This is when the question crawls in his mind that how to open OST files?
Simple! You can very easily OST Conversion to PST. In this undertaking, you get to open OST in Outlook. Such an endeavor where you put our software to use to open OST file, you would most definitely result in advantageous outcome when you would finally be able to open & convert OST files to PST.
Part 1 : Remove Encryption from OST file (S/MIME-Open PGP with Single Key)
Part 2 : Decrypt OST file Encryption (S/MIME-Open PGP with Multiple Keys)