OST files are stored in MS Outlook Exchange Server, they can not open if in any case exchange Server crashed or undergone maintenance then you need to convert OST files to PST format to view or open OST data file. For effortless solution to convert OST data files to PST format, You can make use of EmailsGuru OST to PST Converter software. It easily convert offline OST files to PST format including emails, contacts, notes, calendars, attachments, etc. The software ensure data integrity and folder hierarchy of OST files in resultant PST files. This tool automatically remove duplicate mails during migration of OST files to PST. It is compatible with all latest and old versions of MS Outlook and Windows OS.