Running my own mail for 20 years, I've never experienced any of the commonly cited problems re delivery to cartels like Gmail etc, but YMMV there... Tech wise,

Running my own mail for 20 years, I've never experienced any of the commonly cited problems re delivery to cartels like Gmail etc, but YMMV there... Tech wise, in the old days it was sendmail and pine/mutt/etc, more recently courier, these days postfix and dovecot. I wouldn't ever consider outsourcing something as crucial as email as it's not e2ee and being able to diagnose delivery issues and fix them quickly is very important. Also related: former mailop