It sounds like you have accidentally copied, moved or created folders. I've seen this happen with people who use laptop computers, because when using the touchpad, unintended things happen easily like moving folders. If you are using a touchpad, then that might be what is happening. Try plugging in a mouse and use it instead. You will have to sort out the folders yourself. To rule out problems with Thunderbird, follow these instructions to rebuild the folder indexes and do cleanup. '''1.''' Find & open your Thunderbird Profile folder: Select Help: Troubleshooting Information from the Thunderbird menu (either from the menu button , on the top right, or the normal menu at the top of the window.) Under "Application Basics", beside "Profile Folder", click the "Show Profile" button.  This will open a window showing the contents of your Thunderbird Profile folder. '''2.''' Quit Thunderbird, but keep that window open showing your Thunderbird Profile folder. '''3.''' Delete "global-messages-db.sqlite" and "panacea.dat" from the profile folder. '''4.''' Start Thunderbird. '''5.''' Select one of your accounts on the left side, then Empty Trash and Compact Folders: a. Press the ALT or F10 key to show the menu bar. b. Click on File: Empty Trash c. Click on File: Compact Folders. '''6.''' Do step 5 for each e-mail account, then the Local Folders.