Hillary Clinton’s private e-mail address that she used while secretary of state reinforces everything people don’t like about her, argues The Post’s Chris Cillizza, and is very dangerous to her presidential ambitions. (The Washington Post)

Hillary Clinton’s decision to use a private e-mail address exclusively — and set up her own server at her house to do so — during her time as the nation’s leading diplomat has dominated news coverage for a week.

Yet for all the great reporting that has been done, there are lots of questions that remain unanswered, either by journalists looking into the matter or, much less likely, by Clinton herself.

I put my head together with a few other reporters on The Washington Post’s national politics staff — Roz Helderman and others — to brainstorm a list of questions that Clinton and her team either haven’t answered entirely or at all.

1. Why did Clinton set up this e-mail system?

This is the biggie. Other secretaries of state — Colin Powell! — have maintained a private e-mail address, but no one has used such a setup exclusively. So why did Clinton, particularly given that she had to know that it might become an issue if or when she ran for president in 2016? (No, Clinton probably wasn’t thinking about 2016 at the start of 2009, but by the middle of her term, it was quite clear that another run for president was a real possibility.)

In a tense exchange with reporters, State Department deputy spokeswoman Marie Harf denied anything inappropriate occurred after revelations that former secretary of state Hillary Clinton used a private e-mail account for work. (C-SPAN)

Did she simply want to have as much control over her e-mail correspondence as possible? If so, why? Was there any political motivation in her decision, perhaps to shield some of her communication from Republicans? Did she consider a private e-mail server more secure from hacking than the government one? If so, who advised her on this?

Those are questions no one but Clinton can answer. But it’s not clear she has any plans to do so.

2. How many e-mails did Clinton send from her private account during her four years at the State Department?

Clinton World has shipped 55,000 pages of e-mails to the State Department. That much we know. What we don’t know is how many more pages of e-mails exist. Here’s what we do know, from a Post report Thursday:

“Of the e-mails that were turned over to State, the Clinton aide said, 90 percent were correspondence between Clinton and agency employees using their regular government e-mail accounts, which end in state.gov.

“The remaining 10 percent were communications between Clinton and other government officials, including some at the White House, along with an unknown number of people ‘not on a government server,’ the aide said.”

That doesn’t, of course, answer the more basic question: Is 55,000 the entirety of the e-mails Clinton sent? Half? A third? Obviously, if it’s 95 percent, that’s something very different from if it’s 35 percent.

Hillary Clinton caused controversy after reports revealed she used a private e-mail account during her time as secretary of state. Late-night hosts Jon Stewart, Seth Meyers and Jimmy Fallon couldn’t resist a few jokes at her expense. (Julie Percha/The Washington Post)

3. What did Clinton mean with her tweet?

On Wednesday night, Clinton tweeted this: “I want the public to see my e-mail. I asked State to release them. They said they will review them for release as soon as possible.”

But did she mean that she wants the State Department to release the 55,000 pages she sent the department? Or all of her e-mails? If it’s the latter, the burden of releasing them rests with Clinton, not the State Department. And, to reiterate Question No. 2, just how many of the e-mails she sent does the State Department not have?

4. Who was in charge of deciding which e-mails Clinton sent to the State Department for archiving?

What we know is that someone (or some people) in Clinton’s orbit went through the e-mails to decide which ones should be shipped to the State Department. The supposed standard for withholding e-mails was that they were “personal.” But, without knowing who was in charge of this selection process and what criteria they used to decide what constituted a personal e-mail, it’s impossible to get to the bottom of what the State Department has or, more importantly, should have.

5. Did anyone at the State Department or the White House raise concerns about Clinton’s exclusive use of the private e-mail system?

This is from Edward-Isaac Dovere’s article at Politico on Friday:

“The White House, State Department and Hillary Clinton’s personal office knew in August that House Republicans had received information showing that the former secretary of state conducted official government business through her private e-mail account — and Clinton’s staff made the decision to keep quiet.

“Sources familiar with the discussions say key people in the Obama administration and on Clinton’s staff were aware that the revelation could be explosive for the all-but-announced candidate for president. But those involved deferred to Clinton’s aides, and they decided not to respond.”

The larger question is did anyone — at the State Department or the White House — raise a red flag earlier about her e-mail being a problem before it became clear that this information had fallen into the hands of Republican congressional investigators?

If someone did, what was Clinton’s response? Or did the matter never get all the way to her? If no one raised an alarm, why not?

6. How do we know there was no classified material in those e-mails? What about “sensitive” material, and if they did include “sensitive” material, did her e-mail system meet State Department security requirements for the exchange of such information?

Here’s what we know about what was in the e-mails Clinton sent, via the New York Times:

“While the State Department has said there does not appear to be any classified material in Mrs. Clinton’s e-mails, officials said on Thursday that they needed to go through the trove again to determine whether it contained any ‘sensitive’ information.

“Sensitive information is different from classified information. It can be personal data, like Social Security numbers, or information on matters that other countries consider classified or important to their national security.”

So there “does not appear” to be any classified information contained therein, but it remains to be seen whether there was “sensitive” information. That sounds as if the State Department is giving itself lots of wiggle room.

It may turn out that no classified or even “sensitive” information was transmitted, but it’s quite clear that we — and the State Department — don’t know that yet. And since we don’t know that, we also don’t know whether there was ever a conversation between Clinton and State Department officials about how and whether she could send this sort of information via a private e-mail server.