Years ago they would include the IP of the end user. Gmail and hotmail stopped including that more than a decade ago. But they both used to. I think Gmail stopped this practice years ahead of Hotmail.

I have a relative with mental health problems who lives on the street, and he sometimes writes me from public libraries -- kind of luckily for family members who are concerned about him, the webmail service he uses still includes that info in headers. So I usually know which public library he writes from.