phpBB adds the email address listed in the from and reply-to, so unless you already modded some email functionality, you should be getting bounces. The question would be if you see you admin address in the from address of the board.
Also, this may be moved to phpBB Support due to this not being a MOD Request anymore.
LifeIsPain - one who needs to be smackedLife is pain, highness! Anyone who says differently is selling something.