Update email adress for my gamertag

Yes but the target email is already exist, It doesn't work in this case.

Regards,

Yes but the target email is already exist, It doesn't work in this case.

Regards,

You will not be able to use an email that is already a Microsoft Account.

See this page: https://support.xbox.com/my-account/microsoft-account/change-email-sign-in-for-microsoft-accou...

So by making a third email adress I can link the unwanted gamertag with the new adress, and then i can link both my two older email adresses to the desired gamertag?

If the "Forgot Microsoft Account Solution" does not help, try going through all your emails that you own and try to sign in on
https://account.microsoft.com.

When you try to sign in, do NOT create a new account if the page asks you to do so.

If you still can't find the Microsoft Account email for your Gamertag, you would have to contact the official support via
https://support.xbox.com/contact-us, but be aware since malicious users have tried to get access to other people's Microsoft Accounts by social engineering support agents, they
have to make sure that you really are the owner of the account.

So it would help, if you had added as much personal information to your account as possible like your correct date of birth, your home address, your phone number(s) and your payment details like bank account, credit card or the likes.

If you didn't have those information added to your account, I'm afraid there is not much that can be done in that case.