Few days before, I shared the info that Facebook's Email Service is gonna launch soon. And now, Facebook's Email Service is launched officially. According to Facebook, its not an email service but a better messaging service. Facebook Message, Facebook's Email Service, is now available on invitation only> and you can get an invitation from the method given below.
You can ask for an invitation from the Facebook Messages Invitation Page. You can also invite other people when you are having the access to Facebook Messages. Also if your friends are having Facebook Message then, they can also invite you to use Facebook Message, Facebook's Email Service.