Apparently you can foward a mail, but only through addons. But as someone mentioned earlier, and everyone being paranoid around here, it could possibly not be allowed because you cant do it through the normal game UI. But if that was the case, then Omen threat meter would not be allowed either, because I cant do that through the in game UI.

It all goes back to "KNOWING" what blizzard has/is intended to do with a specific mechanic. But since some people seem to be able to read blizzards minds around here, they seem to be able to know what blizzard meant when they do a certain thing, or if its going to be allowed or whatever.

Its prolly not meant to be, but i wouldnt hesitate to do it personally, god forbid if someone gets their panties in a bunch for doing it though.