Following the creation of your Facebook account, you'll be granted with a Facebook email address of this type firstname.lastname@example.org. Your Facebook email address is an easy target for spammers as it can be easily guessed (a combination of your public username and the @facebook.com domain). Messages and notifications sent to your Facebook email address are automatically forwarded to your primary email address.
This quick guide will teach you how to disable your Facebook email address in a couple of easy steps.
How To Disable Your Facebook Email Address
Sign in to Facebook and go to Settings:
Go to General settings and click on Edit located next to the Email field. Clear the Use your Facebook email address checkbox: