I normally signup to newsletters with my Fastmail account that I then move into a “newsletter” folder. There’s a rule then that sends a copy to my Newsblur email so that I can read them there.
It used to work for all the newsletters, but recently (don’t know exactly when), one of the newsletters arrives in Newsblur without the content (see screenshots below).
If this is what I’m famliar with, it’s more that the email newsletter provider having very aggressive CSS styling for their posts, which do not play nicely with how NewsBlur embeds the content. eg.: the newsletter hard-specifies “white” text on a dark background, but NewsBlur allows the “white” text but forces a “white” background, making the text unreadable.
Try switching between the “Original”, “Feed”, “Text”, and “Story” views to see if any of them are suitable. Also, I’ve found that just using C-a in the browser to select all text can help normalize the text-vs-background contrast to make things readable, if annoying.
Sadly it doesn’t seem to be a problem of styling or CSS. I tried switching between the different views as you suggested and when doing so I opened the developer tools to inspect the content of the page and the text of the email is just not there.