MailsDaddy OST to PST converter is the best tool for the conversion of OST files to PST files as well as in many other formats- HTML, MSG, EML, EMLX, etc. The tool also preserves read/ unread emails and also provides a date filter. It maintains the same hierarchy of the folder with the same HTML and same text format. You can use a free demo of MailsDaddy OST to PST converter and export 20 items from each folder.