Email Header Definition and Details

You may need to view an email's headers during troubleshooting

Although you rarely see the complete email header of an email, it contains routing information that is indispensable for delivering the mail to the proper recipient, wherever that person is.

The Role Email Headers Play

Every email consists of two parts: the header information and the body of the message. Email header lines contain behind-the-scenes information that makes up the first part of an email message. They control the transmission of the message as well as metadata such as the subject, origin and destination email addresses, the path an email takes, the servers it passes along the way and the time it did so, and sometimes its priority.

Header lines are normally not displayed by email programs. Only certain information—the subject line, sender and sent date—is displayed and formatted for easy use. Optionally, the Cc and Bcc fields can be displayed. They are also included in the headers.

How to See an Email Header

Email headers are not particularly friendly to the untrained eye, and the header is often longer than the email itself. Most email clients provide a way for you to display the email headers if you are curious. For example, using the Mail app on a Mac, choose View > Message > All Headers. In Yahoo mail in a browser, open an email and select View Raw Message from the More icon at the bottom of the email. In AOL, open an email and choose More > View Message Source to see the headers.

Why View an Email Header

Most people never need to view the complete email header lines of an email. However, you may be asked by a technician during troubleshooting an email problem to send the complete headers for evaluation, or you may be able to use them to identify a spam sender or verify the email is a spoof or phishing attempt.