Sender ID

Internet Security. A deprecated email authentication standard that checked that a domain authorized a given email address to send on its behalf. RFC 4406 defines this standard.

This standard fell out of favor for two reasons:

• It relies on a Purported Responsible Address (PRA) in the email header. RFC 4407 defined this standard. The PRA conflicted with existing email forwarding and mailing list mechanism and caused deliverability issues.
• Microsoft owned the patents for key parts of the standard. That was incompatible with many open source licenses.

To authenticate email, organizations moved on to domain authentication.