Exact response pattern
550 5.4.7 Delivery time expiredPermanentGenericQueue
What it means
The message remained queued until its delivery lifetime expired.
Likely causes
- Persistent temporary failures.
- Too-short queue lifetime.
- Unresolved destination outage.
Recommended response
- Review the preceding deferrals.
- Correct the root cause before resending.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.