Here's a summary of an SMTP rejection from Microsoft. I am quite sure that the message had a valid arxiv.org DKIM signature and was sent from an address in the SPF record. Anything I can do about it?
We've been sending this person mail for years at an outlook.com.au address and nearly all of them have worked, including several today. 550,5.7.515,Access denied, sending domain ARXIV.ORG doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. To learn how to fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Pass , Dkim= Fail , DMARC= Pass [SY8P300MB0731.AUSP300.PROD.OUTLOOK.COM 2026-05-08T18:21:38.150Z 08DEAD0640C37A36] [MW4PR04CA0059.namprd04.prod.outlook.com 2026-05-08T18:21:38.232Z 08DEACE91EBF534A] [MW1PEPF0001615B.namprd21.prod.outlook.com 2026-05-08T18:21:38.253Z 08DEACF5EA686851] R's, John _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
