What this code means
An error occurred while SPF was evaluated for the arriving message, so the current attempt ended in a temporary failure. A controlled retry is appropriate, not unlimited retries.
Technical meaning
The X.7.24 pattern means that SPF evaluation relative to an arriving message resulted in an error. The standard provides this code in place of 4.4.3 or 5.5.2 for the cases described in Sections 8.6 and 8.7 of RFC 7208. In the concrete 4.7.24 code, the leading digit assigns the result to the temporary class.
Delivery status
The leading digit 4 denotes a persistent transient failure: the current attempt failed, but the condition may clear. The code alone identifies neither the cause of the SPF evaluation error, its duration, nor a permanent problem with the recipient address.
- Class
- Temporary failure
- Retry
- Controlled retry
- Suppression
- Check the full context
Retry decision
Operational recommendation: check suppression before every attempt, retain the full response, and retry with backoff, jitter, idempotency, and a time or attempt limit. Stop after success, a permanent result, a suppression-state change that makes the recipient ineligible, or exhaustion of the limit; refer repeated 4.7.24 results for diagnosis.
Suppression decision
Operational recommendation: do not add the recipient address to a suppression list based on temporary code 4.7.24 alone, because it describes an SPF evaluation error rather than proving that the recipient address is invalid. Inspect the full response, event scope, bounded-retry outcomes, and other delivery signals; suppress only after an independent permanent signal or when the applicable policy requires it.
Common causes
- SPF evaluation for the arriving message resulted in an error; the code alone does not identify the technical condition that caused it.
Diagnostic steps
- Inspect the raw SMTP response or delivery report and confirm the exact code 4.7.24 and a basic reply in the 4xx class; retain the complete response text.
- Correlate the result with the intended message, attempt time and stage, sender identity, and server that returned the code.
- Use available logs from the SPF-evaluating system and supporting services to establish the actual error; do not infer its cause from the code alone.
- Check suppression before the next attempt and compare the bounded retry result; stop after success, a permanent result, or exhaustion of the limit.
Actions by owner
Sender
- Confirm that the message and sender identity used are intended, then give the sender administrator the full response and attempt time without repeatedly retrying it manually.
- Do not change SPF configuration based on the code alone; perform only confirmed corrective actions and report the controlled attempt's outcome.
Sender administrator
- Retain the full response, correlate it with the message, sender identity, and receiving endpoint, check suppression, and route the send through a bounded retry mechanism.
- Inspect available sender-side configuration and logs, then establish the confirmed cause with the recipient administrator or provider before making a change.
Recipient administrator
- If you manage the server that returned the code, inspect its SPF-evaluation and supporting-service logs for the specified time, message, and sender identity.
- Clear the confirmed temporary condition within your control, then verify one controlled attempt and return a precise code.
Provider
- If you operate a service involved in SPF evaluation, inspect managed logs and service state for the specified time and event scope.
- Clear the confirmed temporary condition in the managed layer, or give the appropriate administrators safe, precise diagnostic context.
Sources and verification
The canonical meaning of X.7.24, its use for an SPF evaluation error, and its class assignment were verified against the IANA registry and RFC 2034, RFC 5248, RFC 7208, and RFC 7372 as of July 17, 2026. Retry, suppression, diagnostic, and owner-action guidance is presented separately as operational advice; this record contains no provider-specific practice.
- iana-smtp-enhanced-status-codesT0 source
Enumerated Status Codes / X.7.24
- rfc5248T0 source
Section 2.1: registry fields and non-exclusive Associated Basic Status Code
- rfc2034T0 source
Section 4: enhanced status class agrees with SMTP reply class
- rfc7372T0 source
IANA registry reference for X.7.24
- rfc7208T0 source
IANA registry reference for X.7.24
Last verified:
