A few days back I tried the eSoftTools OST to PST Converter software to import Outlook OST File to Windows 10 Mail. It supported all versions of MS Outlook such as 2003, 2007, 2010, 2013, 2016, 2019. And run with all windows versions XP, 7, 8, 10, and onward. It allows you to restore deleted emails from PST file. You can preview your OST file data before converting to PST file. It supports conversion of unlimited size OST files within a few moments. Free version of this converter tool permits the 25 emails from each folder.