The FBI investigation found that 110 messages contained information that was classified at the time it was sent. Sixty-five of those emails were found to contain information classified as "Secret;" more than 20 contained "Top-Secret" information.[111][112] Three emails, out of 30,000, were found to be marked as classified, although they lacked classified headers and were only marked with a small "c" in parentheses, described as "portion markings" by Comey....
According to the State Department, there were 2,093 email chains on the server that were retroactively marked as classified by the State Department as "Confidential," 65 as "Secret," and 22 as "Top Secret."...
A July 17, 2015, follow-up memo, sent jointly by Linick and the Intelligence Community (IC) inspector general, I. Charles McCullough III, to Under Secretary of State for Management Patrick F. Kennedy, stated that they had confirmed that several of the emails contained classified information that was not marked as classified, at least one of which was publicly released.....
On July 24, 2015, Linick and McCullough said they had discovered classified information on Clinton's email account,[125] but did not say whether Clinton sent or received the emails.[125] Investigators from their office, searching a randomly chosen sample of 40 emails, found four that contained classified information that originated from U.S. intelligence agencies, including the Central Intelligence Agency (CIA) and the National Security Agency (NSA).[125] Their statement said that the information they found was classified when sent, remained so as of their inspection, and "never should have been transmitted via an unclassified personal system.....
On August 10, 2015, the IC inspector general said that two of the 40 emails in the sample were "Top Secret/Sensitive Compartmented Information" and subsequently given classified labels of "TK" (for "Talent Keyhole," indicating material obtained by aerial or space-based imagery sources and NOFORN).....
On January 29, 2016, the State Department announced that 22 documents from Clinton's email server would not be released because they contained highly classified information that was too sensitive for public consumption....