hmm.. Strange.. I just got my first Smartphone last Thursday(July 6th 2017)
its a Samsung Galaxy S7 works like a charm... hmm..
the only issue I have with it is the lack of PUSH-Notification support for
ALL FOLDERS... x( its a know issue with the FastMail Devs.... they have yet to add the feature.. as it stands you get notified of new mail filed into the general Inbox ONLY X(