Most Awake that tend not to leave safe territories also tend to either dislike phones or simply not bother with them, seeing them as a tie to the Outside world, and often a way they can be tracked -- though all Sanctuaries and many safe territories have methods to prevent anyone from tracing phone signals, messages or listening in on phone calls. This makes communication between the Awake sometimes somewhat difficult, making Messengers necessary so that Awake who are busy can still get urgent messages to others. The majority of Messengers stay within their own territories, but those of higher ranking venture into Outside territories.
Blue Bunny: The first rank among messengers, Blue Bunnies only travel within their area. This is the entry-level ranking, and while many messengers choose to stay Blue Bunnies so that they can stay not only safe but often with their families, no one can move on to other rankings without excelling as a Blue Bunny first. Blue Bunny messengers have no age requirement in most areas -- if they are old enough to find their way around, they're old enough to become messengers.
Black Pigeon: The middle rank of messengers, Black Pigeons live largely nomadic lives, always traveling in order to deliver their messages. To become a Black Pigeon, a messenger must have at least some ability to fight or a fail-proof method of escape -- the ability to fight is more common -- as they can often end up in dangerous situations even if they do not tend to go to dangerous areas.
White Rabbit: The highest rank among messengers, only the most elite make it among this rank. This is the most selective rank in that, though anyone can nominate a messenger to become a White Rabbit messenger, only Alice Row has the authority to promote a messenger to this rank. White Rabbit messengers are the only messengers who can travel between worlds, and some of the only people in the worlds who can do so without an airship or looking glass to do it. White Rabbit messengers are gifted with an ability called "dig", which allows them to create a portal -- a rabbit hole -- to any world that Alice Row has a treaty with.