Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Thu, 2 Oct 2025 09:24:44 -0500

The original message was received at Thu, 2 Oct 2025 09:24:43 -0500
from m0001722.ppops.net [127.0.0.1]

   ----- The following addresses had permanent fatal errors -----
<[email-masked]>
    (reason: 550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup)

   ----- Transcript of session follows -----
... while talking to [137.169.24.7]:
>>> DATA
<<< 550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.5.2 Need rcpt command