100%. I’ve been running my own mail server for 10-15 years now and you’re spot on. I’ve wanted to migrate it to a more modern platform but I’m loath to relive the process of configuring postfix and dovecot. DKIM/SPF and Let’s Encrypt certs for IMAPS were also a bit of a headache to get sorted, and warming up the sending IP so gmail would stop sending me to spam… but once that’s all sorted it’s been very very hands off. I log in once in a blue moon to update it but otherwise it just sits and does it’s thing.
Have used both Zabbix and Prometheus for this. Highly recommend Prometheus over Zabbix if you can afford the time to learn it. It’s a bit weird at first but it’s so much easier to extend and manage then Zabbix in my experience.
You will need to set up Grafana to go along with Prometheus. But, again, it’s so flexible that you will end up being happier with it.