Hi Garyn,
The basic idea is to achieve a workflow, with firstly a Query activity then (or directly) a Javascript queryDef for selecting the expected deliveries and getting the html content and the all the content type you manages (facebook, line, pdf, MMS, in which URL images can exist). Normally raw text and SMS are not concerned.
The expected deliveries can be all deliveries or the ones expected such as the one being edited, the model deliveries, keeping the completed deliveries as is, for far easier stuff.
So in the queryDef Javascript activity node contains at least the html content.
<node expr="[content/html/source]" alias="@contentHtml"/>
In the result query loop, manage the result.@contentHtml for substring/replace string based on img element type of the DOM and src change of subdomain1 by subdomain2 (Javascript methods).
Then for each delivery item, save the entity delivery (or do it in a whole with an array for contentHtml new values and a writeCollection API call, at the end).
But it is not enough, except if deliveries are in editing mode or are templates models.
Otherwise, if the deliveries have been sent or images published.
So not only the html must be changed but also images uploaded on the new server, right ? Or does Adobe team do the move for you?
Also take care of the delivery uploadImages parameter, if set, it overloads the default nms:option for image resources location (see the Deployment wizard for your value).
Regards
J-Serge