The return (backward-pointing) address in the envelope is changed so that all error messages generated by the final deliveries will be returned to a list administrator, not to the message originator, who generally has no control over the contents of the list and will typically find error messages annoying.
- This the only difference between an SMTP alias and list; expanding recipients to RCPT commands is the same.
- Another great example to highlight the difference between SMTP envelope and mail data: the envelope's
MAIL FROM(see annotation) is different from to the mail data's rfc822From:.