Wrapping MIME Objects: Application/MIME
MIME is a general-purpose mechanism for labeling and aggregating objects into complex hierarchies. Some MIME objects are discrete objects. If placed within another MIME hierarchy, they need to appear as a leaf node in the containing hierarchy, rather than seeming to be continuations of that hierarchy. This specification defines Content-type Application/MIME to provide an encapsulation mechanism for arbitrary MIME structures. This facilitates their treatment as a single unit, rather than causing them to be treated as part of any containing MIME hierarchy.