Hi, I'm John! I will help you with this.
You cannot close or delete a Microsoft/Outlook account if you no longer have access to it. Only someone who can successfully sign in to the account can request its closure.
If you’re referring to removing that email account from your PC, phone, or apps so it’s no longer accessible on your devices, please let me know and I can guide you through the steps.
Click "Add comment" to let me know.
Regards,
John J.D.