Microsoft will display ‘unverified’ to your users next to your app name during the OAuth flow. Obviously, this is not ideal. It erodes people’s confidence and will prevent some of them from completing the sharing request.
To fix it, you’ll need to become a verified member of the
Microsoft Partner Network (MPN). This process is not complicated. Microsoft will verify some details about your business and issue you a Publisher ID. You can then add it to your App Registration to enable the permission prompt, including a verified badge.