Most of time by virus attack Outlook file getting corrupted and for Convert OST to PST users need a third party tool and the best third party tool who help to be back from problem it is Stella OST to PST Converter software Stella give you always best service with best support team any time. It will have a demo version by help of that you see all the preview of your mails and recover 25 mails easily.
For More Information: https://medium.com/@danielchrishtan/stella-microsoft-ost-to-pst-converter-recovery-software-ecc6e9d5c780
See the process of Stella OST to PST Converter : https://youtu.be/CSaLnzypSYY