21.15. imaplib — IMAP4 protocol client

Source code: Lib/imaplib.py

This module defines three classes, IMAP4, IMAP4_SSL and IMAP4_stream, which encapsulate a connection to an IMAP4 server and implement a large subset of the IMAP4rev1 client protocol as defined in RFC 2060. It is backward compatible with IMAP4 (RFC 1730) servers, but note that the STATUS command is not supported in IMAP4.

Three classes are provided by the imaplib module, IMAP4 is the base class:

class imaplib.IMAP4(host='', port=IMAP4_PORT)

This class implements the actual IMAP4 protocol. The connection is created and protocol version (IMAP4 or IMAP4rev1) is determined when the instance is initialized. If host is not specified, '' (the local host) is used. If port is omitted, the standard IMAP4 port (143) is used.

The IMAP4 class supports the with statement. When used like this, the IMAP4 LOGOUT command is issued automatically when the with statement exits. E.g.:

>>> from imaplib import IMAP4
>>> with IMAP4("domain.org") as M:
...     M.noop()
...
('OK', [b'Nothing Accomplished. d25if65hy903weo.87'])

在 3.5 版更改: 支持了 with 语句。

Three exceptions are defined as attributes of the IMAP4 class:

exception IMAP4.error

Exception raised on any errors. The reason for the exception is passed to the constructor as a string.

exception IMAP4.abort

IMAP4 server errors cause this exception to be raised. This is a sub-class of IMAP4.error. Note that closing the instance and instantiating a new one will usually allow recovery from this exception.

exception IMAP4.readonly

This exception is raised when a writable mailbox has its status changed by the server. This is a sub-class of IMAP4.error. Some other client now has write permission, and the mailbox will need to be re-opened to re-obtain write permission.

There’s also a subclass for secure connections:

class imaplib.IMAP4_SSL(host='', port=IMAP4_SSL_PORT, keyfile=None, certfile=None, ssl_context=None)

This is a subclass derived from IMAP4 that connects over an SSL encrypted socket (to use this class you need a socket module that was compiled with SSL support). If host is not specified, '' (the local host) is used. If port is omitted, the standard IMAP4-over-SSL port (993) is used. ssl_context is a ssl.SSLContext object which allows bundling SSL configuration options, certificates and private keys into a single (potentially long-lived) structure. Please read Security considerations for best practices.

keyfile and certfile are a legacy alternative to ssl_context - they can point to PEM-formatted private key and certificate chain files for the SSL connection. Note that the keyfile/certfile parameters are mutually exclusive with ssl_context, a ValueError is raised if keyfile/certfile is provided along with ssl_context.

在 3.3 版更改: ssl_context parameter added.

在 3.4 版更改: The class now supports hostname check with ssl.SSLContext.check_hostname and Server Name Indication (see ssl.HAS_SNI).

3.6 版后已移除: keyfile and certfile are deprecated in favor of ssl_context. Please use ssl.SSLContext.load_cert_chain() instead, or let ssl.create_default_context() select the system’s trusted CA certificates for you.

The second subclass allows for connections created by a child process:

class imaplib.IMAP4_stream(command)

This is a subclass derived from IMAP4 that connects to the stdin/stdout file descriptors created by passing command to subprocess.Popen().

The following utility functions are defined:

imaplib.Internaldate2tuple(datestr)

Parse an IMAP4 INTERNALDATE string and return corresponding local time. The return value is a time.struct_time tuple or None if the string has wrong format.

imaplib.Int2AP(num)

Converts an integer into a string representation using characters from the set [A .. P].

imaplib.ParseFlags(flagstr)

Converts an IMAP4 FLAGS response to a tuple of individual flags.

imaplib.Time2Internaldate(date_time)

Convert date_time to an IMAP4 INTERNALDATE representation. The return value is a string in the form: "DD-Mmm-YYYY HH:MM:SS +HHMM" (including double-quotes). The date_time argument can be a number (int or float) representing seconds since epoch (as returned by time.time()), a 9-tuple representing local time an instance of time.struct_time (as returned by time.localtime()), an aware instance of datetime.datetime, or a double-quoted string. In the last case, it is assumed to already be in the correct format.

Note that IMAP4 message numbers change as the mailbox changes; in particular, after an EXPUNGE command performs deletions the remaining messages are renumbered. So it is highly advisable to use UIDs instead, with the UID command.

At the end of the module, there is a test section that contains a more extensive example of usage.

参见

Documents describing the protocol, and sources and binaries for servers implementing it, can all be found at the University of Washington’s IMAP Information Center (https://www.washington.edu/imap/).

21.15.1. IMAP4 Objects

All IMAP4rev1 commands are represented by methods of the same name, either upper-case or lower-case.

All arguments to commands are converted to strings, except for AUTHENTICATE, and the last argument to APPEND which is passed as an IMAP4 literal. If necessary (the string contains IMAP4 protocol-sensitive characters and isn’t enclosed with either parentheses or double quotes) each string is quoted. However, the password argument to the LOGIN command is always quoted. If you want to avoid having an argument string quoted (eg: the flags argument to STORE) then enclose the string in parentheses (eg: r'(\Deleted)').

Each command returns a tuple: (type, [data, ...]) where type is usually 'OK' or 'NO', and data is either the text from the command response, or mandated results from the command. Each data is either a string, or a tuple. If a tuple, then the first part is the header of the response, and the second part contains the data (ie: ‘literal’ value).

The message_set options to commands below is a string specifying one or more messages to be acted upon. It may be a simple message number ('1'), a range of message numbers ('2:4'), or a group of non-contiguous ranges separated by commas ('1:3,6:9'). A range can contain an asterisk to indicate an infinite upper bound ('3:*').

An IMAP4 instance has the following methods:

IMAP4.append(mailbox, flags, date_time, message)

Append message to named mailbox.

IMAP4.authenticate(mechanism, authobject)

Authenticate command — requires response processing.

mechanism specifies which authentication mechanism is to be used - it should appear in the instance variable capabilities in the form AUTH=mechanism.

authobject must be a callable object:

data = authobject(response)

It will be called to process server continuation responses; the response argument it is passed will be bytes. It should return bytes data that will be base64 encoded and sent to the server. It should return None if the client abort response * should be sent instead.

在 3.5 版更改: string usernames and passwords are now encoded to utf-8 instead of being limited to ASCII.

IMAP4.check()

Checkpoint mailbox on server.

IMAP4.close()

Close currently selected mailbox. Deleted messages are removed from writable mailbox. This is the recommended command before LOGOUT.

IMAP4.copy(message_set, new_mailbox)

Copy message_set messages onto end of new_mailbox.

IMAP4.create(mailbox)

Create new mailbox named mailbox.

IMAP4.delete(mailbox)

Delete old mailbox named mailbox.

IMAP4.deleteacl(mailbox, who)

Delete the ACLs (remove any rights) set for who on mailbox.

IMAP4.enable(capability)

Enable capability (see RFC 5161). Most capabilities do not need to be enabled. Currently only the UTF8=ACCEPT capability is supported (see RFC 6855).

3.5 新版功能: The enable() method itself, and RFC 6855 support.

IMAP4.expunge()

Permanently remove deleted items from selected mailbox. Generates an EXPUNGE response for each deleted message. Returned data contains a list of EXPUNGE message numbers in order received.

IMAP4.fetch(message_set, message_parts)

Fetch (parts of) messages. message_parts should be a string of message part names enclosed within parentheses, eg: "(UID BODY[TEXT])". Returned data are tuples of message part envelope and data.

IMAP4.getacl(mailbox)

Get the ACLs for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.getannotation(mailbox, entry, attribute)

Retrieve the specified ANNOTATIONs for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.getquota(root)

Get the quota root’s resource usage and limits. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

IMAP4.getquotaroot(mailbox)

Get the list of quota roots for the named mailbox. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

IMAP4.list([directory[, pattern]])

List mailbox names in directory matching pattern. directory defaults to the top-level mail folder, and pattern defaults to match anything. Returned data contains a list of LIST responses.

IMAP4.login(user, password)

Identify the client using a plaintext password. The password will be quoted.

IMAP4.login_cram_md5(user, password)

Force use of CRAM-MD5 authentication when identifying the client to protect the password. Will only work if the server CAPABILITY response includes the phrase AUTH=CRAM-MD5.

IMAP4.logout()

Shutdown connection to server. Returns server BYE response.

IMAP4.lsub(directory='""', pattern='*')

List subscribed mailbox names in directory matching pattern. directory defaults to the top level directory and pattern defaults to match any mailbox. Returned data are tuples of message part envelope and data.

IMAP4.myrights(mailbox)

Show my ACLs for a mailbox (i.e. the rights that I have on mailbox).

IMAP4.namespace()

Returns IMAP namespaces as defined in RFC 2342.

IMAP4.noop()

Send NOOP to server.

IMAP4.open(host, port)

Opens socket to port at host. This method is implicitly called by the IMAP4 constructor. The connection objects established by this method will be used in the IMAP4.read(), IMAP4.readline(), IMAP4.send(), and IMAP4.shutdown() methods. You may override this method.

IMAP4.partial(message_num, message_part, start, length)

Fetch truncated part of a message. Returned data is a tuple of message part envelope and data.

IMAP4.proxyauth(user)

Assume authentication as user. Allows an authorised administrator to proxy into any user’s mailbox.

IMAP4.read(size)

Reads size bytes from the remote server. You may override this method.

IMAP4.readline()

Reads one line from the remote server. You may override this method.

IMAP4.recent()

Prompt server for an update. Returned data is None if no new messages, else value of RECENT response.

IMAP4.rename(oldmailbox, newmailbox)

Rename mailbox named oldmailbox to newmailbox.

IMAP4.response(code)

Return data for response code if received, or None. Returns the given code, instead of the usual type.

IMAP4.search(charset, criterion[, ...])

Search mailbox for matching messages. charset may be None, in which case no CHARSET will be specified in the request to the server. The IMAP protocol requires that at least one criterion be specified; an exception will be raised when the server returns an error. charset must be None if the UTF8=ACCEPT capability was enabled using the enable() command.

示例:

# M is a connected IMAP4 instance...
typ, msgnums = M.search(None, 'FROM', '"LDJ"')

# or:
typ, msgnums = M.search(None, '(FROM "LDJ")')
IMAP4.select(mailbox='INBOX', readonly=False)

Select a mailbox. Returned data is the count of messages in mailbox (EXISTS response). The default mailbox is 'INBOX'. If the readonly flag is set, modifications to the mailbox are not allowed.

IMAP4.send(data)

Sends data to the remote server. You may override this method.

IMAP4.setacl(mailbox, who, what)

Set an ACL for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.setannotation(mailbox, entry, attribute[, ...])

Set ANNOTATIONs for mailbox. The method is non-standard, but is supported by the Cyrus server.

IMAP4.setquota(root, limits)

Set the quota root’s resource limits. This method is part of the IMAP4 QUOTA extension defined in rfc2087.

IMAP4.shutdown()

Close connection established in open. This method is implicitly called by IMAP4.logout(). You may override this method.

IMAP4.socket()

Returns socket instance used to connect to server.

IMAP4.sort(sort_criteria, charset, search_criterion[, ...])

The sort command is a variant of search with sorting semantics for the results. Returned data contains a space separated list of matching message numbers.

Sort has two arguments before the search_criterion argument(s); a parenthesized list of sort_criteria, and the searching charset. Note that unlike search, the searching charset argument is mandatory. There is also a uid sort command which corresponds to sort the way that uid search corresponds to search. The sort command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria. It then returns the numbers of matching messages.

This is an IMAP4rev1 extension command.

IMAP4.starttls(ssl_context=None)

Send a STARTTLS command. The ssl_context argument is optional and should be a ssl.SSLContext object. This will enable encryption on the IMAP connection. Please read Security considerations for best practices.

3.2 新版功能.

在 3.4 版更改: The method now supports hostname check with ssl.SSLContext.check_hostname and Server Name Indication (see ssl.HAS_SNI).

IMAP4.status(mailbox, names)

Request named status conditions for mailbox.

IMAP4.store(message_set, command, flag_list)

Alters flag dispositions for messages in mailbox. command is specified by section 6.4.6 of RFC 2060 as being one of “FLAGS”, “+FLAGS”, or “-FLAGS”, optionally with a suffix of “.SILENT”.

For example, to set the delete flag on all messages:

typ, data = M.search(None, 'ALL')
for num in data[0].split():
   M.store(num, '+FLAGS', '\\Deleted')
M.expunge()

注解

Creating flags containing ‘]’ (for example: “[test]”) violates RFC 3501 (the IMAP protocol). However, imaplib has historically allowed creation of such tags, and popular IMAP servers, such as Gmail, accept and produce such flags. There are non-Python programs which also create such tags. Although it is an RFC violation and IMAP clients and servers are supposed to be strict, imaplib nonetheless continues to allow such tags to be created for backward compatibility reasons, and as of python 3.6, handles them if they are sent from the server, since this improves real-world compatibility.

IMAP4.subscribe(mailbox)

Subscribe to new mailbox.

IMAP4.thread(threading_algorithm, charset, search_criterion[, ...])

The thread command is a variant of search with threading semantics for the results. Returned data contains a space separated list of thread members.

Thread members consist of zero or more messages numbers, delimited by spaces, indicating successive parent and child.

Thread has two arguments before the search_criterion argument(s); a threading_algorithm, and the searching charset. Note that unlike search, the searching charset argument is mandatory. There is also a uid thread command which corresponds to thread the way that uid search corresponds to search. The thread command first searches the mailbox for messages that match the given searching criteria using the charset argument for the interpretation of strings in the searching criteria. It then returns the matching messages threaded according to the specified threading algorithm.

This is an IMAP4rev1 extension command.

IMAP4.uid(command, arg[, ...])

Execute command args with messages identified by UID, rather than message number. Returns response appropriate to command. At least one argument must be supplied; if none are provided, the server will return an error and an exception will be raised.

IMAP4.unsubscribe(mailbox)

Unsubscribe from old mailbox.

IMAP4.xatom(name[, ...])

Allow simple extension commands notified by server in CAPABILITY response.

The following attributes are defined on instances of IMAP4:

IMAP4.PROTOCOL_VERSION

The most recent supported protocol in the CAPABILITY response from the server.

IMAP4.debug

Integer value to control debugging output. The initialize value is taken from the module variable Debug. Values greater than three trace each command.

IMAP4.utf8_enabled

Boolean value that is normally False, but is set to True if an enable() command is successfully issued for the UTF8=ACCEPT capability.

3.5 新版功能.

21.15.2. IMAP4 Example

Here is a minimal example (without error checking) that opens a mailbox and retrieves and prints all messages:

import getpass, imaplib

M = imaplib.IMAP4()
M.login(getpass.getuser(), getpass.getpass())
M.select()
typ, data = M.search(None, 'ALL')
for num in data[0].split():
    typ, data = M.fetch(num, '(RFC822)')
    print('Message %s\n%s\n' % (num, data[0][1]))
M.close()
M.logout()