This is completely off topic from this thread, but one way to easily cut down on spam (that would break many email senders today) would be to require that a mai

This is completely off topic from this thread, but one way to easily cut down on spam (that would break many email senders today) would be to require that a mail server can only send email for a domain you own. Yes, I'm familiar with DKIM and similar tools, but they don't go far enough.