In case someone needs this in the future here is the answer to my own question.
To use RSS in email you will have to first submit a support ticket to enable the CA feature for external content.
The help guide for the set-up is in Chapter 4 of the RPL Reference Guide: “XML Processing” (Starts on Page 94), and they assign the path to the RSS feed (which should be/needs to be an XML document). Then you would need to code HTML documents to parse and display the correct content from the Blog. The guide will point you in the right direction.
The guide can be found in RI:
Responsys Help > Guides and Best Practices > RPL Reference Guide