Back in 2012, Rep. Darrell Issa (R-Calif.), as part of his frequent investigations of the behavior within President Barack Obama's administration as the chairman of the House Oversight and Government Reform Committee, sent a letter directly asking then-Secretary of State Hillary Clinton if she or any other senior agency official at the State Department had used a personal email account to conduct business.

She never responded, according to story at the The New York Times:

Mr. Issa also asked Mrs. Clinton, "Does the agency require employees to certify on a periodic basis or at the end of their employment with the agency they have turned over any communications involving official business that they have sent or received using nonofficial accounts?" Mr. Issa's letter also sought written documentation of the department's policies for the use of personal email for government business. Mrs. Clinton left the State Department on Feb. 1, 2013, seven weeks after the letter was sent to her. When Mr. Issa received a response from the State Department on March 27, all he got was a description of the department's email policies. According to the letter, any employee using a personal account "should make it clear that his or her personal email is not being used for official business."

A Clinton aide is taking the "everybody who mattered already knew" argument as a response:

An aide to Mrs. Clinton said in a statement Tuesday that "her usage was widely known to the over 100 department and U.S. government colleagues she emailed, as her address was visible on every email she sent."

The relevant question (and what goes unanswered) was whether people outside the government knew she was using a non-governmental email address and whether those correspondences were hidden from public review. Also of note: Issa wasn't even targeting Clinton here. This was all a response to the discovery that staffers of the Environmental Protection Agency had been using their private or secret email accounts (and fake names) to conduct business in a way that allowed them to conceal correspondence from Freedom of Information Act requests.