I have an old Exchange account, I don't have access to it nor remember the password.
I want to delete it.
When I go to Internet Accounts, select it, and click "-" to delete it, it asks "are you sure", I say "yes", and nothing happens. The account is still there.
Best Answer
If it was installed using a Profile sometimes you cant remove it using Internet Accounts. Instead you need to go to System Preferences -> Profiles and remove the email profile.