Feels weird to ignore the largest players, e.g. Fastmail or Protonmail
This is because like most other vendors, they do price discrimination based on number of users. Which is no doubt why the other large vendors were also ruled out.
One vendor who doesn't do this is Migadu. I don't use them as they lack 2FA support, but they are one of a small number of businesses who make their proposition easy to evaluate quickly, as opposed to making you swipe through a pitch before you get to the facts. This is so unusual that I remember them despite evaluating them multiple years ago.
That makes emails forwarded from, say, PayPal or ebay marked as scam/phishing in Gmail, AND makes it impossible to report actual spam that comes through.
With a well set up SRS all these emails are recognised correctly. SimpleLogin does some naïve forwarding which messes it up.
I'm migrating out of them exactly for this reason - if I could do it on my hobby server for my personal domains, THEY should be able to do it as well.
I can't find that in his list of requirements. He said he wants unlimited addresses, but I'm not able to spot any mention that he wants to send from all those addresses. A catch-all will work just fine for receiving mail, so it may be an option for him.
Although to be fair, I welcome competition, and I like seeing people end up with other solutions. I would hate it if Protonmail and Fastmail were the only viable services offering this.
An example of a company that does exactly what I pay them to do and respects me as a customer.
I am definitely engrossed in the Apple Ecosystem™ though so I can't speak to how it would fit any other setup that isn't almost entirely Apple-based.