On Monday, State Department officials confirmed that former Secretary of State Hillary Clinton exclusively used a personal e-mail address to conduct government business throughout her four-year stint at the State Department. Clinton's failure to use a government e-mail address "may have violated federal requirements that officials’ correspondence be retained as part of the agency’s record," according to The New York Times, which first broke the story.

It also may have removed the paper trail on which the public relies to make sense of the past. "Hillary Clinton's emails are the contemporary equivalent of letters and memos from past secretaries of state that have enabled historians to study the history of American foreign relations," Mary L. Dudziak, a professor at Emory Law School and a leading U.S. legal historian, wrote in an e-mail. "By failing to retain her correspondence at the time it was produced, Secretary Clinton may have jeopardized preservation of a full and accurate historical record. This undermines the ability of scholars to assess her own legacy as secretary. This is most unfortunate."

This isn't the first controversy over the use of private e-mail by public officials. "In 2007," as Josh Gerstein at Politico noted, "the Republican National Committee announced that a large volume of emails generated by 22 officials in President George W. Bush’s White House, including political adviser Karl Rove, had been deleted and were unavailable for congressional investigators."

News of the controversy spread quickly on Monday evening, igniting the wrath of pundits and inspiring criticism from potential 2016 presidential rivals and scorn from political commentators on social media. The scandal also follows a week of woes for the former secretary in which the Clinton Foundation came under scrutiny for accepting donations from foreign governments during Clinton's tenure as secretary of state.

As The Times reported, a Clinton spokesman, Nick Merrill pushed back against the furor over the disclosure, arguing that the secretary's use of a personal e-mail address conformed with the “letter and spirit of the rules.”

Current and former archives officials are among the many who don't seem to be buying it, especially given Clinton's exclusive use of a private account for all of her correspondence. In addition to potentially sullying Clinton's reputation ahead of a possible presidential run and complicating her legacy at the State Department, this development triggers a number of questions. What were the security risks of using her own e-mail domain? How did the Obama administration, which has continually touted its transparency, fail to stop a controversial practice over the course of four years? And why did Clinton aides fail to intervene, to ensure compliance with federal rules?