A Microsoft file hosting and synchronization service.
It happened to other members of my team on the 3rd of March and now the rest of my team this morning. Not having access to this functionality is a real disaster, we will have to change our whole way of working or migrate to a different product. Does anyone have any recommendations for alternatives, bearing in mind that we need a solution where multiple users can work on the same document at the same time as well as being able to work out of windows explorer and not on the web?