Yes! You can look at the original source of the email.
Open the email in Gmail, click the three-dot menu in the top right, click "show original". A new tab will open with the raw email including all the headers.
Wow, thanks. Live and learn. Does the way some tools check whether the email was read by the recipient or not have something to do with this structure, too?
Actually no it's not, most read-trackers use invisible images in the email body. When you open the email the images all load from their remote server, and thus they know you opened the email, and when.
You can work against this by disabling images, or you can add a tracker list I made to your adblocker!
