Rated 4 out of 5 stars

yazan: happyboy1992 tarih: Eyl. 28, 2011 ·

It'd rather good add-on; however, I cannot see duplicated emails by using left click

This review is for a previous version of the add-on (0.1.10). 

yazan: Thorsten W. Schmidt (Geliştirici) tarih: Eyl. 28, 2011 ·

You need to do a right click on a folder. There you can select 'Remove Duplicate Messages ...'