Stealing this idea from Stackoverflow.
I think a lot of players might interact a little bit more if they were aware of how long it's been since they last wrote something. A lot of times, people think they do things far more often than they actually do.
Therefore, set a "message time threshhold" for talking to the whole realm, talking to your knights (if a lord), talking to the realm if you are in govt. but with slightly different message.
When a player checks his messages, if he has passed the "threshhold", an overlay message saying something like:
"Battlemaster is an interactive roleplaying game, and we count on the players to interact to keep it fun for everyone. You haven't written to anyone in X days - perhaps take a moment to write something?"
No penalties or other effects, merely a nag screen reminding people that the game needs them to make it fun. I would let considerable time pass before this jumps out - a month would not be too long, IMO.
I think Lords & Dukes should get this a little more frequently, and govt. officials more frequent still, with wording that they've taken a position of importance in the game and it is expected of they will give more back to it than the average player.
Since there is no actual penalty, I don't see any issue with Inalienable Rights.
