Washington (AFP) - Questions keep swirling about the electronic correspondence of Democratic presidential hopeful Hillary Clinton, whose use of a private email account while secretary of state has dogged her on the campaign trail.

In the latest development, Clinton has agreed to turn over her private server to the Federal Bureau of Investigation, after months of refusal.

Here is what is known -- and unknown -- about the emails and the controversy that has lingered.





- The basics -





Clinton sent and received a total of 62,320 emails during her 2009-2013 stint as top diplomat, to and from a private account that she said she used out of "convenience" in lieu of an official government email address.

At the State Department's request, she turned over what she has described as all of her official emails -- 30,490, to be exact.

Clinton said the remaining 31,830 are personal records, and that her server was wiped clean after she provided paper copies of her official communications.

The State Department is working its way through the official emails. It has already released 3,500 of them publicly, on a monthly schedule, with the intent of releasing the entirety of the tranche by January 2016.





- Classified? -





"I am confident that I never sent or received any information that was classified at the time it was sent and received," Clinton told reporters on July 25.

But investigators recently said they found four emails that contained classified material.

On Tuesday, the intelligence community's inspector general, Charles McCullough, informed Congress that two of those emails contained "Top Secret" information.

The State Department insists that none of Clinton's emails were classified at the time but a later review resulted in some being placed in that category.

There may well be more classified data, as the emails were merely part of a sample of the 30,000 records provided to authorities.





- Investigation -





The New York Times reported in July that inspectors asked the Justice Department to open a "criminal referral" into the matter.

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It corrected itself to label it a "security referral," but that did not stop Clinton's Republican rivals on the campaign trail from piling on about Clinton's potential criminal activity.

In a lengthy explanatory email, Clinton's communications director Jennifer Palmieri insisted "there is absolutely no criminal inquiry into Hillary's email or email server."

The FBI is investigating not Clinton herself, but the security of the emails.





- Email revelations -





The 3,577 Clinton emails released to date offer a glimpse into the operations of a large Clinton machinery.

Much of the email traffic addresses mundane personnel matters or the forwarding of various press reports.

Several pages of the documents were heavily redacted.

Among the biggest revelations is that longtime Clinton confidante and friend Sidney Blumenthal was routinely advising the secretary of state, on matters including Libya, despite not having an official government role.

Fewer than 10 percent of the emails relate to Benghazi or to Clinton's response to the September 11, 2012 terrorist attack that killed four Americans there, including the ambassador.

A batch of 300 Benghazi-related emails was publicly released in May after they were provided to a congressional committee investigating the terror attack.

They reveal little overt concern about then-United Nations envoy Susan Rice's depiction of the attack as a "spontaneous" response to an anti-Muslim video.

But one April 24, 2011 email from senior Clinton aide Huma Abedin warned Clinton of "new local reporting that hotels are being targeted" in Benghazi.





- Hacked? -





Wisconsin Governor Scott Walker said in last week's Republican presidential debate that snooping Chinese and Russians might know more about Clinton's emails than members of Congress.

"And that has put our national security at risk."

Not so, insisted Team Clinton, which said there is "no evidence there was ever a breach" of security with her email account or server.



