I used to run mail servers for a university and I also suggest that no one should do this. It's hard enough to get right when it's your full time job. No one wants that kind of headache just for an email address. Do what I do and pay for Proton and stick your domain on it.

Running your own email infra is not at the same level as the usual “self hosting”. Not to mention that email can be critical and missing an important email can burn a lot. Why put in that much effort on your free time, and take the risk?

You don’t build your own fridge. If it’s important and not your strong suit, pay someone to do it for you.