In the /var/log/mailman3/smtp.log I have at the same time:
Jan 01 10:54:37 2022 (126980) Available AUTH mechanisms: LOGIN(builtin) PLAIN(builtin) Jan 01 10:54:37 2022 (126980) Peer: ('127.0.0.1', 54816) Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) handling connection Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) Data: b'LHLO yyy.hu' Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) Data: b'MAIL FROM:<horvath.arpad.szfvar.nospam@gmail.com>' Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) sender: horvath.arpad.szfvar.nospam@gmail.com Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) Data: b'RCPT TO:<test@lists.xxx.hu>' Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) recip: test@lists.xxx.hu Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) Data: b'DATA' Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) Data: b'QUIT' Jan 01 10:54:37 2022 (126980) ('127.0.0.1', 54816) connection lost Jan 01 10:54:37 2022 (126980) Connection lost during _handle_client()
I have these package versions
ii python3-urllib3 1.26.5-1~exp1 all HTTP library with thread-safe connection pooling for Python3 ii python3-requests 2.25.1+dfsg-2 all elegant and simple HTTP library for Python3, built for human beings ii python3-requests-oauthlib 1.0.0-1.1 all module providing OAuthlib auth support for requests (Python 3) ii python3-requests-toolbelt 0.9.1-1 all Utility belt for advanced users of python3-requests