I had an issue where a user had an email in the Core system, but under the user's settings it says "None" where the email is. When I go to add one it was grayed out. It seems that if the user has the email access profile field set to no, the notifications settings page will show an email address of "none available" even if they user has an email in the system. If users are allowed to modify their notification settings then e-mail either needs to be accessible here (both viewable and editable) or this email address needs to be separate from the one in the system.