During the beginning era of Facebook, all newly registered users have to use the email method to verify their Facebook account. Now, it turns out to be Facebook has already removed this verification method during the users sign up process. However, recently, it seems more than 1.5 million emails have uploaded to Facebook through the email verification method.
As for now, Facebook clarifies that all the emails are not shared with anyone else. At the same time, Facebook says its already starting the process to delete all the emails. If your emails are on the list then you should receive a notification from Facebook.
This was first noticed by the security breacher where it shows a prompt screen to users to enter the password for their email during the signup process. After entering the password, a popup message box will show “importing” without showing any permission to accept. The main purpose Facebook creates this feature is to let its users build their social connections and also recommend friends based on the email address.