Josh, I know that you’ve expressed a desire to focus on DNS-on-the-box. I think that optimizing for that makes total sense for a big set of users, but also is a blocker for other major uses.
Right now, my Mail-in-a-Box is being configured to do its own DNS. This is easy because I’m not using that domain for anything else (it’s eric@ericmill.com). It’s nice to have all the DNS just work, and keeps the instructions very simple, and doesn’t need DNS provider-specific instructions.
But if I wanted to actually migrate from my main email address (eric@konklone.com) to a Mail-in-a-Box, that implicates a lot of other subdomains and infrastructure that are currently managed in my external DNS provider (in my case, iwantmyname). I would be very loathe to suddenly have a suite of services all depend on the DNS managed by Mail-in-a-Box, whose tools and instructions are naturally optimized only for the DNS records needed for its own work. I would absolutely make the tradeoff of having to manage DKIM/SPF/DNSSEC/DANE records myself in this case.
Even if the main guide optimizes for DNS on the Mail-in-a-Box, I think managing DNS externally should be an officially supported path for Mail-in-a-Box, with a guide that handles just that aspect of the process, for people who want that to use.