SMTP error 458
Unable to queue messages for node — the ETRN failure reply.
Updated Jul 1, 2026
SMTP 458 is the failure reply to the ETRN command, defined in RFC 1985 as "458 Unable to queue messages for node." The relay you asked to flush queued mail could not queue messages for that host, usually because it does not relay for that domain or its queue runner failed. It is transient, so the client may retry ETRN later.
Confirm the relay serves that node; retry ETRN later.
What it means
458 is the negative response to ETRN. That command (RFC 1985) lets a client ask a relay to start processing queued mail for a particular host, typically used by a mail server on an intermittent connection asking its upstream relay to flush whatever is waiting. When that cannot be done, the server answers "458 Unable to queue messages for node". This is narrow: 458 is not a generic "message rejected" or "connection refused", and it has nothing to do with firewalls, antivirus, or your client port or auth settings. It only appears in response to an ETRN command. Its sibling 459 ("Node not allowed") is the policy-refusal variant.
Common causes
The node argument must be a fully qualified domain the server actually relays for. If it is not a secondary or backup MX for that domain, it has nothing to queue and returns 458.
A transient local condition where the server failed to spawn or hand off to its delivery process for that node.
Something on the relay prevented it from scheduling the flush right now.
How to fix it
- Confirm ETRN is the right tool and the node is correct
458 only comes from ETRN. Make sure the node is the exact fully qualified domain the relay holds mail for, not a user address or a bare hostname.
- Verify the server relays for that domain
On the relay side, check that it is a backup or secondary MX for the node and that its relay tables include that domain. If it is not, fix the relay configuration rather than retrying.
- Inspect the relay queue and mail logs
Look at the logs at the moment of the ETRN to see why the queue runner failed (resource limits, a stuck delivery process, spool permissions).
- Retry after a delay
Since 458 is transient, wait and reissue ETRN. If it then succeeds, the original cause was a temporary local error on the relay.
Common questions
Is 458 a permanent failure?
No. It is a transient reply, so the condition is temporary and the client may reissue the ETRN command later.
What is the difference between 458 and 459?
458 means the relay could not queue mail for the node right now (often a temporary or config issue). 459 is a policy refusal: the relay will not serve that node at all.
Does 458 happen during normal email sending?
No. It belongs to relay-to-relay queue management via ETRN, not to ordinary MAIL FROM / RCPT TO / DATA delivery.