Check how many long running, recurring appointments you have.

> high CPU usage until I refresh the calendar.

By this you mean, you start Thunderbird and it has high CPU. Until you click a calendar (you only have one calendar?) and pick "synchronize?

I have no recurring appointments.

Until you click a calendar (you only have one calendar?) - Yes after startup

pick "synchronize? - not an issue

The problem still exists. When I start Thunderbird the CPU usage goes to 12-15% until I switch to the calendar then is drops to 0.0-0.2%. The same thing use to happen with older version of this program that was eventually solved.

See https://support.mozilla.org/en-US/kb/profiling-thunderbird-performance for instructions on create a profile.

Here is the result of the profiler.

https://profiler.firefox.com/public/acnqgrm5bndv34czg9z6t915xya4v5b0yfr1q7r/calltree/?globalTrackOrder=0w2&hiddenGlobalTracks=1&hiddenLocalTracksByPid=4420-0w2~7824-2w5&thread=0&v=10

Thanks for the profile.

1. Does it help to remove status bar from View? View > Toolbar > Status bar 2. Does it help to select a folder that does not have many messages?

selfsimilar, Please post your results. Thanks

Thanks for the profile. 1. Does it help to remove status bar from View? View > Toolbar > Status bar 2. Does it help to select a folder that does not have many messages?

The notification system had been broken, so posting again to be sure you saw my response earlier.

If you still have trouble, please post more detail.

Thanks for the profile. 1. Does it help to remove status bar from View? View > Toolbar > Status bar 2. Does it help to select a folder that does not have many messages?

Yes = turning on / off the status bar increases and decreases the CPU usage until the calendar has been brought into focus then it has no effect

Can this be fixed?

Can this issue be fixed?