To view the full headers for an email in Thunderbird:
- Select the email message and then press the keys "Ctrl" and "U" at the same time.
You can also click on the Thunderbird menu in the top right, select "View" and then select "Message Source"
- The message headers will appear in a new window
To copy the full headers:
- In the message headers window that appears, select all by pressing "Ctrl" and "A" at the same time.
Or you can click on the edit menu in the tool bar at the top of the window and then click on the "select all" option.
- Once the headers are selected, press "Ctrl" + "C" to copy the content or click on the edit menu and select copy.