This section of their website says no telemetry reports are submitted:
https://www.betterbird.eu/legal/index.html?ref=news.itsfoss.com
It does also say that some data may be submitted to Mozilla.
I’ve been looking for a good alternative as a precaution. Evolution Email seems the next most popular but it keeps logging me out of my accounts every few hours. I might try Betterbird or Claws Mail.
For Android I’m using FairEmail as mozilla bought k9 Mail.
Is Waterfox a good alternative?
I keep having to log in on Evolution. If I knew what I was doing I would stay on it but for now I’m on Betterbird.
FairEmail is a good switch for Android.