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MS Outlook is a desktop-based email client application, which is used for sending / receiving emails. It consists of two types of storage files called OST and PST that stores all Outlook data such as contacts, appointments, emails, calendar items, journals, notes, tasks, etc.

What is the difference between OST and PST files and why they are used?

Traditionally, Microsoft Outlook supports and works with two kinds of data files – OST and PST. The more common personal data file (.pst) are used for storing data related to IMAP and POP3. A damaged PST file can be fixed quickly and replaced with its backup copy. But, this method won’t work with Offline storage table (.ost).

OST file and PST are similar structurally, but they serve for different purposes.  Unlike .pst file, OST files are used to hold offline copies of whatever exists in Microsoft Exchange server. To make it simpler to understand, OST file is a replica of data stored in Exchange server and it enables users to work offline. You don’t need to backup .ost files, since they can easily be reproduced from the data stored in MS Exchange account.

However, when Exchange server goes down, then all your Outlook data including important emails become inaccessible for an indefinite period of time. If you come across such situation and must get back to work ASAP at all costs, then make use of Remo OST to PST migration tool to safely move your unreadable OST Outlook data into healthy PST and start using it in few minutes.