The Open File Backup Unlimited add-on protects Windows files (on NTFS file systems) that are open and in use. It protects files on multiple volumes as well as business-critical server applications that run 24 hours a day including e-mail, database, CRM, accounting, or proprietary applications. For desktop and notebook computers, backups can take place while e-mail applications and other applications are in use. A single Open File Backup Unlimited add-on license protects the Retrospect backup server and all networked client computers.