[net.mail.headers] Domain names

Murray.pa@XEROX.ARPA (05/22/85)

As long as we are screaming about bogus names, I'll remind everybody
that there are lots and lots of systems out there that still think their
name is foo rather than foo.ARPA.

Anybody fixing their code to use domain names had better include some
hackery to default things to .ARPA if nothing better makes sense.