When manual cleanup didn't remove all duplicates from MSG files, you should try the best tool for it. Use the TrustVare MSG Duplicate Remover, which quickly finds duplicate items in the MSG files and removes them without harming the original data. You don't need technical skills to operate it becouse it has a simple interface. It will handle a lot of duplicate MSG files without installing any other application. The software supports all Windows OS versions like 11, 10, 8.1, 8, and 7. It provides a free trial before buying this tool. You should try it and see their removal process.