What is a classified email header, do they even exist?

Question

Topical question related to current news:

"Classified material has a header which says ‘top-secret, secret, confidential.’ Nothing, and I will repeat this and this is verified in the report by the Department of Justice, none of the emails sent or received by me had such a header."

— Hillary Clinton on Wednesday, September 7th, 2016 in the NBC Commander-In-Chief Forum

I was curious after reading this and wondered is there such a thing as a classified or top-secret email header? The quote seems to suggest it is just put in the subject line. Googling this is impossible because of all the news articles that come up. Is there such a thing as something like "X-Header: classified information"?

Answer 1

I was curious after reading this and wondered is there such a thing as a classified or top-secret email header?

The header the quote is talking about is an approved header (statement) that must appear in the email, before and after any classified material within the body of the email that is being sent, failure to do this is a security violation.

In addition each paragraph, within the body of the email, must also be individually marked with its classification. The header indicates the overal classification of the email. The highest classification of the content within the email, determines, the classification of the email itself.

What the header says exactly, will be different, for each type of classification.

The quote seems to suggest it is just put in the subject line.

If the body of the email contains classified material, the subjectline must also be properly marked, failure to do this is a security violation.

Is there such a thing as something like "X-Header: classified information"?

The header they are talking about is an approved statement that must come before and after any and all classified material. There is no such thing as a Classified X-Header in the specifications that cover emails.

Googling this is impossible because of all the news articles that come up.

Very few people, would post the actual contents of the header online, because the statement is pretty generic. The primary purpose is that it states the classificiation of the material, in the same way, all classified material is marked.