Notes from the FBI's year-long investigation of Hillary Clinton's private email network offer fresh insight into the steps the former secretary of state and her team took to conceal their records from the public.

The 58 pages released Friday call into question many of Clinton's public statements about her server and prompted renewed criticism of the FBI's decision to close the investigation without recommending criminal charges for anyone involved.

While Clinton's campaign downplayed the presence of any new information in the FBI notes, the following 21 details were unknown before the report was made public.

We still might not have all the emails….

FBI agents indicated they were never able to determine whether they had all of Clinton's emails because none of her staff could remember where the original universe of records was located.

A witness whose name was redacted gave the FBI three different answers over the course of several interviews about where he collected the emails before turning select ones over to the government.

After his "inconsistent statements" failed to shed light on the location of the total email universe, agents used "forensic analysis" to search for the stash.

They never found it, nor did they determine the "composition" of the group of emails Clinton withheld.

...because they got lost in the mail

Clinton's unedited trove of emails existed in only one place: a laptop from the Clinton Foundation that was provided by Justin Cooper, one of the technology aides who oversaw the server system.

In spring 2013, Cooper instructed Clinton's assistant to archive all of Clinton's emails on the foundation's laptop and give it to Clinton. However, the assistant told the FBI she forgot to give the laptop to Clinton.

When reminded of that a year later, she deleted the laptop — but did not wipe it — at the instruction of the firm then responsible for managing Clinton's emails and told the FBI she mailed it to the Democratic nominee.

Clinton's staff said they never got the laptop and speculated that it must have gotten "lost" before it reached their office.

Why Clinton's IT aide needed immunity

Bryan Pagliano, the information technology aide who built the server Clinton used for most of her tenure, told the FBI he knew the system might be used to transmit classified materials at the time he set it up.

Pagliano's involvement in the case drew attention last year following the Justice Department's decision to grant him immunity in order to speak about the server.

The FBI did not elaborate on that deal in its investigative summary.

But it did reveal the fact that Pagliano was aware of the risks associated with Clinton's private email network and of numerous attempts over the years to breach that network.

An unidentified individual told Pagliano in 2009 that "he would not be surprised if classified information was being transmitted to Clinton's personal server."

Clinton's team lost all 13 mobile devices

Far from using just one mobile device to access all of her private emails for "convenience," Clinton and her aides may have logged onto the "clintonemail.com" network from 13 different devices.

In fact, she cycled through eight Blackberry phones during her tenure as secretary of state.

Clinton also may have used five different iPads to use her private email account. FBI agents said they received just three of those.

Her staff could not find any of the 13 cell phones when the investigation began, however.

Staff destroyed phones with a hammer

Aides told the FBI they could not remember what happened to most of Clinton's Blackberries, but in two cases, they said IT staffer Justin Cooper broke the phones when Clinton had finished using them.

"Cooper said he did recall two instances where he destroyed Clinton's old mobile devices by breaking them in half or hitting them with a hammer," the notes said.

Clinton claimed she got no classification training

When pressed by investigators about whether she realized the information in hundreds of her emails was classified, Clinton said she could not name a single example of how a document becomes classified.

She told FBI agents she could not remember ever receiving training on how to handle classified material, despite the fact that she signed her name to a form agreeing to the proper treatment of sensitive records.

The Democratic nominee mistook classified markings for alphabet letters

Clinton's longtime assertion that nothing in her inbox was marked classified fell apart in July when FBI Director James Comey first revealed that three emails bearing "confidential" markings had passed through her server.

In an interview with the FBI, Clinton said she thought the "C" in those three emails had been a way to alphabetize paragraphs and denied ever recognizing it as a classified marking.

Bill Clinton's office got classified emails

Agents discovered hundreds of emails were sent to an unidentified individual on the "presidentclinton.com" network.

That was the network originally set up on the server system in the basement of the Clintons' Chappaqua, N.Y., home when Hillary Clinton decided to shift her communications there at the outset of her State Department tenure.

According to the report, Huma Abedin, then Hillary Clinton's deputy chief of staff, forwarded classified emails to Bill Clinton's staff in order to print them.

Staff sent classified emails while overseas

Although Hillary Clinton and her aides were informed of the cyberthreats their inboxes faced when traveling abroad, they still sent classified information over their private network during overseas travel.

"Clinton and her immediate staff were notified of foreign travel risks and were warned that digital threats began immediately upon landing in a foreign country," the FBI report noted.

The full number of classified emails transmitted during foreign trips was redacted.

Hillary Clinton emailed Obama while overseas

Despite the risks about cybervulnerabilities in other countries, Hillary Clinton emailed President Obama while traveling abroad.

She stated she had asked for a secure Blackberry upon arriving at the State Department after learning that Obama used one in the White House.

Powell warned about private email use

Hillary Clinton has repeatedly attempted to justify her private email use by noting that Colin Powell, a fellow former secretary of state, used one as well.

She even suggested Powell had advised her to do so in the early months of her tenure.

But the FBI indicated Powell had in fact warned Hillary Clinton about the perils of using private email accounts, urging her to "be very careful" and to share few details about whatever network she used with the public should her personal email use become common knowledge.

A concussion blurred Hillary Clinton's memory

FBI agents asked the former secretary of state if she was advised on the proper method of turning over federal records to the government toward the end of her time at the State Department.

Hillary Clinton said she had suffered a concussion and then a blood clot toward the end of 2012 and therefore couldn't remember all the briefings she received during that period.

Aides said they didn't know the server existed

Even though Hillary Clinton's closest aides — Abedin, Cheryl Mills and Jake Sullivan — made up 68 percent of the former secretary of state's email traffic, they told FBI agents they did not know the private server existed.

Instead, the aides said they only learned of its existence when media reports about the server began to surface last year.

Emails were scrubbed after the scandal began

Hillary Clinton's private email use first became public knowledge in March 2015 following a New York Times report on the arrangement.

Shortly afterward, employees at Platte River Networks, a firm tapped to manage the network, applied a digital deletion tool called BleachBit to the server to erase old emails.

The Platte River Networks staff did so in violation of a preservation order from the House Select Committee on Benghazi, which was then pursuing Hillary Clinton's emails about Benghazi.

One unnamed employee told the FBI that he was aware of the order to save any potentially relevant emails when he made the deletions in March 2015, but chose to make them anyway.

Hillary Clinton withheld almost 17,500 emails

Beyond the trove of records Hillary Clinton's staff hand-picked for the State Department, the Democratic nominee withheld 17,448 emails.

The FBI did not specify how many of those records were personal in nature. However, agents did say that at least some of those emails were work-related.

Hillary Clinton has repeatedly insisted that she handed over everything that could have possibly been related to her government work when she submitted roughly 30,000 emails in late 2014.

Eighty-one email chains were classified when written

Contrary to her claim that nothing on her server was classified at the time it was put there, Hillary Clinton transmitted 81 classified email chains on her network.

Her staff withheld 12 of those classified chains from the State Department and the FBI. The others were included in the original batch of 30,000 emails.

Eight of the email chains were classified at the "top secret" level when they were written.

In total, 2,093 emails from the "clintonemail.com" network have been either retroactively classified or were considered classified from the start.

Hillary Clinton personally discussed top secret intel

Hillary Clinton spent most of her interview with the FBI blaming the presence of classified materials in her inbox on the foreign service officers and other government staffers who sent her the emails, claiming she simply relied on the judgement of other officials.

But the FBI discovered she had personally emailed top secret-level intelligence in four separate chains with other State Department officials.

In three additional chains, she discussed "secret"-level information, and emailed confidential information in four more chains.

At least one witness knew what was happening

One witness, whose name was redacted, acknowledged the fact that classified information was circulating on the unsecured network when he spoke to the FBI.

That witness admitted that information discussed over the email system "was technically probably classified" but told the FBI that "you can't do business that way," if they were to confine conversations to classified channels.

Aides cited the need to coordinate quickly on sensitive matters when stories were developing in the media, especially when senior-level officials like Hillary Clinton could not get to a SCIF — an area designed for the viewing of classified intelligence — in time to handle the issue.

A separate witness told the FBI he had read news articles suggesting the information in Clinton's emails had been over-classified but stated upon reading the emails during his interview that he "now understood why people were concerned about this matter."

Hillary Clinton withheld emails to Sidney Blumenthal

During her interview with the FBI, Hillary Clinton described the dozens of intelligence memos provided to her by Sidney Blumenthal, an informal adviser, as "journalistic" missives from a friend.

The FBI said it identified 179 such memos that Blumenthal had written to Hillary Clinton. That figure included two memos that Clinton did not provide to the State Department.

Agents recovered those two emails off "Blackberry backups" turned over by Cooper.

The server was hacked

FBI DIrector James Comey said in July that his agents found no evidence that Hillary Clinton's personal inbox had been hacked, although he added that the FBI would not expect to find evidence in the event that a breach did occur.

But at least one attack on the server appeared to succeed during Hillary Clinton's tenure, the FBI report noted.

Agents described "a successful compromise of an e-mail account on the server" on Jan. 13.

What's more, the FBI said the "clintonemail.com" domain saw a spike in cyberattacks following the New York Times story that revealed the existence of the server system.

Hillary Clinton's SCIF was not secure

The areas inside Hillary Clinton's homes in Washington, D.C., and Chappaqua that were designed for the secure viewing of classified material, known as SCIFS, were not used properly by the former secretary of state and her staff.

For example, the FBI said Hillary Clinton sometimes left the door of her Washington SCIF open so Abedin could come and go as she pleased. Investigators said her Chappaqua SCIF was "not always secure" either, as three different aides had "routine access" to the area.

The FBI also discovered that Hillary Clinton frequently brought her personal BlackBerry into the SCIF at her State Department office in clear violation of protocol.