[Exim] Using Exim for Sending mail (SMTP Gateway)

Hello everyone,

I am wondering how to allow only the mail with a valid local-domain in the
"From:" field to be accepted in forward? I don't want my SMTP server to
become a SPAM-forwarder (even if I know spoofing is easy to do). We have
many different users on different ISP so an ip/host filtering is
impossible.

Thank you.

Simon Boulet