recommend using OST to PST Converter tool to recover and also convert OST files in PST manually. Its available with free demo to give whole satisfaction for all users before purchase the license version. Its tool an easy way for restore of lost OST data from exchange mailboxes. Along with by use its software you can convert many files in Outlook PST, Live Exchange Server, Zimbra, Gmail, vCard, ICS, OLM, MSG, EML, EMLX, MBOX, PDF, NSF, and etc. It can import OST to exchange platform Office 365 without losing data. It can generate a preview before file conversion.