One, beyond the obvious stuff — like why did she do this and how did no one in a White House that’s bragged about its transparency not object — is just how widespread the practice is? Team Clinton is trying to take the sting out of the Times report, in part, by pointing to other public officials whose own commitment to the spirit of record-keeping laws has been less than rigorous. The comparisons are imperfect, to put it charitably, because the officials operated under different rules:

– Former Secretary of State Colin Powell used personal email to correspond with counterparts before the current federal regime was in force.

– Former Florida Gov. Jeb Bush (R-Fla.), a potential foe for Clinton in the 2016 presidential race also used personal email, but he was governed by looser state laws. He has since voluntarily released 275,000 of those messages, representing just a partial trove of his archive.

And to the extent the Clinton defensive strategy is to deflect attention elsewhere, it may be undone if she alone among top Obama officials past and present maneuvered around the rules for preserving records. So far, that appears to be the case. According to NBC, Attorney General Eric Holder, former Defense Secretary Chuck Hagel, and senior Obama adviser Valerie Jarrett all use their official email. To that list, Fortune can add Treasury Secretary Jack Lew. A Treasury spokesperson tells us in a statement that the department’s policy “is that employees should conduct official business through their official Treasury email accounts,” and Lew follows suit.

“The policy recognizes that there are situations in which an employee must use a personal email account for work purposes. In those circumstances, the employee must ensure that all federal records are preserved,” the Treasury statement continues. “Secretary Lew complies with Treasury’s policies regarding email use. Secretary Lew uses government email and conducts official Treasury business on government email.”

Lew’s compliance is particularly notable considering he served as a top lieutenant to Clinton at the State Department. After Obama won the presidency, Lew — President Bill Clinton’s one-time budget director — agreed to leave a plum Wall Street gig running Citigroup’s alternative-investment arm to help Clinton set up and manage her operation as the nation’s top diplomat. In fact, Clinton carved a new role for Lew by splitting the duties of her deputy into two jobs, a unique power-sharing arrangement by which another Clinton White House alum, James Steinberg, focused on foreign policy while Lew looked after State’s day-to-day functions. Officially the deputy secretary of State for resources and management, Lew worked in effect as the agency’s chief operations officer, presumably placing the decision over the Secretary’s email within his brief. But the Treasury spokesperson declined to comment on Lew’s knowledge of or involvement with Clinton’s email arrangement.