We’re working on the ability to share a file or folder with a specific Microsoft Account.John McHugh commented
Part of the issue here is that there is a requirement for both secure and public access to the files. There should be a way to provide access to select persons who need to login to get to the files and also a way to provide a more unsecure public access to files with just a link. Currently we have a mishmash of sharing with the link being unsecure and the email share being any one with a Microsoft login. I have been trying to find out why the inconsistency and why it was changed recently to be inconsistent. I share out pictures using the link function and don't understand why all of sudden the email version requires a login.