[Exim] Returnd mail / undeliverable mail

People I have a webhosting company and some of my clients are using a
PHP/PERL based maillist. And when the email can't be delivered all
mail is returned to the servers domainname.

This is annoying because I, the administrator get all the undelivered
mail on my account.

How do I configure exim so that email is returned to the from adress
and not to the: user on which Apache is running on.

Sincerly,

N. Elsten