So as it says in the title I have tried to set the default several times from different angles and no such luck. I’ve read through several other people making the same statements and tried some of those suggestions but with no resolution.
If your Windows is not settings eM Client as default mailer in the usual settings place, then you might have a possible registry problem. Make sure to reboot after setting default.
Also see this thread for more info how to set eM Client as default if you have eg: Windows 11