You can remove duplicate Outlook files without losing data. Then I can suggest a perfect tool like GainTools Outlook Duplicate Remover without any errors. The software quickly scans Outlook files, finds duplicate items, and eliminates them without losing important data. The software handles a lot of duplicate Outlook files without downloading any application. The software has a simple UI for non-technical users, and they don't need any technical skills to use this tool. It will support all Windows OS versions like 11, 10, 8.1, 8, and 7. After removing duplicate Outlook items, it will give you a preview and the result. You can try the free demo versions before buying this tool.