anyone can host an email service
Eh, no. You could in the 2000s, nowadays spam protection is so tight, and necessarily that tight, that you need at least a full-time position actively managing the server or you’re getting blacklisted for some reason or the other. Other servers will simply not accept emails sent by you if you don’t look legit and professional.
Definitely possible for a company with IT department, as a small company you want to outsource it (emails being on your domain doesn’t mean you’re managing the server), as a hobbyist, well you might be really into it but generally also no. Send protonmail or posteo or whoever a buck or something a month.
I’ve been running mine for just over 5 years now - initial setup was ass, but it’s very much hands off now - email simply doesn’t change anymore.
If you have a domain to test - I can host it for you. If you then decide that it works well enough for you - I’ll show you how to set it up on your own server.
