[Exim] Returned mail

How come that when a user send's a email and when it isn't able to
deliver it I get the error message and not the user who is sending
the email??

Apache runs as user httpd. So PHP also use that uid. And all
undeliveral email is returned to httpd@???. Really
frustrating. How can I solve this??

Thanx in advance

(Yes I searched the user digest, but coul'n't find it :()

N. Elsten