I want to change the primary alias of my microsoft account to a new email and I'm not sure...

Hello ChloéThery,

Thank you for posting on the Xbox forums. We understand that you are interested in

changing your primary alias. If you are receiving that error message, it means the email address you want to use is already the primary alias of a Microsoft account. You must first log in to that account. If you need help

resetting the password, you can use our support article. Once you have logged in to that account, you can change the primary alias for it. After you have set up a new primary alias on that account, you can remove the email that you want from it. At that
point, you can go ahead and use that email address as the primary alias of your main account. Be sure to let us know the results!

I changed the email on my gamer tag by signing in to microsoft live account, creating a new alias and assigning it as the primary account, then deleting the old alias.

Hello pirostheo game,

Thank you for keeping us updated. There is a way to manage the email addresses of each Microsoft account. You must first remove the email that you want to use as

the primary alias. Once the primary alias on the Microsoft account has been changed, you can use the email address that you want on a different Microsoft account. The main reason you have to take this step is because you cannot have the same primary alias
for two different Microsoft accounts. It's basically just moving an email address from one Microsoft account to another. The article we provided contains steps on how to change the primary alias. You must do these steps for both accounts. Be sure to let us
know the results!

I'm not entirely sure if this is possible to do. You might be able to add a new alias (Alias B) to your account and make that new alias the primary account (Alias A). Then create another email address(Alias C) and add your current email (Alias A) as a primary
alias to that account

But since you can't transfer data from one account to another I'm guessing it's not something that's possible

You can find more information regarding what I'm talking about here:
https://beta.support.xbox.com/help/Account-Profile/manage-account/change-email-sign-in-for-microsoft-account

[i][b]Warning[/b] When removing an email alias that’s a Microsoft domain (such as @Outlook.com, @Live.com, or @Hotmail.com), that email is completely deleted from our systems and can no
 longer be used to send or receive emails. It won’t be available for use again as an alias on another account. Microsoft does not recycle email addresses, so it may not be reclaimed at a future time.
[/i]

So, If I'm understanding your question, you have a gamertag tied your dad's email address that you want to tie to your email address instead, right?

In theory, as long as you have access to both accounts, you should be able to change the associated email addresses(s). You'll need to login to your old Microsoft account (dads) and change the primary email alias to the new email address you want to use.
Before you can do that, you will need to login to your new account (with the email you want to use) and change the primary email alias to some other email account you have. Then, have your dad login to his account and change the primary email alias to the
email you want to use instead. He would be forfeiting his account to you, but that is the only way to keep the old gamertag with your new email address. Keep in mind, if he is the primary account over a family of Microsoft accounts, this would transfer everything
to you... in theory.