Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Fri, 10 Oct 2025 09:17:04 GMT

The original message was received at Fri, 10 Oct 2025 09:17:03 GMT
from m0341348.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 [SA2PEPF00003AE7.namprd02.prod.outlook.com 2025-10-10T09:17:04.401Z 08DE0556AEA2E1A3])

   ----- Transcript of session follows -----
... while talking to danaher.mail.protection.outlook.com.:
>>> DATA
<<< 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [SA2PEPF00003AE7.namprd02.prod.outlook.com 2025-10-10T09:17:04.401Z 08DE0556AEA2E1A3]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [SA2PEPF00003AE7.namprd02.prod.outlook.com 2025-10-10T09:17:04.401Z 08DE0556AEA2E1A3]