[exim] Redirect/Rewrite Problem

Hi!

I've got a problem configuring exim4 on debian sarge:

The host recieves email which was previously captured for a domain and
forwarded to a single email address:

so paul@??? and peter@??? get forwarded to
post@???

AFAIK just the envelope is affected by this forward. Now the
receiving host has to expand the original recipient addresses
(@mydomain.com) and deliver the mail localy. Mail to non-existent
users should be bounced to the original sender.

Any idea how to do that?

Thanks

Martin