Try the safest solution called eSoftTools OST to PST Converter software to recover lost OST mailbox and Convert OST to PST file. Through this unique technology, users can convert OST files into more than 9 file formats, and can also import OST items into cloud email platforms such as Gmail, Office 365, and Yahoomail. For a quick demo of this software, you can download a trial version that is provided to every user for free.
For more info- Convert OST to PST file
For more info- Convert OST to PST file