Manually conversion of offline OST files to PST format is possible but It is very lengthy or data loss can be take place. So here I am suggesting you professional’s recommended EmailsGuru OST to PST Converter software. This tool gives single step solution to convert OST files into PST format. The software have unique user-friendly interface which smoothly convert OST to PST files without any risk. This utility also facilitate users to convert selective OST files into PST format. The software runs on all versions of Windows OS and supportable to all editions of Microsoft Outlook.
for more details: https://www.emailsguru.com/ost/pst/