Extra, every bank employee has to take a class annually. In this class you learn the difference between public, non-public, restricted, and confidential information as it pertains to you customers. You have to know how to handle each type of information and what you can, and can not, do with it. Additionally, being extremely weary of cyber crime, the sending of confidential information through a non secure transmission is prohibited and grounds for disciplinary action, up to and including termination.
The thing is that none of the documents are marked in any way. It's the bank employee's responsibility to understand the different types on information and then to handle them accordingly. This is what makes your whole "wasn't marked" comments pointless. Email communication can, and often is, the start point of a conversation. It has been seen by no one who could make it anything until after it is sent of received. If the sender does not mark it as classified before it is sent, then all marking is nothing by post event clarification.
As an example, Hillary receives an email on her personal email server from the Middle East that says, "per your instructions I have reached out to so and so leader of so and so forces in Syria. He believes that your proposal is promising and would recommend an August 10th target date for the offensive."
That is classified information as it indicates that the U.S. SOS had requested information be given to a foreign leader, made a proposal, and included a possible date for military action. If the sender had not sent this marked as classified and Hillary received it and then forwarded it on to the Pentagon, she received and sent classified information on her server. Anyone with a brain, and especially someone with 30 years of government experience, knows this type of information is classified, just like every bank teller knows a SS number is confidential. The fact that it was not marked when received or sent is unimportant and merely an excuse.
