I'd run my own email server since the early 2000's - in several forms over time. A VA Linux 2U rack server that I got from work (noisy, overkill), a personal Mac Mini (Frankenstein macport upgrade-resistant), and now a single-node k8s instance with everything neatly managed (an excuse to really dive into k8s from the ground up).

I use dyndns to handle IP changes (incredibly rare with Frontier FIOS, actually). I use mailhop.org to handle secondary MX records in case my machine is down (as well as mail filtering) Everything else is postfix, spamassassin, dovecot imap

It's not a trivial system, and it took a while to get everything working how I wanted. It's a terrific learning opportunity, but it's by no means simple to mentally model the process of all that happens inside.