "SEEN" / "SINCE" SPACE date / "SUBJECT" SPACE astring / "TEXT" SPACE astring / "TO" SPACE astring / "UNANSWERED" / "UNDELETED" / "UNFLAGGED" / "UNKEYWORD" SPACE flag_keyword / "UNSEEN" ;; Defined in RFC-1176 section ::= number ["." section] select ::= "SELECT" SPACE mailbox server_data ::= "CAPABILITY" SPACE "IMAP4" [SPACE 1#capability] sequence ::= sequence_num / (sequence "," sequence) / (sequence_num ":" sequence_num) ;; Identifies a set of messages. For message ;; numbers, these are consecutive numbers from ;; 1 to the number of messages in the mailbox. ;; Comma delimits individual numbers, colon ;; delimits between two numbers inclusive. ;; Example: 2,4:7,9,12:* is 2,4,5,6,7,9,12,13, ;; 14,15 for a mailbox with 15 messages. sequence_num ::= number / "*" ;; * is the largest number in use. For message ;; numbers, it is the number of messages in the ;; mailbox. For unique identifiers, it is the ;; unique identifier of the last message in the ;; mailbox. SPACE ::= Crispin [Page 55] Internet DRAFT IMAP4 June 20, 1994 store ::= "STORE" SPACE sequence SPACE store_att_flags store_att_flags ::= (["+" / "-"] "FLAGS" [".SILENT"]) SPACE (flag_list / #flag) string ::= quoted / literal subscribe ::= "SUBSCRIBE" [SPACE "MAILBOX"] SPACE mailbox tag ::= 1* text ::= 1*TEXT_CHAR text_1522 ::= "=?" "?" "?" "?=" ;; Syntax defined in RFC 1522 TEXT_CHAR ::= time ::= 2digit ":" 2digit ":" 2digit ;; Hours minutes seconds uid ::= "UID" SPACE (copy / fetch / search / store) ;; Uniqueids used instead of message numbers uniqueid ::= number ;; Strictly ascending unsubscribe ::= "UNSUBSCRIBE" [SPACE "MAILBOX"] SPACE mailbox userid ::= astring x_command ::= "X" atom zone ::= ("+" / "-") 4digit ;; Signed four-digit value of hhmm representing ;; hours and minutes west of Greenwich (that is, ;; (the amount that the given time differs from ;; Universal Time). Subtracting the timezone ;; from the given time will give the UT form. ;; The Universal Time zone is "+0000". Crispin [Page 56] Internet DRAFT IMAP4 June 20, 1994 zone_old ::= "UT" / "GMT" / "Z" / ;; +0000 "AST" / "EST" / "CST" / "MST" / ;; -0400 to -0700 "PST" / "YST" / "HST" / "BST" / ;; -0800 to -1100 "ADT" / "EDT" / "CDT" / "MDT" / ;; -0300 to -0600 "PDT" / "YDT" / "HDT" / "BDT" / ;; -0700 to -1000 "A" / "B" / "C" / "D" / "E" / "F" / ;; +0100 to +0600 "G" / "H" / "I" / "K" / "L" / "M" / ;; +0700 to +1200 "N" / "O" / "P" / "Q" / "R" / "S" / ;; -0100 to -0600 "T" / "U" / "V" / "W" / "X" / "Y" ;; -0700 to -1200 ;; OBSOLETE Crispin [Page 57] Internet DRAFT IMAP4 June 20, 1994 Appendices A. Author's Note This document is a rewrite of earlier documents, and supercedes the protocol specification in those documents: earlier IMAP4 Internet drafts, the IMAP2bis Internet drafts, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064. B. Security Considerations IMAP4 protocol transactions, including electronic mail data, are sent in the clear over the network unless the optional privacy protection is negotiated in the AUTHENTICATE command. A server error message for an AUTHENTICATE command which fails due to invalid credentials should not detail why the credentials are invalid. Use of the LOGIN command sends passwords in the clear. This can be avoided by using the AUTHENTICATE command instead. A server error message for a failing LOGIN command should not specify that the user name, as opposed to the password, is invalid. Additional security considerations are discussed in the section discussing the AUTHENTICATE and LOGIN commands. C. Author's Address Mark R. Crispin Networks and Distributed Computing, JE-30 University of Washington Seattle, WA 98195 Phone: (206) 543-5762 EMail: MRC@CAC.Washington.EDU Crispin [Page 58] Internet DRAFT IMAP4 June 20, 1994 D. IMAP4 Keyword Index +FLAGS (store command data item) ............... 30 +FLAGS.SILENT (store command data item) ........ 30 -FLAGS (store command data item) ............... 30 -FLAGS.SILENT (store command data item) ........ 30 ALERT (special information token) .......................... 33 ALL (fetch item) ........................................... 25 ALL (search key) ........................................... 22 ANSWERED (search key) ...................................... 22 APPEND (command) ........................................... 18 AUTHENTICATE (command) ..................................... 8 BAD (response) ............................................. 35 BCC (search key) .................................. 22 BEFORE (search key) ................................. 22 BODY (fetch item) .......................................... 25 BODY (fetch result) ........................................ 41 BODY (search key) ................................. 22 BODY.PEEK[
] (fetch item) .......................... 26 BODYSTRUCTURE (fetch item) ................................. 26 BODYSTRUCTURE (fetch result) ............................... 41 BODY[
] (fetch item) ............................... 25 BODY[section] (fetch result) ............................... 41 BYE (response) ............................................. 36 CAPABILITY (command) ....................................... 6 CAPABILITY (response) ...................................... 37 CC (search key) ................................... 22 CHECK (command) ............................................ 19 CLOSE (command) ............................................ 20 COPY (command) ............................................. 30 COPY (response) ............................................ 45 CREATE (command) ........................................... 12 DELETE (command) ........................................... 12 DELETED (search key) ....................................... 23 DRAFT (search key) ......................................... 23 ENVELOPE (fetch item) ...................................... 26 ENVELOPE (fetch result) .................................... 43 EXAMINE (command) .......................................... 11 EXISTS (response) .......................................... 40 EXPUNGE (command) .......................................... 20 EXPUNGE (response) ......................................... 40 FAST (fetch item) .......................................... 26 FETCH (command) ............................................ 25 FETCH (response) ........................................... 40 FIND ALL.MAILBOXES (command) ............................... 16 FIND MAILBOXES (command) ................................... 17 FLAGGED (search key) ....................................... 23 FLAGS (fetch item) ......................................... 26 Crispin [Page 59] Internet DRAFT IMAP4 June 20, 1994 FLAGS (fetch result) ....................................... 44 FLAGS (response) ........................................... 39 FLAGS (store command data item) ................ 29 FLAGS.SILENT (store command data item) ......... 29 FROM (search key) ................................. 23 FULL (fetch item) .......................................... 27 HEADER (search key) .................. 23 INTERNALDATE (fetch item) .................................. 27 INTERNALDATE (fetch result) ................................ 44 KEYWORD (search key) ................................ 23 LARGER (search key) .................................... 23 LIST (command) ............................................. 14 LIST (response) ............................................ 37 LOGIN (command) ............................................ 9 LOGOUT (command) ........................................... 7 LSUB (command) ............................................. 16 LSUB (response) ............................................ 38 MAILBOX (response) ......................................... 38 NEW (search key) ........................................... 23 NO (response) .............................................. 35 NOOP (command) ............................................. 6 NOT (search key) .............................. 23 OK (response) .............................................. 34 OLD (search key) ........................................... 23 ON (search key) ..................................... 23 OR (search key) ................ 23 PARSE (special information token) .......................... 34 PARTIAL (command) .......................................... 28 PERMANENTFLAGS (special information token) ................. 34 PREAUTH (response) ......................................... 36 READ-ONLY (special information token) ...................... 34 READ-WRITE (special information token) ..................... 34 RECENT (response) .......................................... 40 RECENT (search key) ........................................ 23 RENAME (command) ........................................... 13 RFC822 (fetch item) ........................................ 27 RFC822 (fetch result) ...................................... 44 RFC822.HEADER (fetch item) ................................. 27 RFC822.HEADER (fetch result) ............................... 44 RFC822.HEADER.LINES (fetch item) ............. 27 RFC822.HEADER.LINES.NOT (fetch item) ......... 27 RFC822.PEEK (fetch item) ................................... 27 RFC822.SIZE (fetch item) ................................... 27 RFC822.SIZE (fetch result) ................................. 45 RFC822.TEXT (fetch item) ................................... 27 RFC822.TEXT (fetch result) ................................. 45 RFC822.TEXT.PEEK (fetch item) .............................. 28 SEARCH (command) ........................................... 21 Crispin [Page 60] Internet DRAFT IMAP4 June 20, 1994 SEARCH (response) .......................................... 39 SEEN (search key) .......................................... 23 SELECT (command) ........................................... 10 SENTBEFORE (search key) ............................. 23 SENTON (search key) ................................. 24 SENTSINCE (search key) .............................. 24 SINCE (search key) .................................. 24 SMALLER (search key) ................................... 24 STORE (command) ............................................ 29 STORE (response) ........................................... 45 SUBJECT (search key) .............................. 24 SUBSCRIBE (command) ........................................ 14 TEXT (search key) ................................. 24 TO (search key) ................................... 24 TRYCREATE (special information token) ...................... 34 UID (command) .............................................. 31 UID (fetch item) ........................................... 28 UID (fetch result) ......................................... 45 UID (search key) ................................ 24 UNANSWERED (search key) .................................... 24 UNDELETED (search key) ..................................... 24 UNDRAFT (search key) ....................................... 24 UNFLAGGED (search key) ..................................... 24 UNKEYWORD (search key) .............................. 24 UNSEEN (search key) ........................................ 24 UNSEEN (special information token) ......................... 34 UNSUBSCRIBE (command) ...................................... 14 X (command) .......................................... 32 \Answered (system flag) .................................... 44 \Deleted (system flag) ..................................... 44 \Draft (system flag) ....................................... 44 \Flagged (system flag) ..................................... 44 \Marked (mailbox name attribute) ........................... 37 \Noinferiors (mailbox name attribute) ...................... 37 \Noselect (mailbox name attribute) ......................... 37 \Recent (system flag) ...................................... 44 \Seen (system flag) ........................................ 44 \Unmarked (mailbox name attribute) ......................... 38 Crispin [Page 61]