iBiblio's SMTP server is rejecting outgoing emails (using "mail.protection.outlook.com")

Recently outgoing emails from our project (“confluence”) have been failing, apparently due to some service “mail.protection.outlook.com” that your SMTP server uses. Here’s an example:

Diagnostic information for administrators:

Generating server: its-msxhybrid5.ad.unc.edu

Remote Server returned ‘550 5.7.64 TenantAttribution; Relay Access Denied [CY4PEPF0000EE33.namprd05.prod.outlook.com 2024-01-14T16:51:49.114Z 08DC14C082F6C312]’

Original message headers:

Received: from relay.unc.edu ( by its-msxhybrid5.ad.unc.edu ( with Microsoft SMTP Server id 15.2.1118.40; Sun, 14 Jan 2024 11:51:48 -0500 Received: from vhost-confluence1.int.ibiblio.org ([]) by relay.unc.edu with Microsoft SMTPSVC(10.0.17763.1697); Sun, 14 Jan 2024 11:51:48 -0500 Received: by vhost-confluence1.int.ibiblio.org (Postfix, from userid 48) id 2A43A20031B; Sun, 14 Jan 2024 11:51:48 -0500 (EST) To: <nein2000@web.de> Subject: 46N 28E submitted From: Rainer Mautz <rainer@mautz.net> Reply-To: <rainer@mautz.net> X-Sender: <rainer@mautz.net> X-Mailer: PHP/7.3.31-1~deb10u5 X-Priority: 3 MIME-Version: 1.0 Content-Type: text/plain; charset=“ISO-8859-1” Content-Transfer-Encoding: 8bit Message-ID: <20240114165148.2A43A20031B@vhost-confluence1.int.ibiblio.org> Date: Sun, 14 Jan 2024 11:51:48 -0500 Return-Path: rainer@mautz.net X-OriginalArrivalTime: 14 Jan 2024 16:51:48.0217 (UTC) FILETIME=[F6D34690:01DA4709]

Please look into why you are using “mail.protection.outlook.com”, and why this is now rejecting outgoing emails

Thanks for the feedback. As a unit within UNC, we are required to use UNC’s infrastructure for outbound mail, and UNC contracts with Microsoft for that service. That is, relay.unc.edu is provided by Microsoft. We will work with the relevant unit(s) of UNC IT to make any needed changes.

We believe the underlying issue was a change in Microsoft policy, and a change has been made to a UNC-managed system that we hope has resolved your issue. Please generate a few test messages and let us know whether or not the change did solve your problem.