Mail merge to email does nothing

LO on Windows 10
Everything is set up correctly - the test of SMTP server works with no errors.
When I click “finish” at the end of the wizard process, nothing happens. No emails get sent at all. the addresses are all fine I know because they’re all mine!
No error messages at all.

Do you have set the default app in Windows?

See also:

yes. It doesn’t seem to matter what is set as default email client - nothing happens.

Try this registry key:

Windows Registry Editor Version 5.00
@="Mozilla Thunderbird"

Nothing happens in Mint 20 either. Document Preview is OK, press “Finish” - absolutely nothing. No emails generated at all.