Question: What was the official communication including over 100 emails which contained classified information which was investigated by the 7th director of the Federal Bureau of Investigation?

Context articles: Presidential Policy Directive 19
Sigurdur Thordarson
Hillary Clinton email controversy
Kenneth Eichner
Bush White House email controversy
Standard Form 312
Dismissal of James Comey
Classified information
National Security Higher Education Advisory Board
Stewart Nozette

The United States Presidential Policy Directive 19, signed by President Barack Obama, is designed to ensure that employees who serve in the Intelligence Community or have access to classified information can effectively report waste, fraud, and abuse, while protecting classified information.
 It is the executive order establishing standards for all Federal agencies with employees covered by the Directive, including those under Defense Intelligence Community Whistleblower Protection and the U.S. Department of Defense Whistleblower Program.
 It also prohibits retaliation against these employees for their reports.
 PPD-19 accordingly establishes a system of Intelligence community whistleblowing and source protection under the Office, Director of National Intelligence and supervised by the Inspector General of the Intelligence Community (IC IG).
Sigurdur Thordarson (Sigurður Ingi Þórðarson) was born in 1992 in Reykjavík.
 He is known for his involvement with the whistleblowing organization WikiLeaks, as well as his interactions with the Federal Bureau of Investigation (FBI).
 In 2010 he was arrested for stealing and leaking classified information about the bank structure in Iceland.
 He obtained the information from a lawyer that aided wealthy people in tax evasion, whose name was Gunnar Gunnarsson.
 Gunnar worked for an investment firm called Milestone ehf.
 Gunnar obtained Sigurdur's services to set up computer systems and delete data.
 After Sigurdur was arrested he was introduced to Julian Assange, the editor and founder of WikiLeaks.
 Sigurdur started his time there in early 2010, and participated in preparing many of WikiLeaks's biggest leaks.
 After a year in WikiLeaks service Sigurdur was suspected of embezzling funds from the WikiLeaks online store.
 WikiLeaks filed criminal charges against Sigurdur with the Metropolitan Police of Iceland, who investigated the case and later dropped it due to lack of evidence.
 Sigurdur later plead guilty to the embezzlement along with other economic crimes, in 2013.
 Sigurdur was ordered to pay the victims 15 million ISK (roughly $115,000)
In March 2015, it became publicly known that Hillary Clinton, during her tenure as United States Secretary of State, had used her family's private email server for official communications, rather than official State Department email accounts maintained on federal secure servers.
 Those official communications included over 100 emails which contained classified information at the time they were sent, as well as nearly 2,100 emails which were not marked classified but would retroactively be ranked as classified by the State Department.
Kenneth Frank Eichner (born July 29, 1954) is an American author, trial lawyer, and film producer based in Denver, Colorado.
 Before rising to prominence as a defense attorney Eichner was a prosecutor in Prince George's County, Maryland.
 Eichner is legal counsel for presidential candidate Hillary Clinton’s server company, Platte River Networks, in the Federal Bureau of Investigation and Department of Justice National Security Division’s inquiry into the handling of classified information.
During the 2007 Congressional investigation of the dismissal of eight U.S. attorneys, it was discovered that administration officials had been using a private Internet domain, called gwb43.com, owned by and hosted on an email server run by the Republican National Committee, for various official communications.
 The domain name is an abbreviation for "George W. Bush, 43rd" President of the United States.
 The use of this email domain became public when it was discovered that J. Scott Jennings, the White House's deputy director of political affairs, was using a gwb43.com email address to discuss the firing of the U.S. attorney for Arkansas.
 Communications by federal employees were also found on georgewbush.com (registered to "Bush-Cheney '04, Inc.") and rnchq.org (registered to "Republican National Committee").
 Congressional requests for administration documents while investigating the dismissals of the U.S. attorneys required the Bush administration to reveal that not all internal White House emails were available.
 Conducting governmental business in this manner is a possible violation of the Presidential Records Act of 1978.
 Over 5 million emails may have been lost.
 Greg Palast claims to have come up with 500 of the Karl Rove emails, leading to damaging allegations.
 In 2009, it was announced that as many as 22 million emails may have been lost.
Standard Form 312 (SF 312) is a non-disclosure agreement required under Executive Order 13292 to be signed by employees of the U.S. Federal Government or one of its contractors when they are granted a security clearance for access to classified information.
 The form is issued by the Information Security Oversight Office of the National Archives and Records Administration and its title is "Classified Information Nondisclosure Agreement."
 SF 312 prohibits confirming or repeating classified information to unauthorized individuals, even if that information is already leaked.
 The SF 312 replaces the earlier forms SF 189 or the SF 189-A.
 Enforcement of SF-312 is limited to civil actions to enjoin disclosure or seek monetary damages and administrative sanctions, "including reprimand, suspension, demotion or removal, in addition to the likely loss of the security clearance."
James Comey, the 7th director of the Federal Bureau of Investigation (FBI), was dismissed by U.S. President Donald Trump on May 9, 2017.
 Comey had been under public and political pressure as a result of both the FBI's role in the Hillary Clinton email controversy and the FBI's investigation of Russian interference in the 2016 U.S. elections, which also involves a possible collusion with the 2016 Donald Trump campaign.
Classified information is material that a government body claims is sensitive information that requires protection of confidentiality, integrity, or availability.
 Access is restricted by law or regulation to particular groups of people, and mishandling can incur criminal penalties and loss of respect.
 A formal security clearance is often required to handle classified documents or access classified data.
 The clearance process usually requires a satisfactory background investigation.
 Documents and other information assets are typically marked with one of several (hierarchical) levels of sensitivity—e.g. restricted, confidential, secret and top secret.
 The choice of level is often based on an impact assessment; governments often have their own set of rules which include the levels, rules on determining the level for an information asset, and rules on how to protect information classified at each level.
 This often includes security clearances for personnel handling the information.
 Although "classified information" refers to the formal categorization and marking of material by level of sensitivity, it has also developed a sense synonymous with "censored" in US English.
 A distinction is often made between formal security classification and privacy markings such as "commercial in confidence".
 Classifications can be used with additional keywords that give more detailed instructions on how data should be used or protected.
The National Security Higher Education Advisory Board (NSHEAB) was created by American Federal Bureau of Investigation (FBI) Director Robert S. Mueller III on December 15, 2005.
 Operated by the FBI and paneled by approximately 20 American university presidents and chancellors, the expressed purpose of the board is "to foster outreach and to promote understanding between higher education and the Federal Bureau of Investigation."
 The board also facilitates communication between universities and federal authorities on "national priorities pertaining to terrorism, counterintelligence, and homeland security."
 NSHEAB meets approximately three times yearly and includes representatives from the Central Intelligence Agency and other security agencies.
Stewart David Nozette (born May 20, 1957) is an American planetary scientist, technologist, and consultant who worked for the United States Department of Energy, the United States Department of Defense, DARPA, the United States Naval Research Laboratory, and NASA.
 He is also a convicted felon for attempted espionage and fraud against the United States.
 The FBI arrested him October 19, 2009, charging him with attempted espionage after a sting operation which Nozette's lawyer claims amounted to entrapment.
 At trial, Nozette admitted attempting to sell U.S. classified information to someone he believed was an Israeli Mossad operative, but was in reality an undercover Federal Bureau of Investigation employee.
 He pleaded guilty to one charge of attempted espionage and was sentenced, under the terms of a plea bargain, to thirteen years in prison and is now serving time at the Federal Correctional Institution, Terre Haute.
 The FBI found no evidence that any classified materials were actually released to anyone outside the US Government.