[exim] Require authentication from local users

Hi everyone:

I'm hot in pursuit of my time-limited ACL. I've run into yet another
stumbling block; my exim config allows local users to send mail without
authentication.

Can I get a couple of hints on how to configure exim to:

1. Allow unlimited receipt of emails for the local domains
2. Require local users to authenticate at all times
3. Prevent open relaying

Obviously I'm concerned about inadvertently causing 3. 1 and 2 are
somewhat contradictory as I would like to authenticate all local users,
even if they're sending local email.

(My "problem" is that exim is so bloody stable that I never have to touch
it, so when I want to change the config I basically start over - having
forgotten everything I've learned before... The last time I had to
reconfigure it was in 2007.)

--Yan

--
Yan Seiner, PE