Prevent bounce back of PHP mail to server

I have CWPPro with the latest update.
I can see at /var/spool/mail there are many email bounce because of PHP mail script. If PHP mail send the email and that email address does not exist, it will bounce back to usercwp@hostname, for example: gtk08@abc.domain.com, where abc.domain.com is the server's hostname.

How to prevent it and send that bounce email to the email of account's owner? When creating a new account in CWP, we put the customer email address. So, how to forward that bounce email to onwer's email?

Thanks.