The best OST file converter program for converting OST files to Outlook PST format is eSoftTools OST to PST Recovery program, which can also be used to recover OST files. In addition to many additional formats, including vCard, EML, HTML, Zimbra TGZ, MBOX, Office 365, Yahoo, Gmail, MSG, ICS, and EMLX, it can convert OST files to PST. This program supports all versions of Windows OS and Outlook and has a lot of options that allow users to convert files very gently. Additionally, offer a free demo version to ensure consumer happiness. The company offers all consumers a 30-day money-back guarantee if this program isn't functioning properly.