I have been using Outlook for the longest time and have tried FairEmail a couple of times and simply deleted it. Tried sticking through it for about a month and I'll be sticking with it for a good long time now :)
I actually swapped to Protonmail last night. Took awhile to change the email address on everything, but worth it. Trying out the free version for now, keeping my Gmail as a backup and for Android.
It's really good. I have a visionary account now and am very happy with the services. They have matured a lot over the last few years. I'm happy to pay for the security and not being a product.