User for emails scripts return path

Well, ideally the return-path should be the From: header not To:. However, exim is setting as required by the RFC's where the return-path should be username@hostname. If you're not running phpsuexec, your php scripts are running under the nobody user and so they're correctly being given a return-path of nobody@hostname. If you want to change that behaviourm then you either need to use phpsuexec so that php scripts run under the username of the virtualhost or use the exim mod that rewrites email headers which I recently pointed out in the thread regarding AOL email bounces.