To remove duplicate items from Outlook PST files, using a dedicated tool like Outlook Duplicate Remover by vSoftware is one of the most effective methods. This software scans Outlook data and detects duplicate emails, contacts, calendars, tasks, and notes based on multiple comparison options. Users can safely delete or move duplicates without damaging original data. The tool is easy to use and works with all major Outlook versions, making it suitable for both home and business users.

You can check the complete details - https://www.vsoftware.org/outlook-duplicate-remover.html