What is an email header?


Email Header lines make up the first part of any email message. They contain information used to control the message and its transmission as well as metadata such as the Subject, origin and destination email addresses, the path an email takes, and maybe its priority.


This tutorial will show you how to retrieve the email headers from an email client e.g. Outlook.


Outlook 2010 / 2016


Double click on the email message so that it is opened in its own window.




On the Message tab, in the Options section there is a little button with an arrow in it. Click on it and you have the message options menu with the internet headers in the bottom section. 



This will bring up the Message Options window. The last component of this is the Internet Headers. 





Entourage


To begin, open the email message in a new window by double-clicking on it.

Choose View > Internet Headers.



Mac Mail


To begin, open the email message in a new window by double-clicking on it.


In the menu bar, click on View, then Message, then All Headers (or Raw Source on older versions of Mail).



Gmail


Open the message you’d like to view headers for.


Click the down arrow next to Reply, at the top-right of the message pane


Select Show original.