OST stands for Outlook Storage Table. It is one of the most used email file formats of MS Outlook, developed by Microsoft Corporation. The file extension stores and manages email data well.
The prime benefit of the storage table is that it allows users to continue their work even if Outlook is disconnected from the Exchange Server. It is why OST is best known as Offline Storage Table. It allows users to write new emails and saves them in drafts. The Outlook connects automatically to the server once the server connection comes back and starts sending and receiving all pending emails. Apart from this, OST is capable of retaining the lost mailboxes if any damage occurs due to server errors. The carbon copy of OST files are saved to the hard drive of your computer that helps to restore these files. Therefore, the file extension is used widely for Outlook data management.
Like PST, the Offline Storage Table stores emails (its properties including CC, BCC, Date, Time, Subject and Attachments), contacts, events, journals, notes and messages. It supports Unicode characters too but the MS Outlook is not capable to store large sized files.
\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook