Unauthorized use of mail relays is already preventable. Why legislate
against something (which merely establishes a penalty for it) when you
can stop it from happening, cold. Just install qmail -- by default it
prevents relaying. http://www.qmail.org.[ For the sake of truth, I run that site, and I also provide
commercial support for qmail -- but I do both of those because qmail
helps stop spam. ]
So does sendmail.
But it doesn't have cute mailer-daemons and "hope things work out!" messages
like qmail.