Hillary Clinton's exclusive use of a non-government email account to send messages to her staff during her time as Secretary of State is a break from what other top officials have done, raising concerns from both Democrats and Republicans about the propriety of the practice.
Aides to former Secretary of State Condoleezza Rice and former President George W. Bush said neither official routinely sent e-mails to staffers while they held those posts. Rice "did not use her personal e-mail for official communication as Secretary" and instead exclusively used her State Department account, according to a top aide who did not want to be quoted publicly.
Attorney General Eric Holder regularly uses his government account, according to spokesman Brian Fallon, as does Valerie Jarrett, one of President Barack Obama's top advisers.
As Clinton aides have noted, Colin Powell did regularly use a personal e-mail account while Secretary of State.
A Powell aide confirmed that information, saying, "General Powell used a personal email account during his tenure as Secretary of State. He was not aware of any restrictions nor does he recall being made aware of any over the four years he served at State."
Other former office holders rarely used email accounts – personal or official – at all during their tenure.
"President Bush never used email in the White House. We only ever spoke on the phone or in person, or through memos, of course. I think it was the same at the Treasury Department, too. I never emailed with any of the three secretaries I worked with," said Tony Fratto, a former Deputy White House Press Secretary in the George W. Bush administration. Fratto is supporting Jeb Bush's 2016 presidential run.
"Everyone in government is wary of email," he added. "I'm surprised that Secretary Clinton used a personal account. I'm surprised she used email at all, to be honest. It's so hard to keep it secure."
Steve Clemons, a foreign policy expert at The Atlantic, said he has "never dealt with anyone at the highest levels of government who didn't have an official email address."
"The issue of disclosure here is that private email addresses are easily penetrated. The issue here is not so much that she had a private email address, but rather how much the Chinese and Russians got from her private email address conversations, as they no doubt were tracking her," Clemons added.
Clinton aides have not indicated why exactly the former Secretary of State did not use a State Department e-mail address. It's not clear what e-mail system she used, or if it was more or less secure than those run by the government.
"There is shock at what Secretary Clinton did because the most likely explanation of her intent seems clear — she created a system designed to avoid accountability, potentially in violation of the law," said John Wonderlich, policy director of the non-partisan Sunlight Foundation.
A story in the New York Times, published Monday, described how Clinton had "exclusively" used a personal e-mail account during her four years as Secretary of State.
Generally, letters and e-mails written by federal officials in their official positions are conducted on government accounts. They are archived and can sometimes be accessed by congressional committees or the public.
The disclosure about Clinton's emails, in fact, comes as the House of Representatives is investigating the attack on the U.S diplomatic outpost in Benghazi, Libya in 2012, while Clinton was still secretary of state. Clinton has released thousands of pages of her e-mails from this account to the State Department.
"Like Secretaries of State before her, she used her own email account when engaging with any Department officials," said Nick Merrill, a Clinton spokesman, in a statement. "For government business, she emailed them on their Department accounts, with every expectation they would be retained. When the Department asked former Secretaries last year for help ensuring their emails were in fact retained, we immediately said yes."
He added, "Both the letter and spirit of the rules permitted State Department officials to use non-government email, as long as appropriate records were preserved. As a result of State's request for our help to make sure they in fact were, that is what happened here."
White House officials also defended Clinton, arguing she was making her e-mails accessible. At the same time, White House Press Secretary Josh Earnest noted in a press briefing on Tuesday that "very specific guidance has been given to agencies all across the government, which is specifically that employees in the Obama administration should use their official e-mail accounts when they're conducting official government business."
For Clinton, who is expected to officially start her presidential campaign in the next few months, the email disclosure could be a political blow, although she remains the overwhelming favorite to win the Democratic presidential nomination. Republicans, including GOP contender Jeb Bush, have sharply attacked Clinton about the controversy, arguing that her use of a personal email account was an intentional move to obscure her communications.
And a prominent Democrat, former White House Press Secretary Robert Gibbs, said Tuesday that Clinton's use of the account is "highly unusual."
"I think it's something they're going to have to explain in good measure today and probably figure out how to get a lot of those emails, or as many as they can back into the archive," he said on NBC's TODAY Show.