What is the name for an apple iPhone email address?

I want to surprise my uncle with a facetime to his iPhone and I looked online and learned how to use facetime. I've tried his yahoo which ends with @yahoo.com but it didn't work so I want to figure out his iPhone email. I would ask him but it would ruin the surprise. What is apples email ending? @--- ?

An Apple email address may be.




But he could be using any email address - assuming he has signed up and activated FaceTime.