Delivery time expired — message queued too long without delivery
Production Risk
High — a 4.4.7 indicates a serious delivery failure; the message was never received by the intended recipient.
The message has been in the sending MTA's queue for longer than the configured maximum queue lifetime without being successfully delivered. The sending MTA is giving up and generating a bounce notification.
- 1The destination server has been unreachable for an extended period.
- 2All delivery attempts over the queue lifetime have failed with transient errors.
- 3DNS resolution for the destination domain failed persistently.
Sent message that could not be delivered; MTA queue lifetime (typically 4-5 days) has been exceeded.
# DSN bounce message to sender: Subject: Delivery Status Notification (Failure) Your message to user@example.com could not be delivered. Final-Recipient: rfc822; user@example.com Status: 4.4.7 Diagnostic-Code: smtp; 450 4.4.7 Message expired after X delivery attempts
expected output
DSN with status 4.4.7
Fix
Investigate why the destination was unreachable
WHEN After receiving a 4.4.7 bounce
# Check if destination MX is currently reachable:
dig MX example.com
telnet $(dig MX example.com +short | sort -n | head -1 | awk '{print $2}') 25
# Review MTA logs for all retry attempts:
grep 'example.com' /var/log/mail.log | grep -E '(connect|timeout|refused)'Why this works
Understanding why delivery failed repeatedly helps determine whether to resend or treat as a permanent failure.
✕ Immediately resend the message after a 4.4.7 without investigating
If the destination was unreachable for days, the underlying issue may still persist. Investigate before resending.
RFC 3463 — Enhanced Mail System Status Codes
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