The SMTP class¶
At the heart of this module is the
SMTP class. This class implements the
RFC 5321 Simple Mail Transport
Protocol. Often you won’t run an
SMTP instance directly, but instead will
use a controller instance to run the server in a subthread.
>>> from aiosmtpd.controller import Controller
SMTP class is itself a subclass of StreamReaderProtocol.
While behavior for common SMTP commands can be specified using handlers, more complex specializations such as adding custom SMTP commands
require subclassing the
For example, let’s say you wanted to add a new SMTP command called
All methods implementing
SMTP commands are prefixed with
must also be coroutines. Here’s how you could implement this use case:
>>> import asyncio >>> from aiosmtpd.smtp import SMTP as Server, syntax >>> class MyServer(Server): ... @syntax('PING [ignored]') ... async def smtp_PING(self, arg): ... await self.push('259 Pong')
Now let’s run this server in a controller:
>>> from aiosmtpd.handlers import Sink >>> class MyController(Controller): ... def factory(self): ... return MyServer(self.handler) >>> controller = MyController(Sink()) >>> controller.start()
We can now connect to this server with an
>>> from smtplib import SMTP as Client >>> client = Client(controller.hostname, controller.port)
Let’s ping the server. Since the
PING command isn’t an official
command, we have to use the lower level interface to talk to it.
>>> code, message = client.docmd('PING') >>> code 259 >>> message b'Pong'
Because we prefixed the
smtp_PING() method with the
decorator, the command shows up in the
>>> print(client.help().decode('utf-8')) Supported commands: DATA EHLO HELO HELP MAIL NOOP PING QUIT RCPT RSET VRFY
And we can get more detailed help on the new command.
>>> print(client.help('PING').decode('utf-8')) Syntax: PING [ignored]
These methods are deprecated. See handler hooks instead.
SMTP server class also implements some hooks which your subclass can
override to provide additional responses.
- This hook makes it possible for subclasses to return additional
EHLOresponses. This method, called asynchronously and taking no arguments, can do whatever it wants, including (most commonly) pushing new
250-<command>responses to the client. This hook is called just before the standard
250 HELPwhich ends the
EHLOresponse from the server.
- This hook makes it possible to return additional
RSETresponses. This method, called asynchronously and taking no arguments, is called just before the standard
250 OKwhich ends the
RSETresponse from the server.
SMTP(handler, *, data_size_limit=33554432, enable_SMTPUTF8=False, decode_data=False, hostname=None, tls_context=None, require_starttls=False, loop=None)¶
handler is an instance of a handler class.
data_size_limit is the limit in number of bytes that is accepted for client SMTP commands. It is returned to ESMTP clients in the
250-SIZEresponse. The default is 33554432.
enable_SMTPUTF8 is a flag that when True causes the ESMTP
SMTPUTF8option to be returned to the client, and allows for UTF-8 content to be accepted. The default is False.
decode_data is a flag that when True, attempts to decode byte content in the
DATAcommand, assigning the string value to the envelope’s
contentattribute. The default is False.
hostname is the string returned in the
220greeting response given to clients when they first connect to the server. If not given, the system’s fully-qualified domain name is used.
tls_context and require_starttls are related to the ESMTP
STARTTLScommand for secure connections to the server, based on RFC 3207. tls_context is used as the SSL protocol context, and there is no default. tls_context must be given and require_starttls must be True for
STARTTLSto be supported.
loop is the asyncio event loop to use. If not given,
asyncio.new_event_loop()is called to create the event loop.
The handler instance passed into the constructor.
The value of the data_size_limit argument passed into the constructor.
The value of the enable_SMTPUTF8 argument passed into the constructor.
220greeting hostname. This will either be the value of the hostname argument passed into the constructor, or the system’s fully qualified host name.
The value of the tls_context argument passed into the constructor.
True if both the tls_context argument to the constructor was given and the require_starttls flag was True.
The event loop being used. This will either be the given loop argument, or the new event loop that was created.
A method subclasses can override to return custom
A method subclasses can override to return custom
The method that subclasses and handlers should use to return statuses to SMTP clients. This is a coroutine. status can be a bytes object, but for convenience it is more likely to be a string. If it’s a string, it must be ASCII, unless enable_SMTPUTF8 is True in which case it will be encoded as UTF-8.
Coroutine methods implementing the SMTP protocol commands. For example,
smtp_HELO()implements the SMTP
HELOcommand. Subclasses can override these, or add new command methods to implement custom extensions to the SMTP protocol. arg is the rest of the SMTP command given by the client, or None if nothing but the command was given.