I went up this road. I ended up settling on Mailcow because it does all this same work and more, with pretty good integration and sensible choices, together wit

I went up this road. I ended up settling on Mailcow because it does all this same work and more, with pretty good integration and sensible choices, together with some valuable tools for things like migration and backup. If and when the Mailcow project goes away, it’s all still standard components, so moving to i.e. vanilla postfix and dovecot should be straightforward.