Mailcow internal on Debian VM. SMTP2Go free external relay. Have had the occasional issue after an upgrade or reboot can’t find my LetsEncrypt cert and will bork the system until I manually fix it. Perhaps my latest script update finally resolved that. Otherwise, not that bad. Been running my own email for about 5 years or so. I don’t sign up for many outside services with it. It’s mainly for internal alerting or testing purposes but still works very well.