[Logician]

If I'm not wrong, easy (sometimes only) way to do this is to have the control of your mail server (dedicated mail server). Then when a mail bounce you can make your mail server trigger a script which will do what you requested.

But most of the times (with regular hosting) you wont have the control of your mail server, thus cant do this. But there may be a workaround: Ask your host where you incoming mails reside in the server and if your scripts can have access to that folder. If yes, you can write a script which will periodically check your incoming folder and look for bounceback mails, if catch, it will relate with the db of you email address' and remove the relevant address from the database. This is the hard way..

Regards,