A couple of days ago, a customer sent a mail that didn't get to the intended recipient because it was blocked by the mail server due to size restrictions.
Let's just say there was a lot of trouble raised.

Anyway, my superiors want to setup a notification service that would send a mail to the sender when the mail cannot be sent with reason and would also send a mail to the intended recipient that someone tried to send him/her a mail but couldn't because ....

You get the picture?

I am in need of assistance as to how to achieve this.

Any ideas?