I've never maxed my inbox out, but I assume there is no message that notifies the person that their inbox is full. There should be a warning implemented to notify the user that they can't receive PMs until they make space.
If this function exist, I apologize and feel free to disregard this thread. Hell, just delete it.
If this function exist, I apologize and feel free to disregard this thread. Hell, just delete it.