[Exim] help with routers

This is a multi-part message in MIME format.
--
[ Picked text/plain from multipart/alternative ]
ok i want to use mysql to hold the email address, password and maildir of each user in a table called accounts, and also domains in a table called domains

now my question is, if i have the email address of the user in a contant called USER_EMAIL_ADDRESS, the password (which is md5) in a constant called USER_PASSWORD and the mail dir in the constant called USER_MAIL_DIR

how would the router config look to save incomming mails to the users in mysql to their home dir. and if the mysql user dont exist, send an email back saying unknown user

note: i dont want any email what so ever to go to local system users.

also how would the user authentication look for mysql users sending mail from my server, how would i do that?

i have looked through them exim docs loads of times, but i dont understand.

i found the router than checks if a local user exists, it runs: check_local_user but how do u check a mysql user

exim is built with mysql support so if anyone could help me with the receiving mail router and sending mail using authentication then i would be very greatful

thanx, matt.
--