If you are a Facebook member, check out your profile – you will see that your main e-mail which publicly shows to everyone is now..@Facebook.com, and all the other services are hidden. That occurs even if you didn’t have a Facebook e-mail account before – it has been generated for you automatically.
Facebook launched their own e-mail service back in 2010, but it hasn’t really gained popularity among the users. In April the same year the company synchronised e-mail accounts with timeline so that the user.name@_facebook.com would always match with URL of the personal page of the facebook.com/name.user.
However, the e-mail publicly shown to everyone, can be returned to the one selected earlier in the profile settings at any time.