As previously reported, on May 17th, the outbound traffic from all IETF list mails stopped. After the issue was repaired, members of the IETF Community requested an explanation of the nature of the problem. This message provides a summary of the problem and the steps taken to correct it. The cause was an incorrect configuration of the dmarc-rewrite program that was made to activate the DMARC processing for domains with 'reject' as their policy. The incorrect configuration was provided by the Tools Team. Although testing was done on five mail lists before this was activated for all mail lists, the testing did not catch this problem. The incorrect configuration of the dmarc-rewrite program caused it to bounce all outbound deliveries back to Mailman, and then Mailman interpreted the returned messages as destination delivery bounces, discarding them. Since they were discarded, the Secretariat could not automatically resend these messages for the authors. The Secretariat temporarily disabled the dmarc-rewrite program so that outgoing messages were flowing again. Then, the Secretariat worked with the Tools Team to correct the configuration of the dmarc-rewrite program. In less than a day, the configuration was corrected and the DMARC processing was working properly for all mail lists. Alexa Morris IETF Executive Director
