• Bugfix: ‘Future exception was never retrieved’ warning in SMTPProtocol after successful connection close and garbage collection.

  • Cleanup: Updated FlowControlMixin logic from stdlib


  • BREAKING: Drop Python 3.7 support.

  • BREAKING: Positional arguments are now positional only, and keyword arguments are keyword only.

  • BREAKING: Passing source_address as a string argument (deprecated in 2.0) is now an error. source_address takes a (addr, port) tuple that is used as the local_addr param of asyncio.create_connection, allowing for binding to a specific IP. The local_hostname argument takes the value to be sent to the server with the EHLO/HELO message (which is what source_address was used for prior to 2.0).

  • Change: don’t use timeout value passed to connect everywhere, only for the initial connection (credit @wombatonfire)

  • Change: removed unnecessary connection lost callback

  • Change: revised handling for ‘Future exception was never retrieved’ warnings in protocol


  • Bugfix: don’t send extra EHLO/HELO before QUIT (credit @ikrivosheev)

  • Change: added SMTPConnectionResponseError for invalid response on connect only (credit @ikrivosheev)


  • Bugfix: “tests” and “docs” in the sdist should be includes, not packages, so that they do not get put in site-packages.


  • BREAKING: Drop Python 3.5 and 3.6 support.

  • BREAKING: On connect, if the server supports STARTTLS, automatically try to upgrade the connection. STARTTLS after connect can be turned on or off explicitly by passing start_tls=True or start_tls=False respectively.

  • BREAKING: Remove deprecated loop keyword argument for the SMTP class.

  • Change: The source_address argument now takes a (addr, port) tuple that is passed as the local_addr param to asyncio.create_connection, allowing for binding to a specific IP. The new local_hostname argument that takes the value to be sent to the server with the EHLO/HELO message. This behaviour more closely matches smtplib.

    In order to not break existing usage, passing a string instead of a tuple to source_address will give a DeprecationWarning, and use the value as it if had been passed for local_hostname.

    Thanks @rafaelrds and @davidmcnabnz for raising and contributing work on this issue.

  • Bugfix: the mail_options and rcpt_options arguments to the send coroutine no longer cause errors

  • Cleanup: Refactored SMTP parent classes to remove complex inheritance structure.

  • Cleanup: Switched to for sync client methods.

  • Cleanup: Don’t use private email.message.Message policy attribute (instead, set an appropriate policy based on message class)


  • Security: Fix a possible injection vulnerability (a variant of

    Note that in order to exploit this vulnerability in aiosmtplib, the attacker would need control of the hostname or source_address parameters. Thanks Sam Sanoop @ Snyk for bringing this to my attention.

  • Bugfix: include CHANGLOG in sdist release

  • Type hints: fix type hints for async context exit (credit @JelleZijlstra)


  • Bugfix: fix authenticated test failures (credit @P-EB)


  • Bugfix: avoid raising asyncio.CancelledError on connection lost

  • Bugfix: allow UTF-8 chars in usernames and password strings

  • Feature: allow bytes type args for login usernames and passwords


  • Bugfix: parsing comma separated addresses in to header (credit @gjcarneiro)

  • Feature: add py.typed file (PEP 561, credit @retnikt)


  • Feature: add pause and resume writing methods to SMTPProcotol, via asyncio.streams.FlowControlMixin (thanks @ikrivosheev).

  • Bugfix: allow an empty sender (credit @ikrivosheev)

  • Cleanup: more useful error message when login called without TLS


  • Bugfix: removed docs and tests from wheel, they should only be in the source distribution.


  • Bugfix: Fix handling of sending legacy email API (Message) objects.

  • Bugfix: Fix SMTPNotSupported error with UTF8 sender/recipient names on servers that don’t support SMTPUTF8.


  • Feature: Added send coroutine api.

  • Feature: Added SMTPUTF8 support for UTF8 chars in addresses.

  • Feature: Added connected socket and Unix socket path connection options.

  • Feature: Wait until the connect coroutine is awaited to get the event loop. Passing an explicit event loop via the loop keyword argument is deprecated and will be removed in version 2.0.

  • Cleanup: Set context for timeout and connection exceptions properly.

  • Cleanup: Use built in start_tls method on Python 3.7+.

  • Cleanup: Timeout correctly if TLS handshake takes too long on Python 3.7+.

  • Cleanup: Updated SMTPProcotol class and removed StreamReader/StreamWriter usage to remove deprecation warnings in 3.8.

  • Bugfix: EHLO/HELO if required before any command, not just when using higher level commands.

  • Cleanup: Replaced asserts in functions with more useful errors (e.g. RuntimeError).

  • Cleanup: More useful error messages for timeouts (thanks ikrivosheev!), including two new exception classes, SMTPConnectTimeoutError and SMTPReadTimeoutError


  • Bugfix: Set default timeout to 60 seconds as per documentation (previously it was unlimited).


  • Bugfix: Connection is now closed if an error response is received immediately after connecting.


  • Bugfix: Badly encoded server response messages are now decoded to utf-8, with error chars escaped.

  • Cleanup: Removed handling for exceptions not raised by asyncio (in SMTPProtocol._readline)


  • Bugfix: Removed buggy close connection on __del__

  • Bugfix: Fixed old style auth method parsing in ESMTP response.

  • Bugfix: Cleanup transport on exception in connect method.

  • Cleanup: Simplified SMTPProtocol.connection_made, __main__


  • Bugfix: Close connection lock on on SMTPServerDisconnected

  • Feature: Added cert_bundle argument to connection init, connect and starttls methods

  • Bugfix: Disconnected clients would raise SMTPResponseException: (-1 …) instead of SMTPServerDisconnected


  • Bugfix: Commands were getting out of order when using the client as a context manager within a task

  • Bugfix: multiple tasks calling connect would get confused

  • Bugfix: EHLO/HELO responses were being saved even after disconnect

  • Bugfix: RuntimeError on client cleanup if event loop was closed

  • Bugfix: CRAM-MD5 auth was not working

  • Bugfix: AttributeError on STARTTLS under uvloop


Initial feature complete release with stable API; future changes will be documented here.