Ask HN: Best tutorial on how email works?

I've been working on installing Postfix, Dovecot, OpenDKIM, OpenDMARC, and Roundcube on my own AWS instance lately. It's going OK... I've begun to become curious about how exactly email works on a network level. Perhaps if I understood that better, I would be better equipped to get what I'm trying to do done. There are thousands of articles out there when you search "How does email work?" on Google. I assume HNers could point me in a better direction that Google could on this matter, however.