Idea! -You've got mail.

[Ben]

Only i agree on the problems and think this will be very hard and some players might never care to check their mail.

but then thats their problem.
You would have to put limits on it imo. Like 10 messages in your mailbox is allowed, or you can only send one every hour or something.

but in general i love this idea, and i think it would be better if  only people with their own houses could do it. That would also encourage people to donate!