This seems useless to me. The game only checks for new messages on first startup. The user will immediately see this, and a sound is unnecessary.
Even if we had the game check for new messages more often, it would only be checking when the user is doing some action, and they will still see the new message notification immediately.
TPT isn't a chat system you leave idle in the background. You don't need sounds or notifications when you get a new message.
Maybe,but I am often waiting for a message that is important to me and this would allow you to do something other and not bore.
Have a good day!
BokkaB