I really wish there was a way to indicate, in DNS, that a domain never sends mail.
That way, if a mail server recieves mail claiming to be from that domain, it can be discarded out of hand.
I’ve got a bunch of domains that JUST do web serving … they never send mail. If the web server that they are hosted on does send mail, it’s sent from via the midrange.com mail server (and is identified as such).