Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Wed, 21 May 2025 14:09:16 GMT

The original message was received at Wed, 21 May 2025 14:09:14 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 [SJ1PEPF000023D1.namprd02.prod.outlook.com 2025-05-21T14:09:16.211Z 08DD97D5E4355C41])

   ----- 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 [SJ1PEPF000023D1.namprd02.prod.outlook.com 2025-05-21T14:09:16.211Z 08DD97D5E4355C41]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [SJ1PEPF000023D1.namprd02.prod.outlook.com 2025-05-21T14:09:16.211Z 08DD97D5E4355C41]