Ubisoft wont unlink my xbox account from a account with a dead email, please help

For the past couple of weeks I have been emailing back and forth with Ubisoft Support, at first I was trying to find out what account is linked to my xbox account because I want my xbox account linked to the Ubisoft account that I use and it went back and forth a while and them not being helpful at all eventually they told me part of a email that aparently is connected with my xbox account, and they were incorrect it is a completely different email, and so I get in contact with the email provider and gave them the email and they basically said that it didnt exsist because they wanted to move away from those email address I guess and that one was deleted and I tell Ubisoft Support that and they still cant do anything aparently because I cant prove the ownership of a Ubisoft account because I cant get into a email that dosent exsist anymore and they refuse to tell me how I can prove the ownership of the xbox account that I am trying to unlink from the bascially dead Ubisoft account. Is there a way that I or microsoft support can unlink my xbox account from the again basically dead Ubisoft account

:)