SMTP Service Extension for Indicating the Responsible Submitter of an E-Mail Message

This memo defines an extension to the Simple Mail Transfer Protocol (SMTP) service that allows an SMTP client to specify the responsible submitter of an e-mail message. The responsible submitter is the e-mail address of the entity most recently responsible for introducing a message into the transport stream. This extension helps receiving e-mail servers efficiently determine whether the SMTP client is authorized to transmit mail on behalf of the responsible submitter's domain. This memo defines an Experimental Protocol for the Internet community.