I tried to create subfolder "2015" in "Local Folders". The dialogue window did not close after pressing "create" and I waited already serveral minutes. Up to now there are 14 subfolders in "Local Folders", 5 of them empty, the others have 2 subfolders each, each filled with some hundred emails. Work-around last year: Create "2014" as subfolder in "2013". I checked the properties of "Local Folders": Location is correct: $HOME/.thunderbird/lcdfycqz.default/Mail/Local Folders When I confirm that location I receive an info box with the message: This folder is invalid. Please choose another folder (I translated the text displayed to English). Up to now I do not want to create a different local folder because I fear data loss. Any ideas?