Not looking for a server as I use fastmail currently but a client would be nice. I am currently using spark on iOS and Mac OS and just fastmail website on my Linux desktop. I’m realizing spark is nothing special and would rather not renew my subscription.
Spark was pretty convenient until they changed to a subscription model, removed a bunch of features, and completely fucked over everyone who paid for a lifetime membership.
Idk if it’s available for iOS, but Fair Email is an amazing email client. It’s privacy focused, FOSS, and works well. Anything else will be inferior, either costing money, tracking you, uploading all of your emails to their server, or any combination of those things. You can try K9 email if it’s available for iOS and Fair Email isn’t. It’s a similar app to Fair, but hasn’t been updated in a long time on Android.