Incoming mail messages contain information about the routing of the message between its sender and you. By default, most mail programs don’t automatically display all of this information for you. You will see the basic header information (such as From, Subject, Date, and To) but the rest of the header information is normally hidden from view. However, sometimes you will need or want to display headers, especially if you are getting support from the IT Help Center about a specific issue.

Here is how to view header information:

Mozilla Thunderbird
When reading mail, choose View-Headers-All. Hide them again with View-Headers-Normal.

Outlook 2010
Double-click to open the message you want headers for. Then go to File and click on Properties (on the Info tab). You will then see the Internet headers at the bottom of the window.  If you need to email the full headers to the Help Center, you can select, copy, and paste the header text.

Outlook 2003
Right-click on the message and choose Options. You will see the Internet headers at the bottom of the window. If necessary, you can select, copy, and paste the header text to get it into a format that you can send.

OS X Mail
Go to the View menu and select Message and then Long Headers or even better, if the option is available, choose Raw Source. To copy this information into a new message, you may then choose Edit:Copy, open a new message, and choose Edit:Paste.

Eudora
Double-click the message to open it in a new window, and full headers will display.

Pine
When viewing a message, press the H key. This turns on display of full headers for all messages. When you want to turn the full header display off, press the H key again.

Yahoo
Open the mail message, then scroll down to the bottom of the message, and click on Full Headers, which is right justified along the line that has “Previous,” “Next,” etc.

The message will not forward with full headers, but you can copy and paste the displayed headers into another mail message.