The nose light is for messages from the nabaztag.com website, not email messages. The fact it flashes regardless of you actually having messages is a current bug. It didn't used to flash all the time.

They do need to provide more info about the tummy lights though. Most of them you learn after a while of having a Nabaztag. The current server issues aren't useful though in providing a consistent experience. Lots of people get thrown by the air quality tummy lights having turned on that service by accident or out of curiosity without realizing it leaves the tummy lights flashing all the time.

Bugs aside, the somewhat random behaviour is quite endearing. More random happenings alongside a consistent service for the services that need to be consistent is fine by me.