A State Department official named Matthew Eussen sends an email to over two dozen other US officials about the latest violent developments between Israeli and Palestinian forces in Gaza. Two of the names sent the email will later be redacted, and the redaction code indicates those people secretly work for the DIA (Defense Intelligence Agency), NRO (National Reconnaissance Office), or NGA (National Geospatial-Intelligence Agency).
The next day, another State Department official, Thomas Goldberger, replies with more details, and this email is sent to the same group of US officials, including the two later redacted names. This email includes two and a half lines of text that will also be later redacted for containing secret information relating to the DIA, NRO, or NGA.
These emails get forwarded to Clinton’s deputy chief of staff Huma Abedin, and Abedin then forwards them to Clinton. (US Department of State, 2/29/2016)