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:mod:`smtpd` --- SMTP Server
============================
.. module:: smtpd
:synopsis: A SMTP server implementation in Python.
.. 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.
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 extension.
SMTPServer Objects
------------------
.. class:: SMTPServer(localaddr, remoteaddr, data_size_limit=33554432)
Create a new :class:`SMTPServer` object, which binds to local address
*localaddr*. It will treat *remoteaddr* as an upstream SMTP relayer. It
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.
.. method:: process_message(peer, mailfrom, rcpttos, data)
Raise :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:`2822`
format).
.. attribute:: channel_class
Override this in subclasses to use a custom :class:`SMTPChannel` for
managing SMTP clients.
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.
MailmanProxy Objects
--------------------
.. class:: MailmanProxy(localaddr, remoteaddr)
Create a new pure proxy server. Arguments are as per :class:`SMTPServer`.
Everything will be relayed to *remoteaddr*, unless local mailman configurations
knows about an address, in which case it will be handled via mailman. 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)
Create a new :class:`SMTPChannel` object which manages the communication
between the server and a single SMTP client.
To use a custom SMTPChannel implementation you need to override the
:attr:`SMTPServer.channel_class` of your :class:`SMTPServer`.
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.
======== ===================================================================
|
