Most of the peoples use Facebook in their mobiles. If u get access to anybody of your friends mobile,just open his already logged in Facebook account (people rarely logs out from phone!).
1. Gain access to friend's Facebook profile from mobile, obviously it must have internet connectivity.
2. Scroll down till you get list like "Events","Notifications" etc. From that list,click on "Photos".
4. Note down "Email Address" under "Post by email" section. (By using this mail you can update status, photos etc.).
(Click Here). It also works through pc.
6.Now suppose you got email address as "firstname.lastname@example.org".
7. Go to gmail,yahoo or any other email platform where you have signed up. (Here I have used Gmail).Click on "Compose".