Some newsletters forwarded into NewsBlur seems to have their formatting altered, to the point where they become un-readable. Quite common is images out of alignment so that a picture made of multiple separate images (a common trick to get clickable regions) don’t fit together properly; or text colour lost so that the email appears empty (screenshots below, highlighting the content shows the ‘hidden’ text).
These emails appear fine in Gmail (Chrome, macOS) and Apple Mail, so it looks to be something that is changing within NewsBlur.
From the original announcement, you mention making sure that newsletters display well on desktop and mobile, so I wonder if there’s something you’re doing there. But to be fair, the better email marketers out there should be sending emails with responsive designs already!