Nice!

So I looked at a few of these dockerized systems before, and maybe it was bad timing, but they all had bad CVEs related to the UIs that were slapped on top of mature services which turned me off to them when I was thinking of changing.

I've been running https://github.com/docker-mailserver/docker-mailserver for many, many years now and it's great. It has the absolute basics (postfix, dovecot, etc) so configuration might be harder for those unfamiliar, but it's rock solid simplicity.

I run one as a relay, and another in my home lab where everything ends up.

Well congratulations!

But low bar to clear etc etc