exactly! I always am worried about somebody sending out emails with my domain appearing as the sender, and then getting shut down because of complaints.
And all the while I would never have even known about the problem until it was too late.
That happened to me just recently when someone hacked into my server and used one of the domains for phishing. Eventually the server was shut down because of zillions of bounces and complaints.
I had to start from scratch with a blank server, getting everything installed again….