Mills was Clinton’s chief of staff when Clinton was secretary of state and since then has been one of Clinton’s lawyers. The date and most details of the interview will remain secret until it’s mentioned in a September 2016 FBI report.
The FBI shows Mills seven emails that she forwarded to Clinton which contain information later determined to be classified. Acccording to the FBI, although “Mills did not specifically remember any of the emails, she stated that there was nothing in them that concerned her regarding their transmission on an unclassified email system. Mills also stated that she was not concerned about her decision to forward certain of these emails to Clinton.”
Apparently, some of the emails reviewed by Mills are classified at the “top secret/Special Access Program” (TP/SAP) level. Because the FBI will mention that while “reviewing emails related to the SAP referenced above, Mills explained that some of the emails were designed to inform State [Department] officials of media reports concerning the subject matter and that the information in the emails merely confirmed what the public already knew. (Federal Bureau of Investigation, 9/2/2016)