[exim] Authenticating SMTP connections agains MySQL database…

I currently have all my accounts setup to authenticate via a MySQL
database that stores the local part, domain name and passwords stored as
a SSH1 hash. When checking email this works just fine, but I can't
figure out how to get my users authenticated when they are trying to
send email.

I don't want to have anything setup for relaying emails but currently
whenever I try to send email I get the relay not allowed error message.
This is a home server that I have multiple domains on and have
connections for the outbound emails coming from multiple locations.
(Home, work, mobile, kids away at various locations) Is it possible to
have each user authenticate to the MySQL database prior to sending the
email and denying the rest of attempts if they user isn't in the database?

Thanks,
-Eric