E-mail for PS5 and PS4.

[Wallace1297]

Do the e-mail addresses for the PS5 and the PS4 prior to transfer have to be the same address ? Because when I try to change the e-mail address of the PS4 to match the PS5 (or vice-versa) I always get a message which reads 'Cannot sign in using another player's sign-in ID'. That leads me to believe that the e-mail's can't be the same and if it can be the same then what is that message all about ?