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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.
My suggestion here however would be, since you are switching to Protonmail, to set your domain up with simplelogin.io This will allow you to create email addresses as required for whatever service you sign up with using simplelogin, and have them pointed to one (or multiple) of your protonmail addresses.
AnonAddy is excellent, has a good free tier, reasonably priced premium tiers, open source and self-hostable, with a nice very responsive dev.
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.