* Every thread that mentions hosting your own email brings out the it's-pointless-do-do-your-own-mail zealots; ignore them. If you're interested in trying it, try it.
* The only deliverability issues I ever had were with ATT networks because they don't use modern TLS; that was fixable. Mail to Google? Goes through, doesn't go into spam. Mail to Microsoft? Ditto. And this is on a Digital Ocean VM, which isn't the most reputable IP pool in the world.
* MIAB will happily be your full-fledged authoritative DNS server. Although I've since migrated to separating DNS from mail hosting, it was very convenient for a long time.
* Setup is dirt simple. And you get MTA-STS as well as DANE/DNSSEC right out of the box.
* The backup function worked without issue the one time I needed it. I'm sufficiently paranoid that I also do regular snapshots of the whole VM.
* There's a fork, Power Mail In A Box, that updates the UI, adds the ability to plug in relayhost settings, and does a few other nice things. It hasn't been updated in about a year, but was similarly solid.
My only quibble with MIAB, and the reason I migrated to Mailcow recently, is that I wanted to easily set up per-domain relay settings from the UI.