The headers of a message provide detailed information on the routing of a message and are an immense help in troubleshooting email-related issues. Because they contain more information than most would need or want, they are usually available but hidden.
Here is how to find email headers in some of the most popular email clients:
In the email -> Go to top-right corner, Click the "more" dropdown -> Select View Source
Highlight the message -> Go to View at the very top -> Message -> All Headers
Double-click the message so it opens in its own window >> Go to File->Properties >> Headers are displayed in properties box near the bottom
From the message, go to the upper right-hand side >> Click the 3 dots >> Select Show Original
From email message >> Top center next to "Spam", Click 3 dots >> Click View Raw Message
Click Message >> In message screen go to top right-hand side >> Click the dropdown >> Select View message source