stella ms office ost converter software is the best software to convert all ost mailbox items in to pst file this software is convert all corrupted and unmounted ost mailbox items in to pst file this software is convert all version 32bit and 64bit ost file this software is convert all ost mailbox items like emails, contacts, calendars, task, notes and many other item in to pst file. for more info visit this link https://www.stelladatarecovery.com/email-migration/ost-to-office-365.php