I find this sort of hard to believe that this bug made it through beta testing (let alone alpha) - this isn't some strange combination of things but just,for me and others on this forum, happens with a variety of mail providers and happens all the time. Please just fix it
Mail has become a peripheral, unimportant function for Apple. Apple doesn't seem to care whether you can use an iPhone for email or not. The primary mission is to provide a platform for sales of services such as Apple Arcade, News, Music, TV+, Apple Pay/Apple Card and of course the App Store and iTunes Store.
/sarcasm