OST files are the Offline Outlook data files that store a copy of Outlook emails on the local machine. An OST file has the benefit that you can access these emails without internet connectivity as a local copy of mailbox is there.
While configuring your MS Outlook with Exchange or Office 365 account, you have the option to enable Cached Exchange mode. When you enable Cached Exchange Mode, Outlook downloads a copy of mailbox items to the local system. And while enabling Cached Exchange mode, there is an option to select the synchronization time in months.
The procedure of turning on Cached Exchange Mode is quite easy; you need to follow below mentioned steps (here I am using MS Outlook):
Apart from its use for offline working, the offline Outlook Data (OST) files are helpful in many ways. Exchange administrators can use them to restore deleted or missing user mailboxes. Also, some other situations in which they become useful are:
In all these situations, Exchange administrators convert the OST files on the user systems to PST files to retrieve the user mailboxes.
If you are facing any of the above mention issues regarding Exchange, then you should use a third-party tool for converting OST files to PST. Kernel for OST to PST Converter is an amazing tool for converting even damaged OST files to PST. The OST to PST Converter software performs complete OST recovery without impacting the originality or the hierarchy of the mailbox data. If your OST file is oversized or damaged, then you can convert it to PST and split it into small and independent chunks of PST.