In the In-Game Rules and Policies, Official Correspondence, you say [emphasis added],
"We ask that you do not post, broadcast or reproduce in-game, without express written permission, any private correspondence between official representatives of [FLS] ..."
Suggest that you replace "We ask that you do not" with "You may not". "We ask" implies a request that need not be followed. If you want to be able to sanction such postings, the mandatory language "You may not" provides a much clearer basis for player expectations that such conduct is sanctionable.
You DO make this explicitly forbidden in the website rules -- I suggest that the Game Rules and Policies, Official Correspondence section be consistent with it. Doing so will help avoid confusion.