Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Fri, 27 Jun 2025 15:09:53 +0200

The original message was received at Fri, 27 Jun 2025 15:09:51 +0200
from m0232386.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 [SJ5PEPF000001CD.namprd05.prod.outlook.com 2025-06-27T13:09:52.919Z 08DDB10D5EECA094])

   ----- Transcript of session follows -----
... while talking to flygt-com.mail.protection.outlook.com.:
>>> DATA
<<< 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [SJ5PEPF000001CD.namprd05.prod.outlook.com 2025-06-27T13:09:52.919Z 08DDB10D5EECA094]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [SJ5PEPF000001CD.namprd05.prod.outlook.com 2025-06-27T13:09:52.919Z 08DDB10D5EECA094]