Windows 10: Cannot remove accounts from the option used in another apps

I cannot remove an account from Settings / Email & Accounts / Manage. The delete button does not appear. When I click Manage, my browser opens and tells me to sign into an account in Microsoft Online. Both accounts that I want to remove are NO LONGER ACTIVE, so I don't have the option to log into those as one is a previous university account that has now been discontinued, and the other is from a previous job that I am not with the company anymore, and the email has also been discontinued. Furthermore, there is no option to remove those accounts, which is causing problems as things a

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Remove account

I suggest you backup your personalized files first before removing the account.
To delete an account, follow these steps:

1. Press WIN + X keys and click Command Prompt (Admin) from the menu.
2. Type the following command and press Enter. Replace test with the name of your sister's account. Code:

 

Cannot remove Mail app account

Hi,

For us to provide the appropriate troubleshooting step to resolve the issue, we'd like to ask for additional details. Please answer the following:

• Have you made any recent changes or installed updates before this issue occurred?
• Are you also getting an error message when trying to remove the email account?
• What troubleshooting steps have you tried so far?

For initial troubleshooting, we suggest running the Windows App Troubleshooter.

We look forward to your response.