On non-Windows, there is an Email section under Internet Options .
The dialog needs a notice that the server may be left empty, in which case it will attempt to detect client automatically, to not create an impression that the field is required. There is a code  that uses xdg-email, etc. to be smart in finding mail client :)
Possibly documentation (help, Getting Started Guide ) should mention that as well.
I agree that adding that notice would clarify things.
Version: 220.127.116.11.alpha1+ (X86_64) / LibreOffice Community
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