Managing personal Outlook.com account settings, security, and privacy
Tbh, the new outlook is lousy and problematic. I am facing the same issue where i couldn't remove/delete the "suggested account" data which have all the passwords saved somewhere.
The issue I am facing is i changed one of my email account password and this "New Outlook" app have no option to update the password or repair the email syncing. It just keeps on asking me to press Sign in to "fix" or Manage Account but all it shows is just error. There is no way to fix it, even after searching for all the outlook files and deleted them also no use.
I switched back to the old Mail & Calendar app and I can fix the account syncing simply by just keying in the new password when the app prompted me.
I hope Microsoft doesn't kill the great Mail app to replace with a junk "New Outlook" app that gives trouble more than the old reliable app.