While I agree with pretty much all you wrote, I'd like to point out that e-mail, out of all the services one could conceivably self-host, is quite resilient to temporary outages. You just need to have another backup mail server somewhere (maybe another self-hosting friend or in a datacenter), and set up your DNS MX records accordingly. The incoming mail will be held there until you are back online, and then forwarded to your primary mail server. Everything transparent to the outside word, no mail gets lost, no errors shown to any outside sender.