iMessage - New Apple ID question

Hi everyone,

I want to clear out my iMessage app and start afresh so to speak. I plan on changing my Apple ID to a new email.

However, I'm just wondering, once I update the email and start using iMessage what will happen if someone tries to contact me through iMessage using my old email.

Do they get a notification alerting them that I've updated my email, does the message just bounce back as undeliverable or would it just look like it sent and they know no different?

Thanks for any insight. I'm using iMessage on an iPod by the way.