Too bad the author didn't check Fastmail. It checks all the boxes and on top of that its, imho, the best finished product for mail / cal / contacts and by far.
It may even be my favorite tech product at all. Should I be able to pay for more storage space for the drive (options are very limited), it would approach the perfection.
Fastmail is expensive. The author mentions Purelymail at around $10/year compared to $60/year for Fastmail.
Sadly their website seems to break on older devices - https://ibb.co/album/99kr9z
Email is one service that should be accessible from any machine.