I have to imagine that AOL & Hotmail were doing it because the emails appeared to work as spam, but it's still intriguing to see an organization have its apparently legitimate email blocked by AOL and Hotmail.

Further, the Microsoft-Hotmail administrators inform us that they are blocking our communications to Truthout subscribers on their systems due to what they describe as our "reputation."
2.) It is becoming increasingly apparent that the Free Email Services - all of them - are a morass. You are a commodity to these administrators and as far as they are concerned your rights are your problem, not theirs. If you are serious about receiving TO, or any other content they are not supportive of, you are pretty much on your own. Bluntly stated: AOL, Microsoft, Yahoo and all of the domains they control restrict what you receive in your inbox. And it is at their discretion, not yours.

(emph mine)

To start, I haven't read enough about this -- even all of what's on the page -- to see how this now well over a year old spam battle got started. I don't know what sorts of emails truthout.org sends. I wonder if the email is originating at a server that was flagged as bad news.

So the lessons seem to be that spam may be used for legitimate purposes and that automated safety checks against spam have so much momentum that making exceptions are, well, exceptionally difficult within the cultural structures of their human administrators-managers.