Hi,
It looks like it’s some kind of email sample post type, probably related to buddypress or something. Maybe the ‘bp-email’ post type?
Make sure that those post types are not choosen to be returned (General Options -> Sources panel): http://i.imgur.com/3O7PSRC.png
Only choose post types you know, definitely not all of them. Many post types are only placeholders for plugins, not to be viewed.