From the group of 30,000 e-mails returned to the State Department, 110 e-mails in 52 e-mail chains have been determined by the owning agency to contain classified information at the time they were sent or received.
Eight of those chains contained information that was Top Secret at the time they were sent; 36 chains contained Secret information at the time; and eight contained Confidential information, which is the lowest level of classification. Separate from those, about 2,000 additional e-mails were “up-classified” to make them Confidential; the information in those had not been classified at the time the e-mails were sent.,,,,
...None of these e-mails should have been on any kind of unclassified system, but their presence is especially concerning because all of these e-mails were housed on unclassified personal servers not even supported by full-time security staff, like those found at Departments and Agencies of the U.S. Government—or even with a commercial service like Gmail.....
Separately, it is important to say something about the marking of classified information. Only a very small number of the e-mails containing classified information bore markings indicating the presence of classified information. But even if information is not marked “classified” in an e-mail, participants who know or should know that the subject matter is classified are still obligated to protect it....
....James Comey