[exim] emails split with multiple recipients

Hi all,

Q0807: I want to rewrite local sender addresses depending on the domain of
the recipient.

A0807: In general, this is not possible, because a message may have more
than one recipient and Exim keeps just a single copy of each message. It may
also deliver one copy of a message with several recipient addresses. You can
do an incomplete job by using a regular expression match in a rewrite rule
to test, for example, the contents of the To: header. This would work except
in cases of multiple recipients.

I have a rewrite rule that modifies all incoming senders but if the
recipient exists in a supplied text file (whitelist) it should leave the
sender intact. Only when there are multiple recipients and one of them is in
the whitelist and others are not it doesn't really do what I'm after.

Any suggestions anyone?

Thank you
-src-