we have a somewhat unique situation (from upper management). We will have a small subset of staff who will be working with us but they are not part of our company. They will be a separate business but we will provide IT support. We will set up their public domain and get them O365 (which will includes SharePoint/One drive removing the need for any files servers). The only issue I have is authentication, the staff will be working remotely, would azure ad join make sense here? By default SharePoint/One drive already requires you to log in before you can do anything. I'm failing to see what Azure AD join will bring to the table.