From Brana Bujenovic:
Detect Duplicates for Windows Live Mail is powerful duplicates detection and removal tool for Windows Live Mail. It maintains an ordered mail-folder and message system by detecting duplicate messages under a variety of conditions and according to a variety of user-selectable and configurable options. This will enable you to keep your mail in the kind of order that makes the most sense for the way you prefer to conduct your life, your profession, or your business.
What's new in this version:
This release has faster RegExp matching and includes a workaround for WLM's "abbreviated folder names" issue.