I'm going out on a limb, but I'll take a stab at AR 25-50. I found all the proper ways to address written correspondence, and right at the front of the AR it says you should use face to face meetings or telephone calls for correspondence when possible. I know it's in there somewhere, but I don't have time to hunt right now.
Posts: 79 | Location: Portsmouth, VA | Registered: 06 July 2006
Cubicle Boy is right, AR 600-20 chapter 1-6 Military grade and rank, table 1-1 states what the form and address of each rank is. However there is no specification for face-to-face or phone. Best to stay formal.
Posts: 99 | Location: Baghdad | Registered: 01 November 2006