Outlook 365 accounts and others store information in Offline Outlook Data Files. Those are OST files. An OST file allows access to emails without Internet access. Changes made offline sync when back o...
Outlook 365 accounts and others store information in Offline Outlook Data Files. Those are OST files. An OST file allows access to emails without Internet access. Changes made offline sync when back online. OST files are created with the “Use Offline Folders” option in Outlook. Software that can open OST files include Microsoft Outlook 2016 and other applications.
OST files store Outlook items saved on your computer. The Windows Registry associates OST files with software to open them. OST files contain email, appointments, contacts, and messages. File specifications for OST and PST formats come from Microsoft’s Open Specification Promise.
Elements of the OST file format include file header data, index nodes, index leaves, and offset indexes. OST files are Outlook Offline Folder Format. Many files contain only simple text. One way to open unknown files is to associate the file extension with software in Windows Registry.
Microsoft Outlook
Exchange Server