Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Tue, 11 Nov 2025 11:04:20 +0200

The original message was received at Tue, 11 Nov 2025 11:04:07 +0200
from harmaja.edelkey.net [213.138.147.141]

   ----- 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 [AMS0EPF000001B5.eurprd05.prod.outlook.com 2025-11-11T09:04:20.469Z 08DE1EAEE349F24B])

   ----- Transcript of session follows -----
... while talking to halton-com.mail.protection.outlook.com.:
>>> DATA
<<< 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [AMS0EPF000001B5.eurprd05.prod.outlook.com 2025-11-11T09:04:20.469Z 08DE1EAEE349F24B]
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command [AMS0EPF000001B5.eurprd05.prod.outlook.com 2025-11-11T09:04:20.469Z 08DE1EAEE349F24B]