Best software to convert OST to PST is to use eSoftTools OST to PST Converter software. This software provides instant results for OST file conversion with high accuracy. This software converts OST file with complete Outlook mailbox with items including emails, contacts, calendar, tasks, notes, etc. It is available for all Windows versions, so use it without wasting much time.
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https://www.esofttools.com/ost-to-pst-converter.html