Comment 4 for bug 1940603

@Todd, I somehow had missed you were already using the smtpd_sasl_tls_security_options config, sorry about that. I don't understand why telnet didn't display the 220 banner as the logs suggest it was sent:

  Aug 17 04:07:21 kangaroo postfix/smtpd[46495]: > kangaroo.unclet.net[127.0.0.1]: 220 kangaroo.unclet.net ESMTP Postfix (Ubuntu)

I doubt it will make a difference but maybe try with `nc -v 127.0.0.1 25` instead?

If would be nice if you could provide the output of `sudo ss -nltp`. Also, if you don't mind, please attach the main.cf and master.cf files so I can use them to reproduce here.