Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Sun, 25 May 2025 13:47:33 GMT

The original message was received at Sun, 25 May 2025 13:47:31 GMT
from m0218248.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 [DU6PEPF00009524.eurprd02.prod.outlook.com 2025-05-25T13:47:33.197Z 08DD9B61EAF47C4F])

   ----- Transcript of session follows -----
... while talking to sudler-com.mail.protection.outlook.com.:
>>> DATA
<<< 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [DU6PEPF00009524.eurprd02.prod.outlook.com 2025-05-25T13:47:33.197Z 08DD9B61EAF47C4F]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [DU6PEPF00009524.eurprd02.prod.outlook.com 2025-05-25T13:47:33.197Z 08DD9B61EAF47C4F]