Marking emails is kind of tricky. One is SUPPOSED to put a max classification string in text in the subject, then above, and below the full text if I remember correctly. It is not like the only things marked with the classification are attachments that have something like a stamp, pulled from some document storage.Of course, but when dealing with the Clinton's one must parse words carefully.
I have never received a document marked "Classified." I have received (on authorized systems) lots of classified documents.
Let's just say she is as completely clueless as she wants us to believe. If that is the case there are a instances where someone is guilty of not marking the messages properly, mishandling classified information. She is throwing them under the bus.