Mail 3.0 Help
Showing header details
Each message you receive has a detailed “header” section that shows the route the message took on its way to you, as well as technical details about the message and sender. Your Internet service provider (ISP) or network administrator might ask you to send them a message with complete headers when you report problems or junk mail.
To show header details:
To see the routing information and complete headers for a message you’ve received, choose View > Message > Long Headers.
If there is a field in the long header list, such as X-Mailer, that you want to see for every message, you can customize the fields that Mail displays in all messages and add it. Choose Mail > Preferences, and then click Viewing. Choose Custom from the “Show header detail” pop-up menu. To add a header field, click the Add (+) button, type the field name (from the long header list), and click OK. To remove a field, select it in the list and click the Remove (-) button.
If you frequently want to view long headers, add the Long Headers icon to the toolbar.
You can create rules that perform actions based on the content of specific headers. For example, if the List-ID header contains “lists.example.com,” you could move the message to a specific folder.