If you want to remove duplicate emails in PST files, then I can suggest the best tool becouse I'm also using so you can try the TrustVare Outlook Duplicate Remover without facing any issues. The software automatically scans PST files like emails, contacts, notes, tasks, calendar, etc, finds duplicate items and removes them without affecting your original data. The software handles a lot of duplicate PST files without downloading any other application. The tool is capatible with all Windows OS versions like 11, 10, 8.1, 8, 7, and it also supports Outlook versions. The software has a very simple UI for non-technical users and they don't need any technical skills. They can use a free trial before buying this tool, and after removing duplicate PST files, it will give you a preview and the results.