Self-hosting email is like making your own butter. It’s possible, but most people don’t want to take it on themselves. Calendar and contacts I’d argue are good candidates to self host. If a config is off and you can’t access them for a day or two, does it matter? But if email is down, you risk missing something important. If you have a trust issue and everything you send is getting flagged as spam? Hard and slow to fix. If the problem you’re trying to solve is Flaky and Unethical Big Tech, I would look at finding another, smaller provider and paying for it. Rolling it yourself is a great way to learn entirely too much about mail servers and spending way too much of your free time on it.