I have not found anything relating to messages on the forum so here is a suggestion.
make the message window about the size of "play with a group" window and have it refresh on a regular basis.
Reason:- If you are waiting for an answer, you have to refresh the screen manually otherwise you won't know someone has answered. The current window is very small and does change colour but has a bar above it the same colour. This sometimes is not noticed if you are concentrating on something else on the page. A flashing message window would be even nicer.
When trying to set up multi-player games in CC's over a few time zones a quick reponse from the recipient would make things easier and if the window popped up, even while you were playing, you can answer it and continue on with your game