Try ost to pst converter
full version from KDETools software. This is the unique solution that has ability to transfer emails, mails from damaged OST to PST file format with all mailbox items like: emails, contact, calendars, inbox folders, sent items, draft, deleted folder items, journals, appointments etc. This software is capable to run on all Exchange servers and MS Outlook versions (97 to 2016). Through this utility you can simply works to export OST to PST in Office 365 or other files like Zimbra, Gmail, EML, EMLX, vCard, ICS, MSG, PST, Live Exchange server, MBOX and etc.
More info- how to convert ost to pst