To convert an Outlook OST file to a PST file, use SysInspire OST to PST Converter application. It's a powerful application that can convert Outlook OST files to PST and a variety of other formats, including EML, HTML, Yahoo, Gmail, Office 365, MSG, ICS, Zimbra, MBOX, and EMLX. It also offers a money-back guarantee as well as technical assistance. It is compatible with all Windows operating systems and Microsoft Outlook versions, including 2019, 2016, 2013, 2010, 2007, and 2003. Get 25 mailbox items from each folder in the free demo version of this tool.