Spam is bad enough already. It already takes up loads of bandwidth traveling around the 'net.

This will just make it worse because of all the underliverables which will then bounce back.

Think of it... a spammer sends an email to a dud address. The mail server bounces it back to the spammer - who used a dud address. The returned mail message also bounces back. Maybe in a never-ending bounceback loop. Waisting bandwidth at the same time.

Michael Ross