Efficient communication in the electronic mail game

The literature on the electronic mail game shows that players' mutual expectations may lock them into requiring an inefficiently large number of confirmations and confirmations of confirmations from one another. This paper shows that this result hinges on the assumption that, with the exception of the first message, each player can only send a message when receiving an immediately preceding message. We show that, once this assumption is lifted, equilibria involving confirmations of confirmations no longer pass standard refinements of the Nash equilibrium, and are no longer evolutionary stable.