[exim] Exim rewriting question

Hi,

I've got an "address rewriting" problem with exim4. Maybe someone got an
idea on how that can be solved.
I need to rewrite a recipient address (source@???) to multiple
target addresses (1@???, 2@??? etc...)

The e-mail is later delivered to a third party software whitch actually
needs the target addresses in the To: field or the further processing
of the mail will fail. (Software sadly cannot use the envelope or any
other header field.).

What i tried so far:

1. Using a redirect router: The e-mail gets redirected correctly, but
"To:" field is not rewritten, whitch in my case as explained above.
2. Using a rewrite in the "rewrite section" of the configuration:

source@??? 1@???,2@??? Tt

I would be very grateful for any hint, that could help me in this matter.

with best regards

Christian Hofstede