:mod:`smtpd` --- SMTP Server
============================
.. module:: smtpd
:synopsis: A SMTP server implementation in Python.
:deprecated:
.. moduleauthor:: Barry Warsaw <barry@python.org>
.. sectionauthor:: Moshe Zadka <moshez@moshez.org>
**Source code:** :source:`Lib/smtpd.py`
--------------
This module offers several classes to implement SMTP (email) servers.
.. deprecated-removed:: 3.6 3.12
The :mod:`smtpd` module is deprecated
(see :pep:`PEP 594 <594#smtpd>` for details).
The `aiosmtpd <https://aiosmtpd.readthedocs.io/>`_ package is a recommended
replacement for this module. It is based on :mod:`asyncio` and provides a
more straightforward API.
Several server implementations are present; one is a generic
do-nothing implementation, which can be overridden, while the other two offer
specific mail-sending strategies.
Additionally the SMTPChannel may be extended to implement very specific
interaction behaviour with SMTP clients.
The code supports :RFC:`5321`, plus the :rfc:`1870` SIZE and :rfc:`6531`
SMTPUTF8 extensions.
.. include:: ../includes/wasm-notavail.rst
SMTPServer Objects
------------------
.. class:: SMTPServer(localaddr, remoteaddr, data_size_limit=33554432,\
map=None, enable_SMTPUTF8=False, decode_data=False)
Create a new :class:`SMTPServer` object, which binds to local address
*localaddr*. It will treat *remoteaddr* as an upstream SMTP relayer. Both
*localaddr* and *remoteaddr* should be a :ref:`(host, port) <host_port>`
tuple. The object inherits from :class:`asyncore.dispatcher`, and so will
insert itself into :mod:`asyncore`'s event loop on instantiation.
*data_size_limit* specifies the maximum number of bytes that will be
accepted in a ``DATA`` command. A value of ``None`` or ``0`` means no
limit.
*map* is the socket map to use for connections (an initially empty
dictionary is a suitable value). If not specified the :mod:`asyncore`
global socket map is used.
*enable_SMTPUTF8* determines whether the ``SMTPUTF8`` extension (as defined
in :RFC:`6531`) should be enabled. The default is ``False``.
When ``True``, ``SMTPUTF8`` is accepted as a parameter to the ``MAIL``
command and when present is passed to :meth:`process_message` in the
``kwargs['mail_options']`` list. *decode_data* and *enable_SMTPUTF8*
cannot be set to ``True`` at the same time.
*decode_data* specifies whether the data portion of the SMTP transaction
should be decoded using UTF-8. When *decode_data* is ``False`` (the
default), the server advertises the ``8BITMIME``
extension (:rfc:`6152`), accepts the ``BODY=8BITMIME`` parameter to
the ``MAIL`` command, and when present passes it to :meth:`process_message`
in the ``kwargs['mail_options']`` list. *decode_data* and *enable_SMTPUTF8*
cannot be set to ``True`` at the same time.
.. method:: process_message(peer, mailfrom, rcpttos, data, **kwargs)
Raise a :exc:`NotImplementedError` exception. Override this in subclasses to
do something useful with this message. Whatever was passed in the
constructor as *remoteaddr* will be available as the :attr:`_remoteaddr`
attribute. *peer* is the remote host's address, *mailfrom* is the envelope
originator, *rcpttos* are the envelope recipients and *data* is a string
containing the contents of the e-mail (which should be in :rfc:`5321`
format).
If the *decode_data* constructor keyword is set to ``True``, the *data*
argument will be a unicode string. If it is set to ``False``, it
will be a bytes object.
*kwargs* is a dictionary containing additional information. It is empty
if ``decode_data=True`` was given as an init argument, otherwise
it contains the following keys:
*mail_options*:
a list of all received parameters to the ``MAIL``
command (the elements are uppercase strings; example:
``['BODY=8BITMIME', 'SMTPUTF8']``).
*rcpt_options*:
same as *mail_options* but for the ``RCPT`` command.
Currently no ``RCPT TO`` options are supported, so for now
this will always be an empty list.
Implementations of ``process_message`` should use the ``**kwargs``
signature to accept arbitrary keyword arguments, since future feature
enhancements may add keys to the kwargs dictionary.
Return ``None`` to request a normal ``250 Ok`` response; otherwise
return the desired response string in :RFC:`5321` format.
.. attribute:: channel_class
Override this in subclasses to use a custom :class:`SMTPChannel` for
managing SMTP clients.
.. versionadded:: 3.4
The *map* constructor argument.
.. versionchanged:: 3.5
*localaddr* and *remoteaddr* may now contain IPv6 addresses.
.. versionadded:: 3.5
The *decode_data* and *enable_SMTPUTF8* constructor parameters, and the
*kwargs* parameter to :meth:`process_message` when *decode_data* is
``False``.
.. versionchanged:: 3.6
*decode_data* is now ``False`` by default.
DebuggingServer Objects
-----------------------
.. class:: DebuggingServer(localaddr, remoteaddr)
Create a new debugging server. Arguments are as per :class:`SMTPServer`.
Messages will be discarded, and printed on stdout.
PureProxy Objects
-----------------
.. class:: PureProxy(localaddr, remoteaddr)
Create a new pure proxy server. Arguments are as per :class:`SMTPServer`.
Everything will be relayed to *remoteaddr*. Note that running this has a good
chance to make you into an open relay, so please be careful.
SMTPChannel Objects
-------------------
.. class:: SMTPChannel(server, conn, addr, data_size_limit=33554432,\
map=None, enable_SMTPUTF8=False, decode_data=False)
Create a new :class:`SMTPChannel` object which manages the communication
between the server and a single SMTP client.
*conn* and *addr* are as per the instance variables described below.
*data_size_limit* specifies the maximum number of bytes that will be
accepted in a ``DATA`` command. A value of ``None`` or ``0`` means no
limit.
*enable_SMTPUTF8* determines whether the ``SMTPUTF8`` extension (as defined
in :RFC:`6531`) should be enabled. The default is ``False``.
*decode_data* and *enable_SMTPUTF8* cannot be set to ``True`` at the same
time.
A dictionary can be specified in *map* to avoid using a global socket map.
*decode_data* specifies whether the data portion of the SMTP transaction
should be decoded using UTF-8. The default is ``False``.
*decode_data* and *enable_SMTPUTF8* cannot be set to ``True`` at the same
time.
To use a custom SMTPChannel implementation you need to override the
:attr:`SMTPServer.channel_class` of your :class:`SMTPServer`.
.. versionchanged:: 3.5
The *decode_data* and *enable_SMTPUTF8* parameters were added.
.. versionchanged:: 3.6
*decode_data* is now ``False`` by default.
The :class:`SMTPChannel` has the following instance variables:
.. attribute:: smtp_server
Holds the :class:`SMTPServer` that spawned this channel.
.. attribute:: conn
Holds the socket object connecting to the client.
.. attribute:: addr
Holds the address of the client, the second value returned by
:func:`socket.accept <socket.socket.accept>`
.. attribute:: received_lines
Holds a list of the line strings (decoded using UTF-8) received from
the client. The lines have their ``"\r\n"`` line ending translated to
``"\n"``.
.. attribute:: smtp_state
Holds the current state of the channel. This will be either
:attr:`COMMAND` initially and then :attr:`DATA` after the client sends
a "DATA" line.
.. attribute:: seen_greeting
Holds a string containing the greeting sent by the client in its "HELO".
.. attribute:: mailfrom
Holds a string containing the address identified in the "MAIL FROM:" line
from the client.
.. attribute:: rcpttos
Holds a list of strings containing the addresses identified in the
"RCPT TO:" lines from the client.
.. attribute:: received_data
Holds a string containing all of the data sent by the client during the
DATA state, up to but not including the terminating ``"\r\n.\r\n"``.
.. attribute:: fqdn
Holds the fully qualified domain name of the server as returned by
:func:`socket.getfqdn`.
.. attribute:: peer
Holds the name of the client peer as returned by ``conn.getpeername()``
where ``conn`` is :attr:`conn`.
The :class:`SMTPChannel` operates by invoking methods named ``smtp_<command>``
upon reception of a command line from the client. Built into the base
:class:`SMTPChannel` class are methods for handling the following commands
(and responding to them appropriately):
======== ===================================================================
Command Action taken
======== ===================================================================
HELO Accepts the greeting from the client and stores it in
:attr:`seen_greeting`. Sets server to base command mode.
EHLO Accepts the greeting from the client and stores it in
:attr:`seen_greeting`. Sets server to extended command mode.
NOOP Takes no action.
QUIT Closes the connection cleanly.
MAIL Accepts the "MAIL FROM:" syntax and stores the supplied address as
:attr:`mailfrom`. In extended command mode, accepts the
:rfc:`1870` SIZE attribute and responds appropriately based on the
value of *data_size_limit*.
RCPT Accepts the "RCPT TO:" syntax and stores the supplied addresses in
the :attr:`rcpttos` list.
RSET Resets the :attr:`mailfrom`, :attr:`rcpttos`, and
:attr:`received_data`, but not the greeting.
DATA Sets the internal state to :attr:`DATA` and stores remaining lines
from the client in :attr:`received_data` until the terminator
``"\r\n.\r\n"`` is received.
HELP Returns minimal information on command syntax
VRFY Returns code 252 (the server doesn't know if the address is valid)
EXPN Reports that the command is not implemented.
======== ===================================================================
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