Notify agent if requester email is bounced or rejected

So, I'm surprised I never thought of this until now, but it seems like an oversight to me. Maybe I'm missing something? Here's the scenario:

We have an environment where tickets are created using the API from a contact form on our site where the user enters their email address.

When an agent responds to the ticket, what if the email address the requester entered is wrong? If the message is rejected or bounced, the agent would never know! They would go on thinking this person is ignoring them and not have any sort of idea that the requester never got the message.

Can we add some way for Zendesk to notify the agent that the reply was not received? Would be pretty nifty.

Thanks!