Message Header

Message headers generally contain the identities of the author and recipients, the subject of the message, and the date the message was sent.

A term used to collectively describe all the header fields in an e-mail message. Header fields are part of the message content. Some header fields are required, while others are optional. Some header fields are created by user input, such as To:, Cc:, and Subject:. Other header fields are added by messaging servers that are involved in the routing of the message, such as Message-ID: and Received:. Still other header fields may be added by messaging applications, such as anti-spam and antivirus applications. The X.400 messaging standard equivalent to the message header is called the "P2 header." Defined in RFC 2822, the message header is often referred to as the "P2 header." [Exchange 2007]