RFC 2060
Internet Message Access Protocol - Version 4rev1
6. Client Commands IMAP4rev1 commands are described in this section. Commands are organized by the state in which the command is permitted. Commands which are permitted in multiple states are listed in the minimum
permitted state (for example, commands valid in authenticated and selected state are listed in the authenticated state commands). Command arguments, identified by "Arguments:" in the command descriptions below, are described by function, not by syntax. The precise syntax of command arguments is described in the Formal Syntax section. Some commands cause specific server responses to be returned; these are identified by "Responses:" in the command descriptions below. See the response descriptions in the Responses section for information on these responses, and the Formal Syntax section for the precise syntax of these responses. It is possible for server data to be transmitted as a result of any command; thus, commands that do not specifically require server data specify "no specific responses for this command" instead of "none". The "Result:" in the command description refers to the possible tagged status responses to a command, and any special interpretation of these status responses. 6.1. Client Commands - Any State The following commands are valid in any state: CAPABILITY, NOOP, and LOGOUT. 6.1.1. CAPABILITY Command Arguments: none Responses: REQUIRED untagged response: CAPABILITY Result: OK - capability completed BAD - command unknown or arguments invalid The CAPABILITY command requests a listing of capabilities that the server supports. The server MUST send a single untagged CAPABILITY response with "IMAP4rev1" as one of the listed capabilities before the (tagged) OK response. This listing of capabilities is not dependent upon connection state or user. It is therefore not necessary to issue a CAPABILITY command more than once in a connection.
A capability name which begins with "AUTH=" indicates that the
server supports that particular authentication mechanism. All
such names are, by definition, part of this specification. For
example, the authorization capability for an experimental
"blurdybloop" authenticator would be "AUTH=XBLURDYBLOOP" and not
"XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".
Other capability names refer to extensions, revisions, or
amendments to this specification. See the documentation of the
CAPABILITY response for additional information. No capabilities,
beyond the base IMAP4rev1 set defined in this specification, are
enabled without explicit client action to invoke the capability.
See the section entitled "Client Commands -
Experimental/Expansion" for information about the form of site or
implementation-specific capabilities.
Example: C: abcd CAPABILITY
S: * CAPABILITY IMAP4rev1 AUTH=KERBEROS_V4
S: abcd OK CAPABILITY completed
6.1.2. NOOP Command
Arguments: none
Responses: no specific responses for this command (but see below)
Result: OK - noop completed
BAD - command unknown or arguments invalid
The NOOP command always succeeds. It does nothing.
Since any command can return a status update as untagged data, the
NOOP command can be used as a periodic poll for new messages or
message status updates during a period of inactivity. The NOOP
command can also be used to reset any inactivity autologout timer
on the server.
Example: C: a002 NOOP
S: a002 OK NOOP completed
. . .
C: a047 NOOP
S: * 22 EXPUNGE
S: * 23 EXISTS
S: * 3 RECENT
S: * 14 FETCH (FLAGS (\Seen \Deleted))
S: a047 OK NOOP completed
6.1.3. LOGOUT Command Arguments: none Responses: REQUIRED untagged response: BYE Result: OK - logout completed BAD - command unknown or arguments invalid The LOGOUT command informs the server that the client is done with the connection. The server MUST send a BYE untagged response before the (tagged) OK response, and then close the network connection. Example: C: A023 LOGOUT S: * BYE IMAP4rev1 Server logging out S: A023 OK LOGOUT completed (Server and client then close the connection) 6.2. Client Commands - Non-Authenticated State In non-authenticated state, the AUTHENTICATE or LOGIN command establishes authentication and enter authenticated state. The AUTHENTICATE command provides a general mechanism for a variety of authentication techniques, whereas the LOGIN command uses the traditional user name and plaintext password pair. Server implementations MAY allow non-authenticated access to certain mailboxes. The convention is to use a LOGIN command with the userid "anonymous". A password is REQUIRED. It is implementation-dependent what requirements, if any, are placed on the password and what access restrictions are placed on anonymous users. Once authenticated (including as anonymous), it is not possible to re-enter non-authenticated state. In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), the following commands are valid in non-authenticated state: AUTHENTICATE and LOGIN.
6.2.1. AUTHENTICATE Command Arguments: authentication mechanism name Responses: continuation data can be requested Result: OK - authenticate completed, now in authenticated state NO - authenticate failure: unsupported authentication mechanism, credentials rejected BAD - command unknown or arguments invalid, authentication exchange cancelled The AUTHENTICATE command indicates an authentication mechanism, such as described in [IMAP-AUTH], to the server. If the server supports the requested authentication mechanism, it performs an authentication protocol exchange to authenticate and identify the client. It MAY also negotiate an OPTIONAL protection mechanism for subsequent protocol interactions. If the requested authentication mechanism is not supported, the server SHOULD reject the AUTHENTICATE command by sending a tagged NO response. The authentication protocol exchange consists of a series of server challenges and client answers that are specific to the authentication mechanism. A server challenge consists of a command continuation request response with the "+" token followed by a BASE64 encoded string. The client answer consists of a line consisting of a BASE64 encoded string. If the client wishes to cancel an authentication exchange, it issues a line with a single "*". If the server receives such an answer, it MUST reject the AUTHENTICATE command by sending a tagged BAD response. A protection mechanism provides integrity and privacy protection to the connection. If a protection mechanism is negotiated, it is applied to all subsequent data sent over the connection. The protection mechanism takes effect immediately following the CRLF that concludes the authentication exchange for the client, and the CRLF of the tagged OK response for the server. Once the protection mechanism is in effect, the stream of command and response octets is processed into buffers of ciphertext. Each buffer is transferred over the connection as a stream of octets prepended with a four octet field in network byte order that represents the length of the following data. The maximum ciphertext buffer length is defined by the protection mechanism. Authentication mechanisms are OPTIONAL. Protection mechanisms are also OPTIONAL; an authentication mechanism MAY be implemented without any protection mechanism. If an AUTHENTICATE command fails with a NO response, the client MAY try another
authentication mechanism by issuing another AUTHENTICATE command,
or MAY attempt to authenticate by using the LOGIN command. In
other words, the client MAY request authentication types in
decreasing order of preference, with the LOGIN command as a last
resort.
Example: S: * OK KerberosV4 IMAP4rev1 Server
C: A001 AUTHENTICATE KERBEROS_V4
S: + AmFYig==
C: BAcAQU5EUkVXLkNNVS5FRFUAOCAsho84kLN3/IJmrMG+25a4DT
+nZImJjnTNHJUtxAA+o0KPKfHEcAFs9a3CL5Oebe/ydHJUwYFd
WwuQ1MWiy6IesKvjL5rL9WjXUb9MwT9bpObYLGOKi1Qh
S: + or//EoAADZI=
C: DiAF5A4gA+oOIALuBkAAmw==
S: A001 OK Kerberos V4 authentication successful
Note: the line breaks in the first client answer are for editorial
clarity and are not in real authenticators.
6.2.2. LOGIN Command
Arguments: user name
password
Responses: no specific responses for this command
Result: OK - login completed, now in authenticated state
NO - login failure: user name or password rejected
BAD - command unknown or arguments invalid
The LOGIN command identifies the client to the server and carries
the plaintext password authenticating this user.
Example: C: a001 LOGIN SMITH SESAME
S: a001 OK LOGIN completed
6.3. Client Commands - Authenticated State
In authenticated state, commands that manipulate mailboxes as atomic
entities are permitted. Of these commands, the SELECT and EXAMINE
commands will select a mailbox for access and enter selected state.
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
the following commands are valid in authenticated state: SELECT,
EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
STATUS, and APPEND.
6.3.1. SELECT Command Arguments: mailbox name Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT OPTIONAL OK untagged responses: UNSEEN, PERMANENTFLAGS Result: OK - select completed, now in selected state NO - select failure, now in authenticated state: no such mailbox, can't access mailbox BAD - command unknown or arguments invalid The SELECT command selects a mailbox so that messages in the mailbox can be accessed. Before returning an OK to the client, the server MUST send the following untagged data to the client: FLAGS Defined flags in the mailbox. See the description of the FLAGS response for more detail. <n> EXISTS The number of messages in the mailbox. See the description of the EXISTS response for more detail. <n> RECENT The number of messages with the \Recent flag set. See the description of the RECENT response for more detail. OK [UIDVALIDITY <n>] The unique identifier validity value. See the description of the UID command for more detail. to define the initial state of the mailbox at the client. The server SHOULD also send an UNSEEN response code in an OK untagged response, indicating the message sequence number of the first unseen message in the mailbox. If the client can not change the permanent state of one or more of the flags listed in the FLAGS untagged response, the server SHOULD send a PERMANENTFLAGS response code in an OK untagged response, listing the flags that the client can change permanently. Only one mailbox can be selected at a time in a connection; simultaneous access to multiple mailboxes requires multiple connections. The SELECT command automatically deselects any currently selected mailbox before attempting the new selection. Consequently, if a mailbox is selected and a SELECT command that fails is attempted, no mailbox is selected.
If the client is permitted to modify the mailbox, the server
SHOULD prefix the text of the tagged OK response with the
"[READ-WRITE]" response code.
If the client is not permitted to modify the mailbox but is
permitted read access, the mailbox is selected as read-only, and
the server MUST prefix the text of the tagged OK response to
SELECT with the "[READ-ONLY]" response code. Read-only access
through SELECT differs from the EXAMINE command in that certain
read-only mailboxes MAY permit the change of permanent state on a
per-user (as opposed to global) basis. Netnews messages marked in
a server-based .newsrc file are an example of such per-user
permanent state that can be modified with read-only mailboxes.
Example: C: A142 SELECT INBOX
S: * 172 EXISTS
S: * 1 RECENT
S: * OK [UNSEEN 12] Message 12 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
S: A142 OK [READ-WRITE] SELECT completed
6.3.2. EXAMINE Command
Arguments: mailbox name
Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
OPTIONAL OK untagged responses: UNSEEN, PERMANENTFLAGS
Result: OK - examine completed, now in selected state
NO - examine failure, now in authenticated state: no
such mailbox, can't access mailbox
BAD - command unknown or arguments invalid
The EXAMINE command is identical to SELECT and returns the same
output; however, the selected mailbox is identified as read-only.
No changes to the permanent state of the mailbox, including
per-user state, are permitted.
The text of the tagged OK response to the EXAMINE command MUST
begin with the "[READ-ONLY]" response code.
Example: C: A932 EXAMINE blurdybloop
S: * 17 EXISTS
S: * 2 RECENT
S: * OK [UNSEEN 8] Message 8 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
S: A932 OK [READ-ONLY] EXAMINE completed
6.3.3. CREATE Command
Arguments: mailbox name
Responses: no specific responses for this command
Result: OK - create completed
NO - create failure: can't create mailbox with that name
BAD - command unknown or arguments invalid
The CREATE command creates a mailbox with the given name. An OK
response is returned only if a new mailbox with that name has been
created. It is an error to attempt to create INBOX or a mailbox
with a name that refers to an extant mailbox. Any error in
creation will return a tagged NO response.
If the mailbox name is suffixed with the server's hierarchy
separator character (as returned from the server by a LIST
command), this is a declaration that the client intends to create
mailbox names under this name in the hierarchy. Server
implementations that do not require this declaration MUST ignore
it.
If the server's hierarchy separator character appears elsewhere in
the name, the server SHOULD create any superior hierarchical names
that are needed for the CREATE command to complete successfully.
In other words, an attempt to create "foo/bar/zap" on a server in
which "/" is the hierarchy separator character SHOULD create foo/
and foo/bar/ if they do not already exist.
If a new mailbox is created with the same name as a mailbox which
was deleted, its unique identifiers MUST be greater than any
unique identifiers used in the previous incarnation of the mailbox
UNLESS the new incarnation has a different unique identifier
validity value. See the description of the UID command for more
detail.
Example: C: A003 CREATE owatagusiam/
S: A003 OK CREATE completed
C: A004 CREATE owatagusiam/blurdybloop
S: A004 OK CREATE completed
Note: the interpretation of this example depends on whether "/"
was returned as the hierarchy separator from LIST. If "/" is the
hierarchy separator, a new level of hierarchy named "owatagusiam"
with a member called "blurdybloop" is created. Otherwise, two
mailboxes at the same hierarchy level are created.
6.3.4. DELETE Command
Arguments: mailbox name
Responses: no specific responses for this command
Result: OK - delete completed
NO - delete failure: can't delete mailbox with that name
BAD - command unknown or arguments invalid
The DELETE command permanently removes the mailbox with the given
name. A tagged OK response is returned only if the mailbox has
been deleted. It is an error to attempt to delete INBOX or a
mailbox name that does not exist.
The DELETE command MUST NOT remove inferior hierarchical names.
For example, if a mailbox "foo" has an inferior "foo.bar"
(assuming "." is the hierarchy delimiter character), removing
"foo" MUST NOT remove "foo.bar". It is an error to attempt to
delete a name that has inferior hierarchical names and also has
the \Noselect mailbox name attribute (see the description of the
LIST response for more details).
It is permitted to delete a name that has inferior hierarchical
names and does not have the \Noselect mailbox name attribute. In
this case, all messages in that mailbox are removed, and the name
will acquire the \Noselect mailbox name attribute.
The value of the highest-used unique identifier of the deleted
mailbox MUST be preserved so that a new mailbox created with the
same name will not reuse the identifiers of the former
incarnation, UNLESS the new incarnation has a different unique
identifier validity value. See the description of the UID command
for more detail.
Examples: C: A682 LIST "" *
S: * LIST () "/" blurdybloop
S: * LIST (\Noselect) "/" foo
S: * LIST () "/" foo/bar
S: A682 OK LIST completed
C: A683 DELETE blurdybloop
S: A683 OK DELETE completed
C: A684 DELETE foo
S: A684 NO Name "foo" has inferior hierarchical names
C: A685 DELETE foo/bar
S: A685 OK DELETE Completed
C: A686 LIST "" *
S: * LIST (\Noselect) "/" foo
S: A686 OK LIST completed
C: A687 DELETE foo
S: A687 OK DELETE Completed
C: A82 LIST "" *
S: * LIST () "." blurdybloop
S: * LIST () "." foo
S: * LIST () "." foo.bar
S: A82 OK LIST completed
C: A83 DELETE blurdybloop
S: A83 OK DELETE completed
C: A84 DELETE foo
S: A84 OK DELETE Completed
C: A85 LIST "" *
S: * LIST () "." foo.bar
S: A85 OK LIST completed
C: A86 LIST "" %
S: * LIST (\Noselect) "." foo
S: A86 OK LIST completed
6.3.5. RENAME Command
Arguments: existing mailbox name
new mailbox name
Responses: no specific responses for this command
Result: OK - rename completed
NO - rename failure: can't rename mailbox with that name,
can't rename to mailbox with that name
BAD - command unknown or arguments invalid
The RENAME command changes the name of a mailbox. A tagged OK
response is returned only if the mailbox has been renamed. It is
an error to attempt to rename from a mailbox name that does not
exist or to a mailbox name that already exists. Any error in
renaming will return a tagged NO response.
If the name has inferior hierarchical names, then the inferior
hierarchical names MUST also be renamed. For example, a rename of
"foo" to "zap" will rename "foo/bar" (assuming "/" is the
hierarchy delimiter character) to "zap/bar".
The value of the highest-used unique identifier of the old mailbox
name MUST be preserved so that a new mailbox created with the same
name will not reuse the identifiers of the former incarnation,
UNLESS the new incarnation has a different unique identifier
validity value. See the description of the UID command for more
detail.
Renaming INBOX is permitted, and has special behavior. It moves
all messages in INBOX to a new mailbox with the given name,
leaving INBOX empty. If the server implementation supports
inferior hierarchical names of INBOX, these are unaffected by a
rename of INBOX.
Examples: C: A682 LIST "" *
S: * LIST () "/" blurdybloop
S: * LIST (\Noselect) "/" foo
S: * LIST () "/" foo/bar
S: A682 OK LIST completed
C: A683 RENAME blurdybloop sarasoop
S: A683 OK RENAME completed
C: A684 RENAME foo zowie
S: A684 OK RENAME Completed
C: A685 LIST "" *
S: * LIST () "/" sarasoop
S: * LIST (\Noselect) "/" zowie
S: * LIST () "/" zowie/bar
S: A685 OK LIST completed
C: Z432 LIST "" *
S: * LIST () "." INBOX
S: * LIST () "." INBOX.bar
S: Z432 OK LIST completed
C: Z433 RENAME INBOX old-mail
S: Z433 OK RENAME completed
C: Z434 LIST "" *
S: * LIST () "." INBOX
S: * LIST () "." INBOX.bar
S: * LIST () "." old-mail
S: Z434 OK LIST completed
6.3.6. SUBSCRIBE Command
Arguments: mailbox
Responses: no specific responses for this command
Result: OK - subscribe completed
NO - subscribe failure: can't subscribe to that name
BAD - command unknown or arguments invalid
The SUBSCRIBE command adds the specified mailbox name to the
server's set of "active" or "subscribed" mailboxes as returned by
the LSUB command. This command returns a tagged OK response only
if the subscription is successful.
A server MAY validate the mailbox argument to SUBSCRIBE to verify
that it exists. However, it MUST NOT unilaterally remove an
existing mailbox name from the subscription list even if a mailbox
by that name no longer exists.
Note: this requirement is because some server sites may routinely
remove a mailbox with a well-known name (e.g. "system-alerts")
after its contents expire, with the intention of recreating it
when new contents are appropriate.
Example: C: A002 SUBSCRIBE #news.comp.mail.mime
S: A002 OK SUBSCRIBE completed
6.3.7. UNSUBSCRIBE Command Arguments: mailbox name Responses: no specific responses for this command Result: OK - unsubscribe completed NO - unsubscribe failure: can't unsubscribe that name BAD - command unknown or arguments invalid The UNSUBSCRIBE command removes the specified mailbox name from the server's set of "active" or "subscribed" mailboxes as returned by the LSUB command. This command returns a tagged OK response only if the unsubscription is successful. Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime S: A002 OK UNSUBSCRIBE completed 6.3..8. LIST Command Arguments: reference name mailbox name with possible wildcards Responses: untagged responses: LIST Result: OK - list completed NO - list failure: can't list that reference or name BAD - command unknown or arguments invalid The LIST command returns a subset of names from the complete set of all names available to the client. Zero or more untagged LIST replies are returned, containing the name attributes, hierarchy delimiter, and name; see the description of the LIST reply for more detail. The LIST command SHOULD return its data quickly, without undue delay. For example, it SHOULD NOT go to excess trouble to calculate \Marked or \Unmarked status or perform other processing; if each name requires 1 second of processing, then a list of 1200 names would take 20 minutes! An empty ("" string) reference name argument indicates that the mailbox name is interpreted as by SELECT. The returned mailbox names MUST match the supplied mailbox name pattern. A non-empty reference name argument is the name of a mailbox or a level of mailbox hierarchy, and indicates a context in which the mailbox name is interpreted in an implementation-defined manner.
An empty ("" string) mailbox name argument is a special request to
return the hierarchy delimiter and the root name of the name given
in the reference. The value returned as the root MAY be null if
the reference is non-rooted or is null. In all cases, the
hierarchy delimiter is returned. This permits a client to get the
hierarchy delimiter even when no mailboxes by that name currently
exist.
The reference and mailbox name arguments are interpreted, in an
implementation-dependent fashion, into a canonical form that
represents an unambiguous left-to-right hierarchy. The returned
mailbox names will be in the interpreted form.
Any part of the reference argument that is included in the
interpreted form SHOULD prefix the interpreted form. It SHOULD
also be in the same form as the reference name argument. This
rule permits the client to determine if the returned mailbox name
is in the context of the reference argument, or if something about
the mailbox argument overrode the reference argument. Without
this rule, the client would have to have knowledge of the server's
naming semantics including what characters are "breakouts" that
override a naming context.
For example, here are some examples of how references and mailbox
names might be interpreted on a UNIX-based server:
Reference Mailbox Name Interpretation
------------ ------------ --------------
~smith/Mail/ foo.* ~smith/Mail/foo.*
archive/ % archive/%
#news. comp.mail.* #news.comp.mail.*
~smith/Mail/ /usr/doc/foo /usr/doc/foo
archive/ ~fred/Mail/* ~fred/Mail/*
The first three examples demonstrate interpretations in the
context of the reference argument. Note that "~smith/Mail" SHOULD
NOT be transformed into something like "/u2/users/smith/Mail", or
it would be impossible for the client to determine that the
interpretation was in the context of the reference.
The character "*" is a wildcard, and matches zero or more
characters at this position. The character "%" is similar to "*",
but it does not match a hierarchy delimiter. If the "%" wildcard
is the last character of a mailbox name argument, matching levels
of hierarchy are also returned. If these levels of hierarchy are
not also selectable mailboxes, they are returned with the
\Noselect mailbox name attribute (see the description of the LIST
response for more details).
Server implementations are permitted to "hide" otherwise
accessible mailboxes from the wildcard characters, by preventing
certain characters or names from matching a wildcard in certain
situations. For example, a UNIX-based server might restrict the
interpretation of "*" so that an initial "/" character does not
match.
The special name INBOX is included in the output from LIST, if
INBOX is supported by this server for this user and if the
uppercase string "INBOX" matches the interpreted reference and
mailbox name arguments with wildcards as described above. The
criteria for omitting INBOX is whether SELECT INBOX will return
failure; it is not relevant whether the user's real INBOX resides
on this or some other server.
Example: C: A101 LIST "" ""
S: * LIST (\Noselect) "/" ""
S: A101 OK LIST Completed
C: A102 LIST #news.comp.mail.misc ""
S: * LIST (\Noselect) "." #news.
S: A102 OK LIST Completed
C: A103 LIST /usr/staff/jones ""
S: * LIST (\Noselect) "/" /
S: A103 OK LIST Completed
C: A202 LIST ~/Mail/ %
S: * LIST (\Noselect) "/" ~/Mail/foo
S: * LIST () "/" ~/Mail/meetings
S: A202 OK LIST completed
6.3.9. LSUB Command
Arguments: reference name
mailbox name with possible wildcards
Responses: untagged responses: LSUB
Result: OK - lsub completed
NO - lsub failure: can't list that reference or name
BAD - command unknown or arguments invalid
The LSUB command returns a subset of names from the set of names
that the user has declared as being "active" or "subscribed".
Zero or more untagged LSUB replies are returned. The arguments to
LSUB are in the same form as those for LIST.
A server MAY validate the subscribed names to see if they still
exist. If a name does not exist, it SHOULD be flagged with the
\Noselect attribute in the LSUB response. The server MUST NOT
unilaterally remove an existing mailbox name from the subscription
list even if a mailbox by that name no longer exists.
Example: C: A002 LSUB "#news." "comp.mail.*"
S: * LSUB () "." #news.comp.mail.mime
S: * LSUB () "." #news.comp.mail.misc
S: A002 OK LSUB completed
6.3.10. STATUS Command
Arguments: mailbox name
status data item names
Responses: untagged responses: STATUS
Result: OK - status completed
NO - status failure: no status for that name
BAD - command unknown or arguments invalid
The STATUS command requests the status of the indicated mailbox.
It does not change the currently selected mailbox, nor does it
affect the state of any messages in the queried mailbox (in
particular, STATUS MUST NOT cause messages to lose the \Recent
flag).
The STATUS command provides an alternative to opening a second
IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
query that mailbox's status without deselecting the current
mailbox in the first IMAP4rev1 connection.
Unlike the LIST command, the STATUS command is not guaranteed to
be fast in its response. In some implementations, the server is
obliged to open the mailbox read-only internally to obtain certain
status information. Also unlike the LIST command, the STATUS
command does not accept wildcards.
The currently defined status data items that can be requested are:
MESSAGES The number of messages in the mailbox.
RECENT The number of messages with the \Recent flag set.
UIDNEXT The next UID value that will be assigned to a new
message in the mailbox. It is guaranteed that this
value will not change unless new messages are added
to the mailbox; and that it will change when new
messages are added even if those new messages are
subsequently expunged.
UIDVALIDITY The unique identifier validity value of the
mailbox.
UNSEEN The number of messages which do not have the \Seen
flag set.
Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES)
S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
S: A042 OK STATUS completed
6.3.11. APPEND Command
Arguments: mailbox name
OPTIONAL flag parenthesized list
OPTIONAL date/time string
message literal
Responses: no specific responses for this command
Result: OK - append completed
NO - append error: can't append to that mailbox, error
in flags or date/time or message text
BAD - command unknown or arguments invalid
The APPEND command appends the literal argument as a new message
to the end of the specified destination mailbox. This argument
SHOULD be in the format of an [RFC-822] message. 8-bit characters
are permitted in the message. A server implementation that is
unable to preserve 8-bit data properly MUST be able to reversibly
convert 8-bit APPEND data to 7-bit using a [MIME-IMB] content
transfer encoding.
Note: There MAY be exceptions, e.g. draft messages, in which
required [RFC-822] header lines are omitted in the message literal
argument to APPEND. The full implications of doing so MUST be
understood and carefully weighed.
If a flag parenthesized list is specified, the flags SHOULD be set in
the resulting message; otherwise, the flag list of the resulting
message is set empty by default.
If a date_time is specified, the internal date SHOULD be set in the
resulting message; otherwise, the internal date of the resulting
message is set to the current date and time by default.
If the append is unsuccessful for any reason, the mailbox MUST be
restored to its state before the APPEND attempt; no partial appending
is permitted.
If the destination mailbox does not exist, a server MUST return an
error, and MUST NOT automatically create the mailbox. Unless it is
certain that the destination mailbox can not be created, the server
MUST send the response code "[TRYCREATE]" as the prefix of the text
of the tagged NO response. This gives a hint to the client that it
can attempt a CREATE command and retry the APPEND if the CREATE is
successful.
If the mailbox is currently selected, the normal new mail actions
SHOULD occur. Specifically, the server SHOULD notify the client
immediately via an untagged EXISTS response. If the server does not
do so, the client MAY issue a NOOP command (or failing that, a CHECK
command) after one or more APPEND commands.
Example: C: A003 APPEND saved-messages (\Seen) {310}
C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
C: From: Fred Foobar <foobar@Blurdybloop.COM>
C: Subject: afternoon meeting
C: To: mooch@owatagu.siam.edu
C: Message-Id: <B27397-0100000@Blurdybloop.COM>
C: MIME-Version: 1.0
C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
C:
C: Hello Joe, do you think we can meet at 3:30 tomorrow?
C:
S: A003 OK APPEND completed
Note: the APPEND command is not used for message delivery, because
it does not provide a mechanism to transfer [SMTP] envelope
information.
6.4. Client Commands - Selected State
In selected state, commands that manipulate messages in a mailbox are
permitted.
In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
and the authenticated state commands (SELECT, EXAMINE, CREATE,
DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, STATUS, and
APPEND), the following commands are valid in the selected state:
CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.
6.4.1. CHECK Command Arguments: none Responses: no specific responses for this command Result: OK - check completed BAD - command unknown or arguments invalid The CHECK command requests a checkpoint of the currently selected mailbox. A checkpoint refers to any implementation-dependent housekeeping associated with the mailbox (e.g. resolving the server's in-memory state of the mailbox with the state on its disk) that is not normally executed as part of each command. A checkpoint MAY take a non-instantaneous amount of real time to complete. If a server implementation has no such housekeeping considerations, CHECK is equivalent to NOOP. There is no guarantee that an EXISTS untagged response will happen as a result of CHECK. NOOP, not CHECK, SHOULD be used for new mail polling. Example: C: FXXZ CHECK S: FXXZ OK CHECK Completed 6.4.2. CLOSE Command Arguments: none Responses: no specific responses for this command Result: OK - close completed, now in authenticated state NO - close failure: no mailbox selected BAD - command unknown or arguments invalid The CLOSE command permanently removes from the currently selected mailbox all messages that have the \Deleted flag set, and returns to authenticated state from selected state. No untagged EXPUNGE responses are sent. No messages are removed, and no error is given, if the mailbox is selected by an EXAMINE command or is otherwise selected read-only. Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT command MAY be issued without previously issuing a CLOSE command. The SELECT, EXAMINE, and LOGOUT commands implicitly close the currently selected mailbox without doing an expunge. However, when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT
sequence is considerably faster than an EXPUNGE-LOGOUT or
EXPUNGE-SELECT because no untagged EXPUNGE responses (which the
client would probably ignore) are sent.
Example: C: A341 CLOSE
S: A341 OK CLOSE completed
6.4.3. EXPUNGE Command
Arguments: none
Responses: untagged responses: EXPUNGE
Result: OK - expunge completed
NO - expunge failure: can't expunge (e.g. permission
denied)
BAD - command unknown or arguments invalid
The EXPUNGE command permanently removes from the currently
selected mailbox all messages that have the \Deleted flag set.
Before returning an OK to the client, an untagged EXPUNGE response
is sent for each message that is removed.
Example: C: A202 EXPUNGE
S: * 3 EXPUNGE
S: * 3 EXPUNGE
S: * 5 EXPUNGE
S: * 8 EXPUNGE
S: A202 OK EXPUNGE completed
Note: in this example, messages 3, 4, 7, and 11 had the
\Deleted flag set. See the description of the EXPUNGE
response for further explanation.
6.4.4. SEARCH Command
Arguments: OPTIONAL [CHARSET] specification
searching criteria (one or more)
Responses: REQUIRED untagged response: SEARCH
Result: OK - search completed
NO - search error: can't search that [CHARSET] or
criteria
BAD - command unknown or arguments invalid
The SEARCH command searches the mailbox for messages that match
the given searching criteria. Searching criteria consist of one
or more search keys. The untagged SEARCH response from the server
contains a listing of message sequence numbers corresponding to
those messages that match the searching criteria.
When multiple keys are specified, the result is the intersection
(AND function) of all the messages that match those keys. For
example, the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers
to all deleted messages from Smith that were placed in the mailbox
since February 1, 1994. A search key can also be a parenthesized
list of one or more search keys (e.g. for use with the OR and NOT
keys).
Server implementations MAY exclude [MIME-IMB] body parts with
terminal content media types other than TEXT and MESSAGE from
consideration in SEARCH matching.
The OPTIONAL [CHARSET] specification consists of the word
"CHARSET" followed by a registered [CHARSET]. It indicates the
[CHARSET] of the strings that appear in the search criteria.
[MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
[RFC-822]/[MIME-IMB] headers, MUST be decoded before comparing
text in a [CHARSET] other than US-ASCII. US-ASCII MUST be
supported; other [CHARSET]s MAY be supported. If the server does
not support the specified [CHARSET], it MUST return a tagged NO
response (not a BAD).
In all search keys that use strings, a message matches the key if
the string is a substring of the field. The matching is case-
insensitive.
The defined search keys are as follows. Refer to the Formal
Syntax section for the precise syntactic definitions of the
arguments.
<message set> Messages with message sequence numbers
corresponding to the specified message sequence
number set
ALL All messages in the mailbox; the default initial
key for ANDing.
ANSWERED Messages with the \Answered flag set.
BCC <string> Messages that contain the specified string in the
envelope structure's BCC field.
BEFORE <date> Messages whose internal date is earlier than the
specified date.
BODY <string> Messages that contain the specified string in the
body of the message.
CC <string> Messages that contain the specified string in the
envelope structure's CC field.
DELETED Messages with the \Deleted flag set.
DRAFT Messages with the \Draft flag set.
FLAGGED Messages with the \Flagged flag set.
FROM <string> Messages that contain the specified string in the
envelope structure's FROM field.
HEADER <field-name> <string>
Messages that have a header with the specified
field-name (as defined in [RFC-822]) and that
contains the specified string in the [RFC-822]
field-body.
KEYWORD <flag> Messages with the specified keyword set.
LARGER <n> Messages with an [RFC-822] size larger than the
specified number of octets.
NEW Messages that have the \Recent flag set but not the
\Seen flag. This is functionally equivalent to
"(RECENT UNSEEN)".
NOT <search-key>
Messages that do not match the specified search
key.
OLD Messages that do not have the \Recent flag set.
This is functionally equivalent to "NOT RECENT" (as
opposed to "NOT NEW").
ON <date> Messages whose internal date is within the
specified date.
OR <search-key1> <search-key2>
Messages that match either search key.
RECENT Messages that have the \Recent flag set.
SEEN Messages that have the \Seen flag set.
SENTBEFORE <date>
Messages whose [RFC-822] Date: header is earlier
than the specified date.
SENTON <date> Messages whose [RFC-822] Date: header is within the
specified date.
SENTSINCE <date>
Messages whose [RFC-822] Date: header is within or
later than the specified date.
SINCE <date> Messages whose internal date is within or later
than the specified date.
SMALLER <n> Messages with an [RFC-822] size smaller than the
specified number of octets.
SUBJECT <string>
Messages that contain the specified string in the
envelope structure's SUBJECT field.
TEXT <string> Messages that contain the specified string in the
header or body of the message.
TO <string> Messages that contain the specified string in the
envelope structure's TO field.
UID <message set>
Messages with unique identifiers corresponding to
the specified unique identifier set.
UNANSWERED Messages that do not have the \Answered flag set.
UNDELETED Messages that do not have the \Deleted flag set.
UNDRAFT Messages that do not have the \Draft flag set.
UNFLAGGED Messages that do not have the \Flagged flag set.
UNKEYWORD <flag>
Messages that do not have the specified keyword
set.
UNSEEN Messages that do not have the \Seen flag set.
Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
S: * SEARCH 2 84 882
S: A282 OK SEARCH completed
6.4.5. FETCH Command
Arguments: message set
message data item names
Responses: untagged responses: FETCH
Result: OK - fetch completed
NO - fetch error: can't fetch that data
BAD - command unknown or arguments invalid
The FETCH command retrieves data associated with a message in the
mailbox. The data items to be fetched can be either a single atom
or a parenthesized list.
The currently defined data items that can be fetched are:
ALL Macro equivalent to: (FLAGS INTERNALDATE
RFC822.SIZE ENVELOPE)
BODY Non-extensible form of BODYSTRUCTURE.
BODY[<section>]<<partial>>
The text of a particular body section. The section
specification is a set of zero or more part
specifiers delimited by periods. A part specifier
is either a part number or one of the following:
HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, MIME, and
TEXT. An empty section specification refers to the
entire message, including the header.
Every message has at least one part number.
Non-[MIME-IMB] messages, and non-multipart
[MIME-IMB] messages with no encapsulated message,
only have a part 1.
Multipart messages are assigned consecutive part
numbers, as they occur in the message. If a
particular part is of type message or multipart,
its parts MUST be indicated by a period followed by
the part number within that nested multipart part.
A part of type MESSAGE/RFC822 also has nested part
numbers, referring to parts of the MESSAGE part's
body.
The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and
TEXT part specifiers can be the sole part specifier
or can be prefixed by one or more numeric part
specifiers, provided that the numeric part
specifier refers to a part of type MESSAGE/RFC822.
The MIME part specifier MUST be prefixed by one or
more numeric part specifiers.
The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT
part specifiers refer to the [RFC-822] header of
the message or of an encapsulated [MIME-IMT]
MESSAGE/RFC822 message. HEADER.FIELDS and
HEADER.FIELDS.NOT are followed by a list of
field-name (as defined in [RFC-822]) names, and
return a subset of the header. The subset returned
by HEADER.FIELDS contains only those header fields
with a field-name that matches one of the names in
the list; similarly, the subset returned by
HEADER.FIELDS.NOT contains only the header fields
with a non-matching field-name. The field-matching
is case-insensitive but otherwise exact. In all
cases, the delimiting blank line between the header
and the body is always included.
The MIME part specifier refers to the [MIME-IMB]
header for this part.
The TEXT part specifier refers to the text body of
the message, omitting the [RFC-822] header.
Here is an example of a complex message
with some of its part specifiers:
HEADER ([RFC-822] header of the message)
TEXT MULTIPART/MIXED
1 TEXT/PLAIN
2 APPLICATION/OCTET-STREAM
3 MESSAGE/RFC822
3.HEADER ([RFC-822] header of the message)
3.TEXT ([RFC-822] text body of the message)
3.1 TEXT/PLAIN
3.2 APPLICATION/OCTET-STREAM
4 MULTIPART/MIXED
4.1 IMAGE/GIF
4.1.MIME ([MIME-IMB] header for the IMAGE/GIF)
4.2 MESSAGE/RFC822
4.2.HEADER ([RFC-822] header of the message)
4.2.TEXT ([RFC-822] text body of the message)
4.2.1 TEXT/PLAIN
4.2.2 MULTIPART/ALTERNATIVE
4.2.2.1 TEXT/PLAIN
4.2.2.2 TEXT/RICHTEXT
It is possible to fetch a substring of the
designated text. This is done by appending an open
angle bracket ("<"), the octet position of the
first desired octet, a period, the maximum number
of octets desired, and a close angle bracket (">")
to the part specifier. If the starting octet is
beyond the end of the text, an empty string is
returned.
Any partial fetch that attempts to read beyond the
end of the text is truncated as appropriate. A
partial fetch that starts at octet 0 is returned as
a partial fetch, even if this truncation happened.
Note: this means that BODY[]<0.2048> of a
1500-octet message will return BODY[]<0>
with a literal of size 1500, not BODY[].
Note: a substring fetch of a
HEADER.FIELDS or HEADER.FIELDS.NOT part
specifier is calculated after subsetting
the header.
The \Seen flag is implicitly set; if this causes
the flags to change they SHOULD be included as part
of the FETCH responses.
BODY.PEEK[<section>]<<partial>>
An alternate form of BODY[<section>] that does not
implicitly set the \Seen flag.
BODYSTRUCTURE The [MIME-IMB] body structure of the message. This
is computed by the server by parsing the [MIME-IMB]
header fields in the [RFC-822] header and
[MIME-IMB] headers.
ENVELOPE The envelope structure of the message. This is
computed by the server by parsing the [RFC-822]
header into the component parts, defaulting various
fields as necessary.
FAST Macro equivalent to: (FLAGS INTERNALDATE
RFC822.SIZE)
FLAGS The flags that are set for this message.
FULL Macro equivalent to: (FLAGS INTERNALDATE
RFC822.SIZE ENVELOPE BODY)
INTERNALDATE The internal date of the message.
RFC822 Functionally equivalent to BODY[], differing in the
syntax of the resulting untagged FETCH data (RFC822
is returned).
RFC822.HEADER Functionally equivalent to BODY.PEEK[HEADER],
differing in the syntax of the resulting untagged
FETCH data (RFC822.HEADER is returned).
RFC822.SIZE The [RFC-822] size of the message.
RFC822.TEXT Functionally equivalent to BODY[TEXT], differing in
the syntax of the resulting untagged FETCH data
(RFC822.TEXT is returned).
UID The unique identifier for the message.
Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
S: * 2 FETCH ....
S: * 3 FETCH ....
S: * 4 FETCH ....
S: A654 OK FETCH completed
6.4.6. STORE Command
Arguments: message set
message data item name
value for message data item
Responses: untagged responses: FETCH
Result: OK - store completed
NO - store error: can't store that data
BAD - command unknown or arguments invalid
The STORE command alters data associated with a message in the
mailbox. Normally, STORE will return the updated value of the
data with an untagged FETCH response. A suffix of ".SILENT" in
the data item name prevents the untagged FETCH, and the server
SHOULD assume that the client has determined the updated value
itself or does not care about the updated value.
Note: regardless of whether or not the ".SILENT" suffix was
used, the server SHOULD send an untagged FETCH response if a
change to a message's flags from an external source is
observed. The intent is that the status of the flags is
determinate without a race condition.
The currently defined data items that can be stored are:
FLAGS <flag list>
Replace the flags for the message with the
argument. The new value of the flags are returned
as if a FETCH of those flags was done.
FLAGS.SILENT <flag list>
Equivalent to FLAGS, but without returning a new
value.
+FLAGS <flag list>
Add the argument to the flags for the message. The
new value of the flags are returned as if a FETCH
of those flags was done.
+FLAGS.SILENT <flag list>
Equivalent to +FLAGS, but without returning a new
value.
-FLAGS <flag list>
Remove the argument from the flags for the message.
The new value of the flags are returned as if a
FETCH of those flags was done.
-FLAGS.SILENT <flag list>
Equivalent to -FLAGS, but without returning a new
value.
Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
S: * 2 FETCH FLAGS (\Deleted \Seen)
S: * 3 FETCH FLAGS (\Deleted)
S: * 4 FETCH FLAGS (\Deleted \Flagged \Seen)
S: A003 OK STORE completed
6.4.7. COPY Command
Arguments: message set
mailbox name
Responses: no specific responses for this command
Result: OK - copy completed
NO - copy error: can't copy those messages or to that
name
BAD - command unknown or arguments invalid
The COPY command copies the specified message(s) to the end of the
specified destination mailbox. The flags and internal date of the
message(s) SHOULD be preserved in the copy.
If the destination mailbox does not exist, a server SHOULD return
an error. It SHOULD NOT automatically create the mailbox. Unless
it is certain that the destination mailbox can not be created, the
server MUST send the response code "[TRYCREATE]" as the prefix of
the text of the tagged NO response. This gives a hint to the
client that it can attempt a CREATE command and retry the COPY if
the CREATE is successful.
If the COPY command is unsuccessful for any reason, server
implementations MUST restore the destination mailbox to its state
before the COPY attempt.
Example: C: A003 COPY 2:4 MEETING
S: A003 OK COPY completed
6.4.8. UID Command
Arguments: command name
command arguments
Responses: untagged responses: FETCH, SEARCH
Result: OK - UID command completed
NO - UID command error
BAD - command unknown or arguments invalid
The UID command has two forms. In the first form, it takes as its
arguments a COPY, FETCH, or STORE command with arguments
appropriate for the associated command. However, the numbers in
the message set argument are unique identifiers instead of message
sequence numbers.
In the second form, the UID command takes a SEARCH command with
SEARCH command arguments. The interpretation of the arguments is
the same as with SEARCH; however, the numbers returned in a SEARCH
response for a UID SEARCH command are unique identifiers instead
of message sequence numbers. For example, the command UID SEARCH
1:100 UID 443:557 returns the unique identifiers corresponding to
the intersection of the message sequence number set 1:100 and the
UID set 443:557.
Message set ranges are permitted; however, there is no guarantee
that unique identifiers be contiguous. A non-existent unique
identifier within a message set range is ignored without any error
message generated.
The number after the "*" in an untagged FETCH response is always a
message sequence number, not a unique identifier, even for a UID
command response. However, server implementations MUST implicitly
include the UID message data item as part of any FETCH response
caused by a UID command, regardless of whether a UID was specified
as a message data item to the FETCH.
Example: C: A999 UID FETCH 4827313:4828442 FLAGS
S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
S: A999 UID FETCH completed
6.5. Client Commands - Experimental/Expansion
6.5.1. X<atom> Command
Arguments: implementation defined
Responses: implementation defined
Result: OK - command completed
NO - failure
BAD - command unknown or arguments invalid
Any command prefixed with an X is an experimental command.
Commands which are not part of this specification, a standard or
standards-track revision of this specification, or an IESG-
approved experimental protocol, MUST use the X prefix.
Any added untagged responses issued by an experimental command
MUST also be prefixed with an X. Server implementations MUST NOT
send any such untagged responses, unless the client requested it
by issuing the associated experimental command.
Example: C: a441 CAPABILITY
S: * CAPABILITY IMAP4rev1 AUTH=KERBEROS_V4 XPIG-LATIN
S: a441 OK CAPABILITY completed
C: A442 XPIG-LATIN
S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
S: A442 OK XPIG-LATIN ompleted-cay
(page 48 continued on part 3)
