Left click on the unsolicited email message so that it becomes highlighted.
Click on the "View" menu located at the top of the screen. Select the "All" option under "Headers".
The headers of the message should now be displayed on the lower part of your Messenger screen.
Scroll over the whole message with the left mouse button and all the text should become highlighted.
Right click on the highlighted text and a menu will appear on the screen. Left click on copy.
Paste the Text into the form.