I have a mail account in Mail that I want to delete but it's not possible since that account is not present in the System Preferences Internet Accounts. Any idea how to deal with this? Seems to me that either the System Pref config file is corrupted or maybe the Mail.app. config file. I've tried to add an account to the System Preferences Internet Accounts with the same data as the one that only shows up in Mail but when doing that no new account is added to System Preferences.