State Department official Claire Coleman emails Clinton her daily schedule early in the morning. It mentions a photo opportunity with a person. The person’s name will later be redacted, but the context makes it clear it is the secret CIA official who gives her a daily intelligence briefing.
The New York Times will later report, “That email was originally released as ‘confidential’ but upgraded to ‘secret,’ probably reflecting that the person holds an undercover position now.” (US Department of State, 1/29/2016) (The New York Times, 5/10/2016)
Clinton sends a reply which is also classified at the “secret” level. (US Department of State, 2/29/2016)