To get an email header from Gmail simply open the email within your web browser, click the drop down arrow (more) next to the reply button and choose "Show Original".
Once the new page opens (example not shown for security reasons), select Ctrl+A then Ctrl+C to copy all of the data within the window on a PC. On a Mac, select Cmd+A then Cmd+C to copy all data within the window.
Once all data is copied, head over to our Email Header Analyzer Tool and paste (Ctrl+v for PC or Cmd+v for Mac) that data into the tool window. Hit Analyze to get your results.