You can convert OST file to PST file format. You can try this software Toolsbaer OST to PST Converter Tool. This tool Support all Outlook version including 2003, 2007, 2010, 2013 and 2016. The free Trial version which transfers the first 10 items from each folder. The tool safely exports emails, contacts, calendar entries, notes, tasks, and much more into PST format. Download the free trial Version for OST to PST Converter Tool.