Classification is Inherent not Marked
The classification of a document is inherent in the document based on the contents. Classification MARKINGS aren't dispositive. Many of Hillary's emails were not MARKED as classified but WERE classified based on the content. The creator of the document is REQUIRED TO apply appropriate classification markings such as "Secret" "Top Secret" or "NOFORN" or "CANUKUS EYES ONLY" and failure to apply the appropriate marking is an ADDITIONAL crime.