Well, another option is that some emails SHOULD have had those markings before they were sent from or to her.
I strongly believe that the professional originator of the material DID mark it properly, but that those markings were removed by a Hillary staffer before re-transmittal to her unsecured server. As SecState, neither she nor her staff members had the authority to remove the classifications determined by the originator, which may have revealed “means and methods”.
Based on personal experience, the technical personnel who generated the data DID mark it appropriately. Therefore, one or more of Hillary’s staff members are guilty of removing the identifying marks.