title: X-Originating-IP
text: # X-Originating-IP
  
  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 of a client connecting to a mail service's HTTP frontend. When clients connect directly to a mail server, 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: [198.51.100.1]
  
  ## Origins
  
  In 1999 Hotmail 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.
  
  