271 lines
10 KiB
ReStructuredText
271 lines
10 KiB
ReStructuredText
:mod:`smtpd` --- SMTP Server
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============================
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.. module:: smtpd
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:synopsis: A SMTP server implementation in Python.
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.. moduleauthor:: Barry Warsaw <barry@python.org>
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.. sectionauthor:: Moshe Zadka <moshez@moshez.org>
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**Source code:** :source:`Lib/smtpd.py`
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--------------
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This module offers several classes to implement SMTP (email) servers.
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Several server implementations are present; one is a generic
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do-nothing implementation, which can be overridden, while the other two offer
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specific mail-sending strategies.
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Additionally the SMTPChannel may be extended to implement very specific
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interaction behaviour with SMTP clients.
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The code supports :RFC:`5321`, plus the :rfc:`1870` SIZE and :rfc:`6531`
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SMTPUTF8 extensions.
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SMTPServer Objects
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------------------
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.. class:: SMTPServer(localaddr, remoteaddr, data_size_limit=33554432,\
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map=None, enable_SMTPUTF8=False, decode_data=False)
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Create a new :class:`SMTPServer` object, which binds to local address
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*localaddr*. It will treat *remoteaddr* as an upstream SMTP relayer. It
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inherits from :class:`asyncore.dispatcher`, and so will insert itself into
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:mod:`asyncore`'s event loop on instantiation.
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*data_size_limit* specifies the maximum number of bytes that will be
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accepted in a ``DATA`` command. A value of ``None`` or ``0`` means no
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limit.
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*map* is the socket map to use for connections (an initially empty
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dictionary is a suitable value). If not specified the :mod:`asyncore`
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global socket map is used.
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*enable_SMTPUTF8* determines whether the ``SMTPUTF8`` extension (as defined
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in :RFC:`6531`) should be enabled. The default is ``False``.
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When ``True``, ``SMTPUTF8`` is accepted as a parameter to the ``MAIL``
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command and when present is passed to :meth:`process_message` in the
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``kwargs['mail_options']`` list. *decode_data* and *enable_SMTPUTF8*
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cannot be set to ``True`` at the same time.
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*decode_data* specifies whether the data portion of the SMTP transaction
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should be decoded using UTF-8. When *decode_data* is ``False`` (the
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default), the server advertises the ``8BITMIME``
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extension (:rfc:`6152`), accepts the ``BODY=8BITMIME`` parameter to
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the ``MAIL`` command, and when present passes it to :meth:`process_message`
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in the ``kwargs['mail_options']`` list. *decode_data* and *enable_SMTPUTF8*
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cannot be set to ``True`` at the same time.
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.. method:: process_message(peer, mailfrom, rcpttos, data, **kwargs)
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Raise a :exc:`NotImplementedError` exception. Override this in subclasses to
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do something useful with this message. Whatever was passed in the
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constructor as *remoteaddr* will be available as the :attr:`_remoteaddr`
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attribute. *peer* is the remote host's address, *mailfrom* is the envelope
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originator, *rcpttos* are the envelope recipients and *data* is a string
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containing the contents of the e-mail (which should be in :rfc:`5321`
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format).
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If the *decode_data* constructor keyword is set to ``True``, the *data*
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argument will be a unicode string. If it is set to ``False``, it
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will be a bytes object.
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*kwargs* is a dictionary containing additional information. It is empty
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if ``decode_data=True`` was given as an init argument, otherwise
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it contains the following keys:
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*mail_options*:
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a list of all received parameters to the ``MAIL``
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command (the elements are uppercase strings; example:
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``['BODY=8BITMIME', 'SMTPUTF8']``).
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*rcpt_options*:
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same as *mail_options* but for the ``RCPT`` command.
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Currently no ``RCPT TO`` options are supported, so for now
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this will always be an empty list.
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Implementations of ``process_message`` should use the ``**kwargs``
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signature to accept arbitrary keyword arguments, since future feature
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enhancements may add keys to the kwargs dictionary.
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Return ``None`` to request a normal ``250 Ok`` response; otherwise
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return the desired response string in :RFC:`5321` format.
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.. attribute:: channel_class
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Override this in subclasses to use a custom :class:`SMTPChannel` for
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managing SMTP clients.
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.. versionadded:: 3.4
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The *map* constructor argument.
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.. versionchanged:: 3.5
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*localaddr* and *remoteaddr* may now contain IPv6 addresses.
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.. versionadded:: 3.5
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The *decode_data* and *enable_SMTPUTF8* constructor parameters, and the
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*kwargs* parameter to :meth:`process_message` when *decode_data* is
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``False``.
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.. versionchanged:: 3.6
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*decode_data* is now ``False`` by default.
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DebuggingServer Objects
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-----------------------
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.. class:: DebuggingServer(localaddr, remoteaddr)
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Create a new debugging server. Arguments are as per :class:`SMTPServer`.
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Messages will be discarded, and printed on stdout.
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PureProxy Objects
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-----------------
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.. class:: PureProxy(localaddr, remoteaddr)
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Create a new pure proxy server. Arguments are as per :class:`SMTPServer`.
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Everything will be relayed to *remoteaddr*. Note that running this has a good
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chance to make you into an open relay, so please be careful.
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MailmanProxy Objects
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--------------------
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.. class:: MailmanProxy(localaddr, remoteaddr)
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Create a new pure proxy server. Arguments are as per :class:`SMTPServer`.
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Everything will be relayed to *remoteaddr*, unless local mailman configurations
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knows about an address, in which case it will be handled via mailman. Note that
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running this has a good chance to make you into an open relay, so please be
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careful.
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SMTPChannel Objects
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-------------------
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.. class:: SMTPChannel(server, conn, addr, data_size_limit=33554432,\
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map=None, enable_SMTPUTF8=False, decode_data=False)
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Create a new :class:`SMTPChannel` object which manages the communication
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between the server and a single SMTP client.
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*conn* and *addr* are as per the instance variables described below.
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*data_size_limit* specifies the maximum number of bytes that will be
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accepted in a ``DATA`` command. A value of ``None`` or ``0`` means no
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limit.
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*enable_SMTPUTF8* determines whether the ``SMTPUTF8`` extension (as defined
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in :RFC:`6531`) should be enabled. The default is ``False``.
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*decode_data* and *enable_SMTPUTF8* cannot be set to ``True`` at the same
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time.
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A dictionary can be specified in *map* to avoid using a global socket map.
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*decode_data* specifies whether the data portion of the SMTP transaction
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should be decoded using UTF-8. The default is ``False``.
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*decode_data* and *enable_SMTPUTF8* cannot be set to ``True`` at the same
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time.
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To use a custom SMTPChannel implementation you need to override the
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:attr:`SMTPServer.channel_class` of your :class:`SMTPServer`.
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.. versionchanged:: 3.5
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The *decode_data* and *enable_SMTPUTF8* parameters were added.
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.. versionchanged:: 3.6
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*decode_data* is now ``False`` by default.
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The :class:`SMTPChannel` has the following instance variables:
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.. attribute:: smtp_server
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Holds the :class:`SMTPServer` that spawned this channel.
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.. attribute:: conn
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Holds the socket object connecting to the client.
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.. attribute:: addr
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Holds the address of the client, the second value returned by
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:func:`socket.accept <socket.socket.accept>`
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.. attribute:: received_lines
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Holds a list of the line strings (decoded using UTF-8) received from
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the client. The lines have their ``"\r\n"`` line ending translated to
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``"\n"``.
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.. attribute:: smtp_state
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Holds the current state of the channel. This will be either
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:attr:`COMMAND` initially and then :attr:`DATA` after the client sends
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a "DATA" line.
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.. attribute:: seen_greeting
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Holds a string containing the greeting sent by the client in its "HELO".
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.. attribute:: mailfrom
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Holds a string containing the address identified in the "MAIL FROM:" line
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from the client.
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.. attribute:: rcpttos
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Holds a list of strings containing the addresses identified in the
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"RCPT TO:" lines from the client.
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.. attribute:: received_data
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Holds a string containing all of the data sent by the client during the
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DATA state, up to but not including the terminating ``"\r\n.\r\n"``.
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.. attribute:: fqdn
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Holds the fully-qualified domain name of the server as returned by
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:func:`socket.getfqdn`.
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.. attribute:: peer
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Holds the name of the client peer as returned by ``conn.getpeername()``
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where ``conn`` is :attr:`conn`.
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The :class:`SMTPChannel` operates by invoking methods named ``smtp_<command>``
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upon reception of a command line from the client. Built into the base
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:class:`SMTPChannel` class are methods for handling the following commands
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(and responding to them appropriately):
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======== ===================================================================
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Command Action taken
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======== ===================================================================
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HELO Accepts the greeting from the client and stores it in
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:attr:`seen_greeting`. Sets server to base command mode.
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EHLO Accepts the greeting from the client and stores it in
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:attr:`seen_greeting`. Sets server to extended command mode.
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NOOP Takes no action.
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QUIT Closes the connection cleanly.
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MAIL Accepts the "MAIL FROM:" syntax and stores the supplied address as
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:attr:`mailfrom`. In extended command mode, accepts the
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:rfc:`1870` SIZE attribute and responds appropriately based on the
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value of *data_size_limit*.
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RCPT Accepts the "RCPT TO:" syntax and stores the supplied addresses in
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the :attr:`rcpttos` list.
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RSET Resets the :attr:`mailfrom`, :attr:`rcpttos`, and
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:attr:`received_data`, but not the greeting.
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DATA Sets the internal state to :attr:`DATA` and stores remaining lines
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from the client in :attr:`received_data` until the terminator
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``"\r\n.\r\n"`` is received.
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HELP Returns minimal information on command syntax
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VRFY Returns code 252 (the server doesn't know if the address is valid)
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EXPN Reports that the command is not implemented.
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======== ===================================================================
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