Rated 4 out of 5 stars

by happyboy1992 on Sept. 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). 

by Thorsten W. Schmidt (Developer) on Sept. 28, 2011 ·

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