Email headers are essential for diagnosing any email related issue. An email header contains information for individual emails which tracks the path an email takes through each email server, or hop, it takes. This information can include items such as IP addresses, time stamps, sender and recipient details, and authentication details. Reviewing this information is useful in troubleshooting email delivery issues.
In order to grab the message header for an individual email, please follow the steps below.
Getting Email Headers
Step 1: Open the email you want to retrieve the headers from and click the ellipsis (three dots) in the right-corner.
Step 2: Once you open the option menu for the ellipsis, select "Show Original." It should direct you to a new window with the message details.
Step 3: In the new window, click the "Download Original" option, which will download an eml file that includes the full message header information.
Note: You can also copy and paste the information in the same window to a .txt file to attach to any case.
How to read email full headers 
- Once you have the eml file downloaded, navigate to https://toolbox.googleapps.com/apps/messageheader/ where you will be able to upload your message header, and analyze its content.
- Open the EML file or TXT file, and copy the entirety of the contents. You will need to paste this in the field.
- Once you have pasted the entire contents, go ahead and select "Analyze the header above"
- You will now be able to review the header information through this Google provided tool.