To get back OST files soon, you can try BLR OST Recovery tool. They said it is a very handy tool to access corrupted OST files which are located in inaccessible mailboxes. It deals with numerous OST files also, and it does the job extremely fast. It specifically restores OST files and converts it into Outlook PST file format, but you can also export into EML, HTML, MSG, vCal and vCard formats.
https://www.blrtools.com/ost-to-pst-converter.html
