In early March, an investigation by the New York Times' Michael S. Schmidt found that Hillary Clinton exclusively used a personal email account during her time as Secretary of State. She didn't even set up an official address. She wasn't using Gmail, either; she was "homebrewing" her emails with a server that "traced back to an Internet service registered to her family's home in Chappaqua, New York," according to the AP.

As a result, records of her work-related email correspondence weren't appropriately kept while she was there, instead only being turned over last year. We have no way of verifying that they've been properly turned over now, except for Clinton's word. President Obama said he learned about her email practices at "the same time everybody else learned it, through news reports."

A week after the initial revelation, Clinton said in a press conference that she used only the personal account "for convenience," because she "thought it would be easier to carry one device." She argued that she has fully complied with all laws and regulations. And, after a review, the State Department will publicly post the work-related emails she turned over.

But the controversy is raising uncomfortable questions for Clinton about transparency. In forgoing an official email address and setting up a system that allowed her to control the messages, she went further than other political figures in managing who can access her correspondence.

1) Why is Clinton's email use controversial?

RT @HuffPostPol: "Thanks for the many LOLZ" --Hillary "Hillz" Clinton to the Texts from Hillary guys http://t.co/7HSsf8E3 — Texts from Hillary (@textfromhillary) April 10, 2012

Exclusively using a personal account is a highly unusual practice for modern officials — and it meant many of Clinton's emails wouldn't become part of the State Department's records, or subject to Freedom of Information Act disclosure requests. "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 email accounts when they're conducting official government business," White House Press Secretary Josh Earnest said Tuesday.

Clinton got to pick and choose which of her emails to give the government

The New York Times' Schmidt also quotes several watchdogs and record-keeping experts harshly criticizing Clinton for her heavy reliance on private email.

The specific legal issue at play here, however, doesn't appear to be Clinton's use of her personal email — but rather the failure of Clinton and her aides to properly keep records of her work-related communications from that email account on State Department servers. Clinton said on March 10 that she "fully complied with every rule that I was governed by."

In 2014 (well after Clinton stepped down), in response to a query from the State Department (initiated by a House committee investigation into Benghazi), she turned over 55,000 pages of emails from her personal account that the department didn't previously have.

Clinton's team says she gave them all the ones relating to State Department business, but we basically have to take her word for that — she got to pick and choose which to give the government. And that makes some people wonder what Clinton might have left out.

2) So what was she using, Gmail or Yahoo?

Neither — instead, Clinton's personal email account instead appears to have been hosted at a domain called, appropriately, "Clintonemail.com." The AP's Jack Gillum and Ted Bridis reported that she used a "homebrew" system for maintaining the servers, and that her address was hdr22@clintonemail.com.

This domain, revealed in a 2013 Gawker post, was registered on January 13, 2009 — the day Clinton's Senate confirmation hearings began, writes Philip Bump of the Washington Post.

3) Is Clinton the only top-level official to avoid using a government email?

There was no requirement that Clinton set up a government email. Indeed, several recent Cabinet officials — including former Secretary of Defense Chuck Hagel and former Homeland Security Secretary Janet Napolitano — have opted not do so. In fact, the State Department says its current secretary, John Kerry, is the first ever "to use a standard government email address ending in 'state.gov'," according to the Washington Post's Anne Gearan. So it's certainly not odd for Clinton not to have an official email.

Some of these officials, however, just chose not to use emails for work at all, and rather to communicate through other means. For instance, Condoleezza Rice, who was secretary before Clinton, "generally did not use email during her tenure but when she did it was through the State Department system," a Rice aide told Steve Holland of Reuters.

Clinton, by contrast, emailed frequently, but always from her personal account. The closest comparison to what she did appears to be Colin Powell, who served as secretary of state between 2001 and 2005. Powell then "used personal email to communicate with American officials and ambassadors and foreign leaders," Schmidt writes.

But during Powell's tenure, rules about retaining records of personal emails were somewhat more ambiguous. In 2009, though — the year Clinton took office — the National Archives and Records Administration said that "agencies that allow employees to send and receive official electronic mail messages using a system not operated by the agency must ensure that Federal records sent or received on such systems are preserved in the appropriate agency recordkeeping system," Dylan Byers reports. Clinton argues that the use of personal emails for work was permitted, so long as records were kept.

4) So which emails from Clinton does the government have?

Emails from Clinton to US officials using their own government accounts should already have been in the system. In a statement, Clinton spokesperson Nick Merrill said that when Clinton emailed State employees, she used their State Department email addresses — so the government should have records of all those emails already, from the recipients' end. Emails by Clinton to White House officials or members of other departments are also likely to have been preserved by those agencies. That is, unless those aides also used personal accounts to correspond with Clinton.

On March 10, the State Department announced that, after a review that could take months, it would post the text of many of Clinton's emails on a public website. But when it comes to emails sent to people outside the government, the US apparently only has what Clinton and her aides chose to turn over in December 2014.

Clinton said on March 10 that there were 60,000 emails in total she had sent or received while Secretary. According to a review conducted by her team, half of these, she said, were work-related and given to the State Department. The rest were personal and have since been deleted.

However, the people with the strongest incentives to keep unflattering things secret — Clinton and her aides — got to decide what to withhold.

5) Was Jeb Bush much more transparent about his emails?

Transparency matters. Unclassified @HillaryClinton emails should be released. You can see mine, here. http://t.co/wZbtwd8O2j — Jeb Bush (@JebBush) March 3, 2015

When the news broke, likely GOP presidential candidate Jeb Bush immediately took a shot at Clinton on Twitter. Schmidt's Times story also mentions Jeb Bush as "stressing a different approach," and says he "released a trove of emails" from his tenure as governor of Florida.

But Bush also used a personal email account for work during that time — Jeb@Jeb.org — and decided which of those emails to turn over to the state. Mary Ellen Klas of the Tampa Bay Times writes:

"The former governor conducted all his communication on his private Jeb@jeb.org account and turned over the hand-selected batch to the state archives when he left office. Absent from the stash are emails the governor deemed not relevant to the public record: those relating to politics, fundraising and personal matters while he was governor."

Furthermore, Bush did post those emails publicly — after Florida law guaranteed they would become public anyway, and after they had already been posted on other sites. (Bush still gets points for making a good-looking website to browse through the emails, though it's lacking a search function.) A spokesperson confirmed Wednesday that Bush also owns the server where his emails are hosted, according to MSNBC's Kasie Hunt.

There are differences between Bush and Clinton's situations. Foreign governments would likely be much more interested in the emails of the US Secretary of State than the governor or Florida. Also, email was much newer when Bush took office in 1999, and different laws and regulations about email use apply to Florida and the federal government.

It does appear that Clinton didn't hand over any of her emails until the State Department asked for them nearly two years after she had stepped down. Then again, Bush stepped down as governor in 2007, and didn't finish handing over his emails to the state of Florida until 2014, according to Michael Bender of Bloomberg Politics.

6) We don't know what is missing from the record

One of the most pressing questions here has an unknowable answer. We do not know if Clinton sent and withheld emails to foreign leaders or businessmen. We can only go on what her staff assures us.

In an email, Clinton spokesperson Nick Merrill says that classified information was "never" sent from the Clintonemail.com domain. As to whether Clinton emailed foreign or leaders and foreign officials, Merrill writes, "Except on only the rarest of occasions, for instance with a UK official, that was simply not her practice." And, he says, emails such as those would have been turned over to State.

7) This sounds familiar. Which other politicians have tried to avoid email disclosure?

Recent history has been full of colorful examples of politicians and public officials attempting to shield their personal emails from the public. Here are just a few.

The George W. Bush administration : As Max Fisher writes, George W. Bush's second presidential term was marked by controversies over email records.

: As Max Fisher writes, George W. Bush's second presidential term was marked by controversies over email records. John Kitzhaber : The scandal-plagued Democratic governor of Oregon "requested state officials destroy thousands of records in the governor's personal email accounts" — a request those officials refused to carry out, reported Nigel Jaquiss of the Willamette Week.

: The scandal-plagued Democratic governor of Oregon "requested state officials destroy thousands of records in the governor's personal email accounts" — a request those officials refused to carry out, reported Nigel Jaquiss of the Willamette Week. Mitt Romney : In 2007, the outgoing governor of Massachusetts "had emails and other electronic communications... wiped from state servers," according to Mark Hosenball of Reuters.

: In 2007, the outgoing governor of Massachusetts "had emails and other electronic communications... wiped from state servers," according to Mark Hosenball of Reuters. Scott Walker: While Milwaukee County Executive, Walker and his aides used what the Milwaukee Journal Sentinel called "a secret email system" to "avoid public scrutiny" — and to allow his government staff to communicate about his campaign during working hours. Indeed, they even set up a new router in the office to help them do so.

Additionally, there are the many missing emails from former IRS official Lois Lerner , purportedly lost in a hard-drive crash, which many members of Congress are still quite curious about. An inspector general looking into the matter recently said there was "potential criminal activity" around the emails.

This post was updated to include new developments.