Mrs. Clinton is not the first government official — or first secretary of state — to use a personal email account on which to conduct official business.
But her exclusive use of her private email, for all of her work, appears unusual, Mr. Baron said. The use of private email accounts is supposed to be limited to emergencies, experts said, such as when an agency’s computer server is not working.
“I can recall no instance in my time at the National Archives when a high-ranking official at an executive branch agency solely used a personal email account for the transaction of government business,” said Mr. Baron, who worked at the agency from 2000 to 2013.
via Hillary Clinton Used Personal Email at State Dept., Possibly Breaking Rules – NYTimes.com.