Problem with changing Apple ID for email
I will shortly lose my current email address so need to change my Apple ID. My other email address was a back-up address and when I try to use it as my ID address it tells me I can't - even though I have now deleted it as a back-up.
I see that others have reported a similar problem over a number of years now, and wonder if there is a solution?
MacBook Air 11″, macOS 10.14