SMTP code 5.1.2
What the knowledge base's own tables say about this code, and which articles say it — a description of the reply, never a placement prediction.
- Meaning
- The address does not exist, cannot be routed, or has gone
- Next step
- Hard bounce: suppress immediately. Repeated 5.1.1s are also how providers detect stale lists
From SMTP Enhanced Status Codes (RFC 3463) · Using the codes for bounce classification