When using thunderbird it occurred to me that it was using a lot of CPU cycles, usage of 53% were almost constant while thunderbird seems to be idling. That’s not the way.

It seems there’s a bug in thunderbird <= 17.05 (and perhaps in newer version also) that was causing this

It can be fixed by setting mail.db.idle_limit  to 30000000 iso 300000 

Be sure to check the number of zeros 🙂

You can get to that setting by going to edit > preferences > Advanced > Config editor and use the search box to find the option.