@drhaywardj @chetwisniewski you should have a look at the upcoming kickstarter for Run Your Own Mail Server by @mwl - https://www.kickstarter.com/projects/mwlucas/run-your-own-mail-server
I’ve been running mine since early 2000s and (as a sponsor of the book) I received a prerelease copy. It’s a great resource for what’s necessary to do this important work in the modern climate. Highly recommend it.