I’ve been using this https://github.com/r-raymond/nixos-mailserver for 4 years for my personal mail and I haven’t had a single issue in that time. I think it takes me about the same amount of time as you to maintain but I also have a next cloud server running on the same machine.
Looking for freelancers with a couple of years of experience in software deployment, especially python. Responsibility include coaching data scientists on code quality, setting up continuous testing and deployment pipelines, troubleshooting applications and managing virtual environments.