This inbox contains messages sent from within Facebook, as well as messages sent to the unique Facebook.com email address containing that user’s vanity username. You can send an email to Facebook by following a few steps.
– Sign into your Gmail account at Gmail.com.
– Click the “Compose Mail” button on the left side of the screen.
– Enter the vanity username for the Facebook user you’d like to email, followed by @facebook.com. For example: email@example.com
– Click the “Send” button to send your message. Your email will show up in the recipient’s Facebook messaging section as a new message, and a small envelope icon will let them know that the message was sent from an email address.