What about TuxMail?!
What does this mean? Every now and then ThunderBird will deliver our post to a mail box in the Overworld. This mail contains things such as "You've completed this challange!" or "Nolok's getting hungry!". When internet multiplayer comes along this could also be used to communicate and to set up races as well.
The messages would be sent by the game itself so it wouldn't need internet connection and it wouldn't phone home. It would just have a repo of messages and use them now and then. You could also use it for notices from stkaddons.net!