Wolfgang Bock via Mailman-users writes:
I tested port 25 with swaks ->mail to user on server: localhost port 25 -> everything fine
What is "swaks"?
Apr 07 12:09:21 2020 (28206) Cannot connect to SMTP server localhost on port 25
Is it possible that Postfix is configured for TLS connections only? If so, it is probably listening on port 465 (the "submissions" port, AKA ssmtp and smtps) or (less likely) 587 (the "submission" port -- no trailing "s"). Mailman needs to be configured correctly for this. See
https://mailman.readthedocs.io/en/latest/src/mailman/mta/docs/connection.htm...
It's barely possible that Postfix is listening on port 25 but insists on TLS. But that's very unusual, and I think that would produce a SMTP error such as "Need STARTTLS" or "Need SASL" (which happen *after* the TCP connection is established) instead of "Cannot connect" (which suggests a TCP error before a connection is completed).
I have no idea what to do for solving my problems.
That's when we're most of service. At least, I hope so! :-)
Steve