Funny headline, because every time I try to self-host anything important like mail, I learn how deep that field is and how little I know and that I'll probably need many many hours to do everything right and in a secure way (and my mails would still have a higher probability to be classified as spam). Then I think: "Screw it, I'll just use GMail"
Email is basically pointless to host yourself from a privacy perspective. Every email has one or more people on the other end that also get a copy. Privacy and email are mutually exclusive. That said, the alternative doesn't have to be something like gmail, where they can do whatever they want with your data. I use Fastmail and that's "sufficiently private" for my needs.