(This is as much an answer to some of the comments already raised, as to the article - which like most such personal pieces has pros and cons.)

As part of a previous job I used to host email for a small business - this was about 15 years ago. I ended up spending several hours to a day a week working on it; apologising to users, tracing and diagnosing missing sent email and the endless, ENDLESS arms war against incoming spam (phishing was much less of a problem then). The trust from the company in our email operation was very poor and you'd regularly hear someone apologising to a customer because we hadn't contacted them, or answered their email. The truth is much was going astray and staff were relying more on the phone than email because they knew it worked. You might guess from this that I'm terrible at running an email system but I don't think I am. I started moving email back in the late 80s when Fidonet was the thing, so I have some miles travelled. Tools have improved a bit since then, but so have those used by the bad guys.

I still consider one of the best things I did for that company was move our company email onto Gmail Business (which was free for us as a charity) Every single one of those problems went away immediately and suddenly I had a lot more time to do more important stuff. I would never self-host email again despite running several personal servers.

Plenty of people say they self-host just fine, and great for you if that's so. But the truth is you won't always know if your outbound mail silently gets dropped and you have a far higher chance of it arriving if it comes from a reputable source. There are a huge number of variables outside of your control. (ISP, your country, your region, your software, even the latency of your MX or DKIM responses factor into your reputation)

You take the decision on whether any perceieved risks of privacy through using a third party outweighs the deliverability and filtering issues of self hosting, but please don't say it's simple or reliable for everyone. If it's simple for you, you're either incredibly lucky or just not appreciating the problem.