Suppose that somehow due to corruption in the server you lose your OST file, because of which all your email messages, distribution list, meeting requests, folders, posts, notes, appointments, journals, task requests, contacts, etc are lost. To recover from such a miserable condition you need to convert your OST file to PST file using an efficient OST to PST converter tool like Kernel for OST to PST which can be downloaded from
http://www.convertosttopst.co.uk/