I have the exact same problem with ubuntu 22.04.2 and latest Virtualmin 7.5 and Webmin 2.021.
See … Some e-mails bounced with unknown user but are forwarded
The filter option in Usermin works as a workaround. Thank you for that.
Also if you add a forwarder in usermin ‘mail forwarding and Replies’ ->’ Forward to another address’ → Yes, forward to my@gmail.com. The mail is not delivered and not forwarded, sender gets a message from MAILER-DAEMON that the message could not be delivered with the reason ’ too many hops’
Not normal behavior i guess ?