From the story by Keith Koffler here:
“This is gigantic,” said [Joseph] diGenova. “She caused to be removed a classified marking and then had it transmitted in an unencrypted manner. That is a felony. The removal of the classified marking is a federal crime. It is the same thing to order someone to do it as if she had done it herself.” On the June 17, 2011, email chain with senior State Department adviser Jake Sullivan, Clinton apparently asked Sullivan to change the marking on classified information so that it is no longer flagged as classified. ... The revelation also appears to put to the lie Clinton’s claim that she never handled classified information on her server.