How to remove someone from the Global Exclude list?

I have a customer who is in the Global Exclude list.  He is complaining that he isn't receiving our emails -- including confirmation emails after he has registered for an event.

1. How can I see WHY someone is in the Global Exclude list?
2. How can I remove the person from Global Exclude -- in this case on the individual's request?

I'm in E10.

Thanks for the advice!