Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Wed, 25 Jun 2025 15:54:34 GMT

The original message was received at Wed, 25 Jun 2025 15:54:32 GMT
from m0233773.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 [SJ1PEPF000023D8.namprd21.prod.outlook.com 2025-06-25T15:54:34.722Z 08DDB048276256B1])

   ----- Transcript of session follows -----
... while talking to lpc-com.mail.protection.outlook.com.:
>>> DATA
<<< 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [SJ1PEPF000023D8.namprd21.prod.outlook.com 2025-06-25T15:54:34.722Z 08DDB048276256B1]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [SJ1PEPF000023D8.namprd21.prod.outlook.com 2025-06-25T15:54:34.722Z 08DDB048276256B1]