When I got my iPad and then MacBook Air I was still an android and windows user, so I used a gmail address for my Apple account. Eventually I used a custom domain and switched the account email address.

I am currently trying to wipe my MacBook to give to my daughter for college. But it needs me to sign out of find my and it has the original gmail address. It is not accepting the password, and when I do to find my nothing is signed in. Any tips? The only thing a search turns up is how to sign out nothing about it being a defunct account name.