Dear *, I am seeing a worsening problem with automated emails from M365 transiting through my mail relays linked in particular to calendar invitations and notifications about unread messages in Teams, i.e. all automated emails generated by the relevant M365 subsystem. I am quite confident that emails sent by “humans” via Outlook are fine.
The symptoms are easily explained: * the Message-Id is invalid * the outbound Exchange relay in outbound.protection.outlook.com presents a different hostname at SMTP HELO than the PTR records, e.g. mail-northeuropeazlp17010004.outbound.protection.outlook.com vs. DB3PR0202CU003.outbound.protection.outlook.com * the SPF records check (FORGED_SPF_HELO) fails because of the above * DMARC check fails because of the above The exact rules failing are: 1.2 INVALID_MSGID Message-Id is not valid, according to RFC 2822 1.0 FORGED_SPF_HELO No description available. 1.8 DMARC_REJECT DMARC reject policy Anyone else seeing this behaviour? Cheers, Arrigo _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
