You can quickly fix the error by using the eSoftTools OST to PST Converter Software. The tool is easy to use and has good recovery and conversion capabilities for OST files. It locates OST files for conversion automatically and does a full scan of OST files to fix any corruption problems. It gives a live preview of every internal component of an OST file, including the calendar, diaries, and emails.

Learn more: Fix the error OST is not a data file for Outlook OST.