Keith, I usually agree with you, but not in this case. This suggested 
content-type DOES describe the content type: it IS a zip-compressed file 
that's enclosed there. It just happens that you also know what was 
compressed.
        Tony Hansen
        tony(_at_)att(_dot_)com
Keith Moore wrote:
So, I suggested:
content-type: application/x-zip-compressed; encapsulates=application/pdf
sorry, this is just unacceptable.  there are too many things (e.g. mail 
filters) that expect the content-type to actually describe the content.