[kh99]

Well, emails are sent by calling the "vbmail" function, and that function has parameters for specifying the From address as well as additional headers. So you should be able to do what you want by finding the right calls to vbmail() and changing the parameters. I would figure it out for you but I don't have the time to work it all out right now. I might be able to do it later if no one else has figured it out by then.

Edit: now that I think about it a little more, I'm guessing a plugin using hook mail_send could adjust the fields as necessary so that you wouldn't have to edit any files.