Server is running sendmail 8.14
From any machine:
$ telnet mydomain.com 25 HELO mydomain.com MAIL FROM: <firstname.lastname@example.org> RCPT TO: <email@example.com> DATA this is spam .
How do I require authentication for any mail that claims to be from a local domain?
This seems like a no-brainer anti-spam feature.
FROM TO RESULT any non-local "Relaying denied. Proper authentication required." non-local local success  local local success 
 This is acceptable. Outsiders can send to local users without any kind of authentication. Various DNS checks can be done.
 This is the problem. Why should I allow anyone to mail a local user while claiming to be a local user?