Here's how to change it back:
- Click About on your profile and find your email address. Click Edit.
- Click on the circle next to your @Facebook.com email address and change the setting to Hidden From Timeline.
- Click on the circle next to your other email addresses and change the setting to Shown On Timeline.
- Click the Save button at the bottom of the Edit popup.
Facebook launched this awful email service in 2010, which would send the messages to your Facebook messages area. It sucks though because I had this awesome Twitter account I registered with that email address and forgot the password, and no matter how many times I sent the password reset email it never arrived in my Facebook inbox, and that's why I hate it so much.
Now I have a reason to hate it even more.