Using webhook to push blog images and urls into an email

Sure, you can pull whatever you want in via a webhook.  Trigger the webhook on Filled Out Form, trigger the email on Change Data Value to the field you're using to receive the response.

You'd want to use a Textarea field no matter what, but the question is going to be whether you pull the feed data in as a raw feed and then #foreach over it and format the output using a Velocity script (gives you more control of formatting within Marketo) or supply the feed data as prefab HTML.

Also, you won't be feeding the raw XML/HTML response into the webhook. This won't work because Marketo will never gulp the entire XML text into a field. You want to encapsulate the XML/HTML response in a JSON string property. So the transport is JSON, the inner content is XML/HTML.

I've never done this before, but if I were to try I think that - assuming these blogs are not being selectively chosen based on data that is unique to the lead - I would prefer to use the REST API to periodically refresh the values of program My Tokens: http://developers.marketo.com/rest-api/assets/tokens/#create_and_update

http://developers.marketo.com/rest-api/assets/tokens/#create_and_update

I think that would be a simpler, more reliable process, and easier to QA (you can just send yourself a sample email or use the preview, rather than testing with lead records which have to trigger a webhook individually).