Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Sat, 11 Oct 2025 12:38:14 GMT

The original message was received at Sat, 11 Oct 2025 12:38:14 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 [AMS0EPF0000019B.eurprd05.prod.outlook.com 2025-10-11T12:38:14.502Z 08DE07FBF5A744EC])

   ----- 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 [AMS0EPF0000019B.eurprd05.prod.outlook.com 2025-10-11T12:38:14.502Z 08DE07FBF5A744EC]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [AMS0EPF0000019B.eurprd05.prod.outlook.com 2025-10-11T12:38:14.502Z 08DE07FBF5A744EC]