We had a bit of a discussion here a while back about the mail and how important it would be in preventing desertion. I tried to address the subject a bit in my essay too but I'm not really confident that I have the answers so I didn't go into much detail.
I think the Mil/CivGov schism would make a national/international mail service more difficult to resurrect. But I risk another thread-jacking with this.
EDIT: Found it!
http://forum.juhlin.com/showthread.php?t=790