I have added what I think they call login alias to my account. This blocks logins using the normal account username (which is my public email address), and only allows them via the alias (which is not public and just a random string). Not a single foreign login attempt since I enabled the alias.
You can enable it on account.microsoft.com > Account Info > Sign-in preferences > Add email > Add Alias and make it primary. Then click Change Sign-in Preferences, and only enable the alias.
You can enable it on account.microsoft.com > Account Info > Sign-in preferences > Add email > Add Alias and make it primary. Then click Change Sign-in Preferences, and only enable the alias.