Such is the challenge of hosting public content. .rackcdn.com is for content hosted on Rackspace Cloud Files and served via our partnership with Akamai.

Cisco's SenderBase recently changed the rating for .rackcdn.com and Bad Things (tm) happened. We (Rackspace) have been in contact with Cisco, and our reputation with their products has been restored (see http://www.senderbase.org/senderbase_queries/detaildomain?se...). Unfortunately, this probably won't be fixed for you until your security filters update the policies from senderbase itself.

Let me know if you have any other issues with this. john.dickinson@rackspace.com