Displaying The Header
An email message is made up of three components: a message envelope, a message header, and a message body. Sometimes one is interested in the originating IP address of a digital message and other pertinent header information, but Google does not display it by default. To view an email header in Gmail you have to open a particular message. On the right side at the top of the message, right beside the reply arrow button, select the drop down arrow key.
Select Show original. The message will open in a new window.
The Gmail header needs to be read bottom-up:
In the To: field - above Date: - you will find the recipient(s) (including your) email address(es). It may or may not include the name(s) of the recipient(s).
Above the To: field will see a From: field. This is the sender’s email address.
Above the From: field there will be one or more Received: from – fields. Inspect the last near the end of header. The four octets in square brackets are the IP address of the sender, loosely speaking the IP Address in Gmail.
Received: from zdmta.response.enterprise-alerts.com (zdmta.response.enterprise-alerts.com [220.127.116.11])
This message was sent from the host zdmta.response.enterprise-alerts.com with the IP address of 18.104.22.168.