Now this is interesting... Appreciate it

Or https://www.iredmail.org/ or https://cloudron.io and https://mailcow.email/

Cloudron.io is closed source and hosted, I believe.

Mailcow only does smtp and pop/imap, no dns, CardDAV and CalDAV.

Iredmail looks neat!

Thanks!

It's not hosted - you install it on your server. https://cloudron.io/get.html. Why is closed source an issue? gmail, helm etc are all closed...