The personal email address that Hillary Clinton used exclusively during her time as Secretary of State wasn't your typical Gmail, Hotmail, or Yahoo account. Instead, Clinton operated her own email server traced to an internet service registered to the Clinton residence in Chappequa, New York, according to the Associated Press. The report does not say where the server itself was based. Clinton did not use an email address issued by the State Department while in office, which would have made it far simpler for the federal government to retain copies of her messages as is required under the Federal Records Act.

Nor did Clinton use a personal Gmail or Microsoft account to conduct official state business, a move that's occasionally landed other US lawmakers in hot water. But even in those instances, politicians rarely use private accounts exclusively. With Clinton, everything went through her own private internet service, which in itself is sure to raise questions about how secure the email system was. How did encryption and other security mechanisms compare to what's offered by Google, Microsoft, or the federal government?

In 2012, Clinton's email was reconfigured to use Google as a back end if the self-managed email system went down, the AP reported. (Just one year prior, Google publicly accused China of trying to hack into personal Gmail accounts belonging to senior members of US government, journalists, and other users.) Google was later replaced by MX Logic, an email provider that's now under McAfee.

Clinton exclusively used the email address — hdr22@clintonemail.com — through the four years she served as state secretary under President Obama. During her tenure, "aides took no actions to have her personal emails preserved on department servers," The New York Times said Monday. But two months ago, Clinton's team gave 55,000 pages worth of emails to the State Department. It is unclear how advisors curated her inbox to decide which emails would be forwarded to the National Archives and which would not. A Clinton spokesperson said that because she so often corresponded with other federal officials through their government-provided accounts, Clinton had "every expectation they would be retained" for future reference.

Colin Powell, who served as Secretary of State under George W. Bush, used a personal email account in his communications with top officials both in the US and internationally. At that time, regulations around email preservation were much looser. Clinton's direct predecessor, Condoleezza Rice, rarely used email while holding the office. In the event she did, Rice used her government account. Current Secretary of State John Kerry similarly uses a government email address, ensuring his messages will be kept permanently. Clinton has not yet publicly discussed the issue or explained why a top-level cabinet member should be permitted to go it alone with a private email address. The State Department hasn't indicated that it's missing any emails from Clinton's tenure, but if not all of them have been handed over, requests to recover them in the future could run into Clinton's lawyers.