From: Mail Delivery Subsystem <mailer-daemon@example.net>
To: sender@example.com
Subject: Final failure
Date: Tue, 02 Jun 2026 10:06:00 +0000
Message-ID: <final-failure@example.net>
Content-Type: text/plain; charset=utf-8

Delivery Status Notification.
Final-Recipient: rfc822; expired@example.com
Action: failed
Status: 5.4.7
Diagnostic-Code: smtp; Could not deliver after retry period. Final failure, giving up.