not for me.
There is a paradox of sending an email. The more you sent email, the more you receive email. So, i think, gamification is not right answer.
I've never really understood the fascination with zero inbox. I think it's focusing on the wrong problem. I really don't care if I have 10k emails in my inbox so long as I'm on top of the important things. The pressure to clear my inbox is unneeded anxiety. Counter-productive...
introduce
Wyndy