Learn to read.
Not once does it say "there will be email in the game"
It says he HAS been receiving email, it doesn't say you will use email in the game, it doesn't say you recieve email in the game, it doesn't say you send email im the game, it says Niko HAS been recieving emails - which is the reason for him moving to Liberty - why would his cousin send him emails while they were both in Liberty, telling him to move to Liberty?
Try some common sense.