Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Sun, 7 Dec 2025 07:11:05 GMT

The original message was received at Sun, 7 Dec 2025 07:11:04 GMT
from m0223511.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 [DB1PEPF000509E8.eurprd03.prod.outlook.com 2025-12-07T07:11:05.284Z 08DE344318E827FA])

   ----- 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 [DB1PEPF000509E8.eurprd03.prod.outlook.com 2025-12-07T07:11:05.284Z 08DE344318E827FA]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [DB1PEPF000509E8.eurprd03.prod.outlook.com 2025-12-07T07:11:05.285Z 08DE344318E827FA]