For nearly everyone this is a spectacularly bad idea, other than to gain some experience with Linux/Unix administration/configuration/infrastructure.
You will waste a LOT of time getting it set up and fiddling with it. It's pretty funny that the second heading in the article is titled "Fewer Distractions".
Just use Gmail and spend the time on something more worthwhile. The die-hards who still, in 2020, complain about HTML email are just wrong and absurd. Contrary to what they say, HTML email is very useful for discussing code: e.g. the ability to send well-presented syntax-highlighted code fragments for discussion is helpful, not a hindrance.
Really, I feel the same way about projects that insist on doing development by email. There was an appallingly arrogant and ignorant comment on emacs-devel the other day about how much superior Emacs' development practices are to the "entitled kids on GitHub" who just "shoot off a PR" and say "here it is can you check it in".
Just use PRs and just use cloud-hosted HTML email via a web client and get on with important things, and enjoy the new technology.