The best and the top way to use the fully free
VSPLOST to PST Converter tool is a powerful solution to export unlimitedOST files to Outlook PST file format. It migrates and migrates single and
multiple OST files to MS Outlook PST file formats without any data loss. The
Graphical user interface is very intuitive so you do not need any technical
expertise and you can simply transfer data from OST to PST. It is one of the
best software available to migrate your OST files to PST. It offers a free demo
version that migrates an initial few emails from each OST folder for user
satisfaction.
More info - https://www.vartikasoftware.com/product/vs-ost-to-pst-converter-software.html