Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Thu, 30 Oct 2025 17:53:57 GMT

The original message was received at Thu, 30 Oct 2025 17:53:56 GMT
from m0424592.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 [DB1PEPF000509E4.eurprd03.prod.outlook.com 2025-10-30T17:53:56.644Z 08DE13921D54EFB3])

   ----- Transcript of session follows -----
... while talking to sgrailing-no.mail.protection.outlook.com.:
>>> DATA
<<< 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [DB1PEPF000509E4.eurprd03.prod.outlook.com 2025-10-30T17:53:56.644Z 08DE13921D54EFB3]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [DB1PEPF000509E4.eurprd03.prod.outlook.com 2025-10-30T17:53:56.644Z 08DE13921D54EFB3]