A message header (also called email header) is
|“||the information at the beginning of an e-mail or bulletin board message. Message headers contain the identities of the author and the recipients, the subject of the message, and the date the message was sent.||”|
|“||[t]he part of a message that contains the protective marking, precedence, the criticality and the subject of the message. In addition, it includes the addressees to whom the message is to be sent.||”|
- Glossary of Communication Electronic Terms, at 2-100.