OST file is the offline storage file of the Exchange server. It may become unusable due to Exchange server crash, mailbox deletion or user account deletion from Active from Active Directory. In such situations, where OST file becomes unusable, using OST file tool can help the user to access its email data with MS Outlook by performing OST to PST conversion. OST file tool recover all available email items including mail messages, folders, posts, appointments, contacts, tasks, meeting requests, distribution lists, task requests, journals and notes. Once all items are recovered OST file tool provides the user with four options i.e. PST, DBX, EML and MSG to save recovered email items. To convert OST file to PST, OST file tool supports MS Exchange 5.0, 5.5, 2000, 2003, 2007 and 2010, MS Outlook 97, 98, 2000, 2003, 2007 and 2010 and Outlook Express 4.0, 5.0, 5.5 and 6.0. Free demo version of OST file tool is also available, which enables users to experience software functioning before making actual purchase. The demo version extracts email items from unusable OST file and displays preview of them. However, to save these extracted email items, full version needs to be purchased.