No offense - but what exactly is so unreasonable about that? A company can function as formally as it wants to. If you were required to wear a full suit and tie to work every day, and wanted instead to wear khakis and a polo shirt, a company would be nowhere near out of line in asking you to conform to the dress code. The same applies with correspondences, particularly since email is quickly replacing standard paper letters. If you don't like the policy, then petition it to someone higher up than that guy. Or, just quit. Just my two cents.