I wanted my own domain and a good integration with android but I didn't want to give my data to microsoft so I went with https://www.ovhcloud.com/en/emails/hosted-exchange/
Had no issues so far for the last 2-3 years.
It's cheaper than protonmail and you're not locked to a specific application since Exchange is well supported.
100% solar energy? They shutdown the servers at night?
The site says 100% green but hosted in Germany. I'd be curious to know how this is possible