Old xbox account says it not connected to email

Thank you for contact us! I'm Anderson, an Independent Consultant and a Microsoft user like you.

good evening

If you're receiving promotions for your old Xbox account on the email that it should be connected to, it's possible that your old account is still associated with that email address.

To try to recover your old account, you can follow these steps:

Go to the Xbox account recovery page at https://account.microsoft.com/account/xboxlive.

Enter the email address or phone number associated with your old Xbox account and click "Next."

Follow the prompts to verify your identity. You may need to provide some personal information or answer security questions.

If the system is able to verify your identity, you'll be able to recover your old Xbox account and regain access to your saved games, achievements, and other account information.

On my xbox account these always write the old one and when I try to connect with the old one it says "it does not exist". I don't know the new email he put it so what should I do? Why are these so complicated? Can anyone help me?

in short old xbox live account lost, still want same Facebook on new account, can't access old xbox account to unlink, and Facebook doesn't show my Facebook as connected but when I try connecting Facebook to new account it says it's logged in to the old
account.

Thanks for the reply, I tried adding my new account to my old xbox account that but it says "This email is part of a reserved domain. Please enter a different email address."

the account connected to my old gamertag is a microsoft account, but it doesn't have @outlook or @hotmail) and the new email account that I want to be connected to my old gamertag is also a microsoft account but @gmail, not @outlook or @hotmail