I run against a problem for which I not yet found a solution

I manage the general email address of the school. An email comes for mr XXX. I forward the email to mr XXX. The email gets as the sender the general email address of the school. Mr. XXX answers this email and is sent to the general email address instead of de original sender of the email. How do I manage that such a message holds the original sender?

With PegasusMail (I use that temporarily again now to forward this email) it is possible to forward without editing, but I want to be able to do this in Groupwise 8. Anyone who knows how? We enabled flat forward in the GWIA and it works in combination with rules. Is it possible from single emails?