I am trying to add a manager to my YouTube brand account. She has a Google account with a btinternet.com email address (e.g. email@example.com) When I "invite" her to be a manager role of my YouTube brand account, YouTube changes her email address to firstname.lastname@example.org (and presumably sends the invitation to that email address). What is going on? I have invited other managers who don't have Gmail addresses with no problem.