[Exim] mysql help

This is a multi-part message in MIME format.
--
[ Picked text/plain from multipart/alternative ]
ok i have a bit of a problem

im trying to use mysql as a backend for email users, now, this is what i have working.....

local domains are grabbed from mysql.

now what i want is for exim to check the user exists in the db, and not on the system

the database structure:

Table name: email_addresses
|--- username
|--- password
|--- domain

so how would i check the user exists in the db?

currently its checking the server users:

localuser:
driver = accept
check_local_user
transport = local_delivery
cannot_route_message = Unknown user

im not sure how to do this, its gotta chack the user exists, BUT, also, at the same time, check that the user exists for the domain the the email is being sent to

for example, on the server might be a user: matt

matt may exist for example.com but not for example2.com

so i want mail to matt@??? to be accepted but not to matt@???.

in the email_addresses table the username and the domain are stored for each user so that check is possible but how?

could anyone give me an example?

thanx in advance

Matt.
--