Email headers contain information all the way back to the sender. This is how email was designed to work and cannot be changed, no matter what you may read on the Internet. The bigger question here is, exactly why is this important to you?
"In that, your success with tracing an email will vary depending on the email provider of the sender. If you're trying to trace an email sent from a Gmail account, you'll only find out the location of the last Google server that processed your email---not the IP address of the original sender." https://www.makeuseof.com/tag/how-to-trace-your-emails-back-to-the-source/
This article seems to teach how to track ip address of real sender in gmail, but the comments say it does not work, can any expert here verify if the article is true or is the gmail sender IP address just one of the server of gmail? https://www.webnots.com/how-to-track-ip-address-of-real-sender-in-gmail/