Z 4 z 5 hwěžkow pohódnoćeny

I know about that. Right click Folder and click duplicate messages...; A window appeared and showed me all duplicate things, I followed the instruction, and click on duplicate list (left click) for message to display, but nothing happened ?? I use thunderbird 3.1.15

Tute pohódnoćenje je za předchadnu wersiju přidatka (0.1.10).  Tutón wužiwar ma druhe pohódnoćenja tutoho přidatka.

Did you click or double click the messages? Actually the state of an E-Mail should toggle between "KEEP" to "DEL" when you double click them.