It is helpful to include some information when posting a question. What OS do you use? What version of Thunderbird are you using? Please restart Thunderbird in 'Safe Mode' Assuming 'Help' is still working..... Help > Restart with Addons disabled small window opens select checkbox : 'Reset toolbars and controls' Click on 'Make changes and Restart' Does this fix the issue ? If yes, great. If no. Perform another start in Safe mode but this time click on 'Continue in Safe Mode' If this fixes the issue then please check your addons. Disable an addon extension and restart If it is ok then you know that particular addon is causing an issue. It might need updating. If still an issue even in Safe Mode and after resetting toolbars and controls. Please post an image showing the problem.