[Exim] Error messages and system users.

Since a few months I'm running PHP as the owner of the PHP files. The
advantage of this is, that when "user1" sends out a message I can
(back)track it. The disadvatage is however that bounces and error
messages are sent to:

system_user@system_host_name

And I want to return those to the orginal sender. I know you can user
the option trusted_users but this is to compicated for a webserver.
Therefore I was wondering if it is possible to rewrite certain
adresses based on a text file, containing all local system users and
the domains matched with it.
Is this possible if so how or am I lookingover a certain function.

Thanx,


N. Elsten