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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
I've been running my own email server for the last 10 years or so using iRedMail / CentOS on a cheap VM. It requires very little maintenance and I never have problems with delivery (just make sure you have DMARC, DKIM, SPF, all setup).
Occasionally I consider moving to service provider but I don't really trust any of them with something so important. Especially Google, as there are so many cases of people getting locked out of their account with virtually no support available to them.
If I were going to switch to a provider, it would likely be Proton. They are based out of Switzerland and as far as I know have an outstanding reputation.
https://proton.me