Email Headers

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• standard for email format is RFC 2822
• email headers include:
  • a record of the emails journey through networks
    • each server adds its own info to the message header
• email message header includes:
  • required fields
    • From field
    • Date
  • recommended:
    • message-ID
    • in-reply-to field
      • used to link related messages together

Email Header Fields

• RFC 3864 describes message header field names:
  • To
    • email address and name of primary recipient
  • Subject
    • brief summary of the topic of the message
  • Cc
    • carbon copy; a copy is sent to secondary recipients
  • Bcc
    • blind carbon copy; a copy is sent to addresses added to the SMTP delivery list
    • address remains invisible to other recipients
  • Content-Type
    • info about how the message is to be displayed
    • typically Multipurpose Internet Mail Extensions (MIME) type
  • Precedence
    • used to indicate that automated “vacation” or “out of office” responses should not be returned for this mail
    • e.g., prevents vacation notices from being sent to all other subscribers of a mailing list
    • common values: bulk, junk, list
  • Received
    • tracking information generated by mail servers that have previously handled a message
    • in reverse order (last handler first)
    • shows the trail of an email message from the sender to its recipient
      • origin is listed at the bottom
  • References
    • Message-ID of the message to which this is a reply
  • Reply-To
    • used to specify the recipient when you reply to the email
    • address that should be used to reply to the message
  • Sender
    • address of the actual sender acting on behalf of the author listed in the From Field