Hey there! Nice to meet you!
If you can access the email account, you can manually close it by clicking the option "close account" through this link, then follow the instructions:
However, if you can no longer access the account, the only way to close it is to wait for it to be deleted due to inactivity.
As stated by Microsoft, accounts that have not been signed in or have been locked for more than 2 years will be deleted due to inactivity, and they can no longer be recovered: https://support.microsoft.com/topic/microsoft-account-activity-policy-7c0a9fa7-0982-b7c6-fd72-df852b63699f
Thank you for your understanding.
Best regards,
Darhyl