Check the MX records. Did the domain/tenant recently move on or off of Office365?
Aloha, Michael. -- Michael J Wise Microsoft Corporation| Spam Analysis "Your Spam Specimen Has Been Processed." Open a ticket for Hotmail<http://go.microsoft.com/fwlink/?LinkID=614866> ? From: mailop <mailop-boun...@mailop.org> On Behalf Of Scott Q. via mailop Sent: Thursday, October 2, 2025 9:42 AM To: mailop@mailop.org Subject: [EXTERNAL] [mailop] MS365 mail loop One of our customers is getting this message when e-mailing a specific address hosted @ MS365: 52.101.41.26 failed after I sent the message. Remote host said: 554 5.4.14 Hop count exceeded - possible mail loop ATTR1 [SJ1PEPF00002313.namprd03.prod.outlook.com 2025-10-01T14:52:23.190Z 08DE008E05DFD276] but it works fine if we use a different address as source, aka a random Gmail. Anyone else saw this and know what it might be ? Thanks! Scott
_______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
