How do you do a reverse email look up to identify the sender?

These days it's Facebook that's the best way to identify the sender of a (valid) email address. Facebook has over 450 million users worldwide and it allows you to search via email. Here's how you do it:

a) Log-in to Facebook. You can't search by email unless you're logged in.

b) In the search box on the top, type the email address.

c) If a person with that email is registered on Facebook, you should be able to see his first/last name. Now, add him as a friend :D