There are all sorts of reasons that you could lose files. They could be deleted or overwritten by accident, be in a previous employee's inbox that's been deleted, or even lost because they were encrypted in a ransomware attack (see our last blog for more about that). In fact, the No. 1 cause of data loss in systems such as Microsoft Office 365 is accidental deletion. About 70 per cent of all lost data is due to end-users accidentally or maliciously deleting data.