Your TTU account is listed in Windows under Settings > Accounts > Email & app accounts. You would like to delete it. However, if you click the "Manage" button you are taken to the eRaider sign-in page. You're unable to sign in because your eRaider and TechMail account is either disabled or deleted.

You need to disconnect your TTU account in Windows first.

1) Open Settings.

2) In the left-hand menu, click Accounts.

3) Click Access work or school.

4) Click once on your TTU account.

5) Click Disconnect.

Outcome

Your TTU account has been removed.