There is also mailcow. I've been using mailinabox for years now, and it is really good in the sense that it gets out of my way. I've included it in my ansible

There is also mailcow. I've been using mailinabox for years now, and it is really good in the sense that it gets out of my way. I've included it in my ansible setup, so the basis, distro, os updates, firewalls, backups are cositent with my other servers. That took some effort: mailinabox is opnionated (and that is good. It is the main reason it works well and is secure), which can be a bit confronting if your opninions are very different.