Well, this might be the explanation: The new regs apparently weren’t fully implemented by State until a year and half after Clinton left State. Here’s the timeline: Clinton left the State Department on February 1, 2013. Back in 2011, President Obama had signed a memorandum directing the update of federal records management. But the National Archives and Records Administration (NARA) didn’t issue the relevant guidance, declaring that email records of senior government officials are permanent federal records, until August 2013. Then, in September 2013, NARA issued guidance on personal email use.
A senior State Department official emailed me to say that “in October 2014, a Department-wide notice was sent out which explained each employee’s responsibilities for records management. Consistent with 2013 NARA guidance, it included instructions that generally employees should not use personal email for the transaction of government business, but that in the very limited circumstances when it is necessary, all records must be forwarded to a government account or otherwise preserved in the Department’s electronic records systems.”