This: https://mwl.link/run-your-own-mail-server.html

I don’t have this book by MWL, but, when I got my first Sysadmin job in 2015, I took over a network almost entirely run on FreeBSD, and I was gifted a couple of other books of his, in particular his ZFS volumes with Allan Jude, and I can say that his work is easy to read and good at giving you the most basic raw facts of the matter. If you really want to understand email, read this book and I guarantee you will get all the information you need.

I am not his marketer, just a person who was helped immensely by his work. He’s on the Fedi as well, you can search in Mastodon.

Understand what a Reverse Proxy is, because you will not escape reading that phrase.

Host things with Docker for now. If you don’t start hosting until you understand everything, you won’t start for a long time and that is silly.

Use Cloudflare for now, because they handle a lot of security stuff for you that you definitely don’t want to screw up. If you don’t know what Cloudflare is, read up on CDNs and why they exist. Their Zero Trust Tunnel is the easiest and safest way to go, as long as you don’t plan to do anarchy or sedition on it, just talk about your household plants and dogs and what not and you’re fine.