If you're looking for software to help you convert OST files to PST files, I recommend eSoftTools OST to PST Converter. It perfectly migrates OST data objects into PST format, including addresses, calendar entries, contacts, emails, assignments, notices, and so on. We can translate OST to PST without installing Outlook.
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if you want to restore you outlook ost mailbox items and search any best tool to restore your ost file data try stella outlook ost restore software to restore all ost mailbox items like emails items, contacts items, calendars items, task items and many other items in to office 365 account this software is restore all 32bit and 64bit ost mailbox items and install all windows operating systems this software is specially design to restore all ost file data without deleting any ost file this software is restore all ost file using some simple steps. For more info visit this link https://www.stelladatarecovery.com/ost-to-pst-converter.html