I recently switched to Fastmail. When I was asking an LLM about using it with the native Apple apps, it mentioned this approval that was needed, and that it didn't always work. I'd be interested to hear some first-hand experiences.

My dad has been using his own domain for email for about 25 years and has bounced around to various hosts... random hosting providers. He uses Apple Mail and hasn't ever mentioned having an issue. Though I'm unsure if he uses push of fetch. I guess I always assumed he was using push, but maybe not.