And when you add a new account you have to do that for all the folders individually. That doesn't apply to a folders sub folder either. There is a method to copy all settings to a folder and its sub folders but that does not include sub folders of the sub folder. So you end up for a while with some folders showing up as threaded and some not. And you have to do it for each account individually. (some of us have multiple accounts for businesses and personal emails) Nightmare when deleting, because you may delete a thread rather than an individual email. For most of us it means threading was foisted on us without notice or discussion. Ever tried to find out what is being considered? Good luck with that. Surely a global button to remove all threading can't be all that hard.