vMail OST to PST Converter will very efficiently recover and convert OST files into Outlook PST file format. This tool also converts other formats file such as EML, EMLX, MBOX, MSG, vCal, vCard etc. This tool supports all the latest versions of Windows such as 2007, 2010, and 2013, 2016, 2019, etc. You can try the free demo version so that you can convert 30 emails for free.
Get more info- https://www.vsoftware.org/blog/how-to-split-ost-file.html
Convert OST to PST Manually
Open Outlook and go to the File menu.
Select the Import/Export option.
Choose Export to a file.
Select Outlook Data File (.pst)
Choose whether to export a specific folder or the whole account.
Check the Include subfolders box.
Next, select a destination for the Export, and then click Finish.