Nobody else has tried to help you, so I will try. I have hesitated to try before now, though, because I'm not going to install a french version of Thunderbird to test things. Try this: Thunderbird menu: Tools: Options: Attachments section: Incoming tab (If you cannot see the Thunderbird menu, press the Alt key or F10 key on your keyboard to show the menu) You see the window I show in my screenshot below. Remove/delete the entries for the problem types (select them, then press the delete button on the keyboard). Quit Thunderbird, then start it. The first time you try to open one of those attachments, you '''should''' be prompted to choose the program you want to open it with.