When to Use?
Email headers provide key information regarding the origin and delivery of an email message. Often times this information is useful in determining whether or not a message is considered phishing or spam. Below are instructions describing the process of viewing message headers.
Procedure
For Outlook on Windows or online click here (external link)
For Outlook on the Mac:
In your inbox (or other folder), right-click or control-click the message, and then select View Source.
For Gmail please click here (external link)