>As for any claim that DMARC 'extends' SMTP or DNS, it's difficult to >imagine the technical logic behind such an assertion. The argument that it extends SMTP is not totally ridiculous. Where did these SMTP rejections come from, if not DMARC? 2014-04-07 08:18:59.693287500 delivery 117461: failure: 2607:f8b0:4001:0c03:0000:0000:0000:001b_failed_after_I_sent_the_message./Remote_host_said:_550-5.7.1_Unauthenticated_email_from_yahoo.com_is_not_accepted_due_to_domain's/550-5.7.1_DMARC_policy._Please_contact_administrator_of_yahoo.com_domain_if/550-5.7.1_this_was_a_legitimate_mail._Please_visit/550-5.7.1__http://support.google.com/mail/answer/2451690_to_learn_about_DMARC/550_5.7.1_initiative._k7si18580912icu.45_-_gsmtp/ 2014-04-07 08:19:00.680001500 delivery 117452: failure: 2607:f8b0:4001:0c03:0000:0000:0000:001b_failed_after_I_sent_the_message./Remote_host_said:_550-5.7.1_Unauthenticated_email_from_yahoo.com_is_not_accepted_due_to_domain's/550-5.7.1_DMARC_policy._Please_contact_administrator_of_yahoo.com_domain_if/550-5.7.1_this_was_a_legitimate_mail._Please_visit/550-5.7.1__http://support.google.com/mail/answer/2451690_to_learn_about_DMARC/550_5.7.1_initiative._c1si22721698igj.35_-_gsmtp/ R's, John