Or any kind of transactional email, I assume? I've run a hobby website for about 15 years that does not even have a newsletter of any kind, and includes "stop

Or any kind of transactional email, I assume? I've run a hobby website for about 15 years that does not even have a newsletter of any kind, and includes "stop sending me emails" in each transactional email (all users are double opt-in verified), and password resets are still not delivered half the time to gmail addresses.