The X-Originating-IP (not to be confused with X-Forwarded-For) email header field is a de facto standard for identifying the originating

IP address An Internet Protocol address (IP address) is a numerical label such as that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface i ...

of a client connecting to a mail service's HTTP frontend. When clients connect directly to a

mail server Within the Internet email system, a message transfer agent (MTA), mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using the Simple Mail Transfer Protocol. In some contexts, the a ...

, its address is already known to the server, but web frontends act as a proxy which internally connect to the mail server. This header can therefore serve to identify the original sender address despite the frontend.

Format

The general format of the field is:

X-Originating-IP:  98.51.100.1/code>

  Origins 

In 1999 Hotmail 





Outlook.com, formerly Hotmail, is a free personal email service offered by Microsoft. It also provides a webmail interface accessible via web browser or mobile apps featuring mail, Calendaring software, calendaring, Address book, contacts, and ...
 included an ''X-Originating-IP'' email header field that shows the IP address of the sender. As of December 2012, Hotmail removed this header field, replacing it with X-EIP (meaning encoded IP) with the stated goal of protecting users' privacy.what does X-EIP mean in an email message source
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  See also 

* Internet privacy 
Internet privacy involves the right or mandate of personal privacy concerning the storage, re-purposing, provision to third parties, and display of information pertaining to oneself via the Internet. Internet privacy is a subset of  data privacy. P ...

*  List of proxy software
*  X-Forwarded-For

  References 



 Anonymity
 Email
 IP addresses