Thunderbird mail’s telemetry information is transparent and privacy-sensitive, but there is also Betterbird which is a soft fork of Thunderbird mail client
Thunderbird e-mail client does collect some basic information about installation numbers, versions in use, crashes, add-ons, etc that relate to technical data and which does not identify individual users. This defaults to ON, but can be disabled by users. It does also have a category called "highly sensitive or clearly identifiable information" that defaults to...
