External Web Articles for Mac and non-Outlook users
Be sure to select the Outlook Web Access option to view the internet headers | Microsoft Support link
Step-by-Step Guide for Windows Outlook 2016 & 2019
Open the desired message in a separate window.
Go to the File tab and select Info.
To find the source of the email, select the text Internet headers section. (CTRL+ A)
Copy the Internet Headers and past into a text file using NotePad
Save the file and it to the IT Department helpdesk.
Select Close when you're finished.