by nippersean on Tue Jan 12, 2010 12:12 pm
It's not legal. Game chat only.
I've copied and pasted rule #2 below you can find them under the "rules" tab at the top of the page.
Rule #2: No secret diplomacy
Any form of diplomatic discussion between opponents must be posted in the game chat in English or in a language that all opponents understand. Diplomacy includes, but is not limited to: proposing truces, negotiating alliances, and coordinating assaults. Secret diplomacy can be hard to prove, but if you suspect it you should leave the players in question appropriate ratings. If you feel certain about players engaging in secret diplomacy consider reporting them in the Cheating & Abuse Reports forum by posting a new topic.