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): https://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.Best,
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