Try Advik OST Converter for 100% accurate results. Using this tool you can convert ost to pst file format for Outlook 2019, 2016, 2013, 2010, 2007 etc versions. Also the tool offers multiple saving options such as OST to PST,  MSG, EML, MBOX, EMLX, RTF, Text, HTML, DOC, Maildir, TGZ etc.
Its an all in one toolkit.