Was there any concern about national security and classified material on the part of Hillary Clinton when she was Secretary of State?

Wikileaks has released an email from Hillary Clinton’s private email account that appears to show close advisor Huma Abedin using it to reply to Hillary’s incoming messages.

“Let me know when we can talk,” State Department advisor Jake Sullivan wrote to Clinton in November 2010.

“Hey its huma,” Abedin apparently wrote back.

“She can’t talk right now

“She will call when she gets in car. What flight u on? Can u email me on other email?”

How often did Abedin utilize Clinton’s account and how much information intended only for a cabinet-level person did she consume?

And what does this mean if Clinton is in charge of protecting all of our national security secrets if she is the commander-in-chief?