This too caught me off guard. It is indeed Microsoft. It is only ever used for outbound messages. There are no gateways on it.
Thanks, Michael Irvine -----Original Message----- From: mailop <[email protected]> On Behalf Of Marco Moock via mailop Sent: Wednesday, December 10, 2025 10:35 To: [email protected] Subject: [mailop] strange MS Teams bounces CAUTION: This email originated from outside of the organization. Do not click any links or open attachments unless you recognize the sender and know the content is safe. Hello! Today I posted to a mailing list (not hosted at MS) and that post got delivered to the subscribers (myself included). I then got a strange "bounce" (return path is <[email protected]>) from MS teams. It is indeed form MS's servers. Received: from SN4PR0501CU005.outbound.protection.outlook.com (mail-southcentralusazlp170110003.outbound.protection.outlook.com [IPv6:2a01:111:f403:c10d:0:0:0:3]) by srv1.dorfdsl.de (8.18.1/8.18.1/Debian-6) with ESMTPS id 5BAGN68Q213851 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT) for <[email protected]>; Wed, 10 Dec 2025 17:23:07 +0100 ########### Delivery has failed to these recipients in Microsoft Teams: [email protected]<[email protected]> We couldn't deliver this message to Teams, because it was flagged by anti spam policies. Diagnostic info for admins: messageId: <4887a27fc84244efa8cb0fbd68aaa...@bn0pr10mb4982.namprd10.prod.outlook.com>, serverRequestId: 50438e9a-b6a6-45ac-94d2-f064cf9ff8d3, clientRequestId: - This email is generated through the use of Microsoft 365 and may contain content that is controlled by your Organization's IT Admin. ############## Does anyone know what that is? I know Teams as a chat and call application. Is there also a mail gateway? -- kind regards Marco Send unsolicited bulk mail to [email protected] _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
