OST Leave feedback On this page FileType.OST field See Also FileType.OST field Outlook Offline Data File (.ost) represents user’s mailbox data in offline mode on local machine upon registration with Exchange Server using Microsoft Outlook. Learn more about this file format here. public static readonly FileType OST; See Also class FileType namespace GroupDocs.Viewer assembly GroupDocs.Viewer Was this page helpful? Not really Yes, thanks Any additional feedback you'd like to share with us? Skip Send Please tell us how we can improve this page. Skip Send Thank you for your feedback! We value your opinion. Your feedback will help us improve our documentation.