When you receive an email, you receive more than just the message. The email comes with headers that carry important information that can tell where the email was sent from and possibly who sent it. For that, you would need to find the IP address of the sender. The tutorial below can help you find the IP address of the sender.

Log into your Gmail account with your username and password.

Open the mail.

To display the headers,
Click on More options corresponding to that thread. You should get a bunch of links. Click on Show original

You should get headers like this:
Gmail headers : Mastitrain

Look for Received: from followed by a few hostnames and an IP address between square brackets. In this case, it is

That is be the IP address of the sender!!