Managing personal Outlook.com account settings, security, and privacy
Hello, thank you for reaching out to Microsoft Q&A.
Here is what may have happened:
The hacker appears to have gained access to your Microsoft account, deleted your @Outlook.com email alias, and added their own email address to the account.
When this happens, you cannot recreate the same username (email address), and that address cannot be associated with any other Microsoft account again. It is a permanent deletion of the email address, and it cannot be recovered.
So, to avoid this situation happening in the future, make sure you secure your active Microsoft accounts with a Strong password and enable two-factor authentication for added security.
How to help keep your Microsoft account secure
If you have purchased any games or apps from the Microsoft Store, you can use the Xbox account recovery form to submit an account recovery request and see if the team can help recover your account.