[Exim] replacing sender by from header?

hello,

on our web server are a lot of virtual domains sending mail through
php or perl scripts. in certain cases these messages bounce and come
back to the postmaster account.

is there a way of replacing the sender address (currently for all
domains www-data) by the from header which in most cases has been set
by the webuser to his email address? we want these bounces to go to
the user sending them instead of being sent to the user www-data
ending at postmaster.

has anybody dealt with this kind of situation?

--
jens-ingo

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