Feb. 9, 2026
5:14 p.m.
Dennis
Post the log entries related to one such message, from both Postfix *and* Mailman, especially those related to debugging.
We cannot help you interpret what you don't show us.
It doesn't help us when you tell us what is "supposed to happen" without explaining why you think that is what the documentation and configuration say that Postfix and Mailman are supposed to do. Note that *both* Mailman and Postfix may have some influence on the credentials of the sender presented to remote recipients.
-- GNU Mailman consultant (installation, migration, customization) Sirius Open Source https://www.siriusopensource.com/ Software systems consulting in Europe, North America, and Japan