Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Thu, 15 Jan 2026 11:11:18 GMT

The original message was received at Thu, 15 Jan 2026 11:11:17 GMT
from m0223513.ppops.net [127.0.0.1]

   ----- The following addresses had permanent fatal errors -----
<[email-masked]>
    (reason: 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [DU2PEPF00028D00.eurprd03.prod.outlook.com 2026-01-15T11:11:18.219Z 08DE54129A5C996B])

   ----- Transcript of session follows -----
... while talking to nibe-com.mail.protection.outlook.com.:
>>> DATA
<<< 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [DU2PEPF00028D00.eurprd03.prod.outlook.com 2026-01-15T11:11:18.219Z 08DE54129A5C996B]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [DU2PEPF00028D00.eurprd03.prod.outlook.com 2026-01-15T11:11:18.219Z 08DE54129A5C996B]