Well, as someone also self-hosting email I agree with his solutions but he paints a picture of how bad it is that I feel is a bit exaggerated. But then again I host for myself and my family, I suspect it gets a bit different when you have many users and send hundreds of mail per day.

Only one I’ve had trouble with it Microsoft, they’re the strictest and you need to get some support from them to make it work reliably. Google has an automated service.