what about log out and log in?
Mail app on windows 10 unlike windows 8 was always forced to use your Microsoft account mail, so you had to force yourself to live with it. but with windows 10 you can log out and in with any account.
You can try that if nothing appears, also you should see that the settings are correct since it will, by default, be about synching the last 2 weeks emails, so if you want to see really old emails there you have to change that setting.
But There is also the "cycling arrows" button that is used if you want to manually sync your mail. and then forcing the folders and everything to appear.