I'm running Thunderbird 56.0b3 on macOS 10.13.1 public beta 2 This week I've had a couple of times the problem that a process called thunderbird (not Thunderbird, and without the little icon) is shown running and using 58-59% of CPU. Needless to say, this makes the fans on this Macbook Pro mid-2010 run noisy. Now I know to check this and to do a Force Quit of the process. But there's a problem with Thunderbird on Mac.