It’s web only. Though, it does enforce app passwords. 

You can use an app password with Outlook once 2FA/MFA is enabled. These are issued to the user from Settings once they've enabled this requirement.

What is the use of an app password? 

Isn't my own password not good enough?

I've been asking around, but will outlook together with Smartermail support modern authentication? I guess it means: that outlook will also use MFA for verification on the smartermail server without the use of an app password?