apple id
How do I sign out of icloud when I no longer have that e mail address?
iPhone 6
As long as you know the Apple (iCloud) password that goes with that address, you should be able to sign out. The e-mail address does need to be active to sign out. After signing out, consider doing a name change.
What to do after you change your Apple ID or password - Apple Support I suggest doing this before you change your Apple ID or password.