What do you understand by OST File Format?
OST file format stands for offline storage table which gets created automatically though Microsoft Outlook offline folders feature. Offline storage table active when Exchange connectivity gets offline & synchronizes all updated email information when exchange turns online. In this file store, email messages, attachment, contacts, journals, notes, calendars etc. OST file format help users to work offline even the exchange server dismounted or down. OST is created in collaboration with MS exchange server that enables user to work with their messages & mail data. In offline case, when user try to send or receive email through your Microsoft outlook it asks user to create OST (Offline Storage Table) file because MS outlook get established properly.
If user are using Microsoft outlook as a client to an exchange server computer, user data will be stored on the server as usual. Sometimes this is not always the best configuration for users. The concepts of offline storage allows you to essentially carry on working in outlook even though you are not connected to your primary exchange server systems.
Offline folders make it possible to take a folder from server path, work with the contents of the folder when you are not connected to network & update the folder and its correlate server folder to make the contents of both identical. User can easily modify , add & delete the contents of an offline folder exactly as you can with a folder on a server. Offline folder are stored in the offline folder (.ost) file. This file is located on your computer hard drive and is available even when the network is down.