If you are seeking a solution to add OST files of Outlook to PST, then you can go with WholeClear OST to PST Converter for Windows, which can transfer Outlook OST files to PST documents. It can convert a configured Outlook data file to a PST file directly. It can save all OST files into PST at once. It provides a free demo edition to check out its working process and allows a few email migrations from Outlook OST to PST at of cost. Read more: Refer: https://www.wholeclear.com/ost/pst/