If you're going to be forced to use an email address as an ID, which I agree is poor practice, you'd definitely want it to be an operational one that is under y

If you're going to be forced to use an email address as an ID, which I agree is poor practice, you'd definitely want it to be an operational one that is under your control. Otherwise you're leaving an opening for someone else to come along later, set up that address, and take over your account.