5.7.23SPF validation produced a fail result

The receiving system permanently rejected the message because its SPF check produced a fail result contrary to local policy. Do not retry the same unchanged attempt.

The standard X.7.23 pattern means that a message completed an SPF check that produced a fail result contrary to local policy requirements. Under Section 8.4 of RFC 7208, this code is used instead of 5.7.1. Code 5.7.23 applies this detail in the permanent-failure class.

The leading digit 5 denotes a permanent failure of the current attempt. The code confirms the SPF fail result and conflict with local policy, but it does not by itself identify the cause of that result, the layer responsible, or any particular provider's policy.

Class

Permanent failure

Retry

Do not retry unchanged

Suppression

Check the full context

Operational guidance: stop automatic and manual retries of the same unchanged attempt. Consider a new, controlled attempt only after a confirmed correction or confirmed change in policy conditions and verification that SPF no longer produces a fail result; check suppression again first.

Operational guidance: do not automatically suppress the recipient address or domain based on 5.7.23 alone. Inspect the complete response, SPF result, event scope, configuration of the systems involved, and delivery history, then make the suppression decision according to the confirmed cause and applicable policy.

• The message's SPF check produced a fail result that was contrary to the receiving system's local policy requirements.

1. Inspect the raw SMTP response or nondelivery report and confirm the exact 5.7.23 code and a basic reply in the 5xx class; retain the complete response text.
2. Correlate the response with the intended message, attempt time and stage, evaluated sender identity, and system that returned the code.
3. Use available authentication results, logs, and configuration to confirm the SPF fail result and establish its actual cause; do not assign responsibility or provider practice from the code alone.
4. Stop unchanged retries. After a confirmed correction or change in conditions, verify that SPF no longer produces a fail result, check suppression again, and make one controlled attempt.

A verified provider example for 5.7.23 appears below, from Rackspace Email. It shows real provider practice for this response and does not redefine the standard 5.7.23 meaning or cover every occurrence.

550 5.7.23 The message was rejected because of Sender Policy Framework violation

Compare 2.7.0 and 4.7.0 for other or undefined security statuses in the success and temporary-failure classes, respectively, 4.7.1 for a temporary refusal of unauthorized delivery, and 4.7.12 for a required authentication-mechanism transition. None denotes a permanent rejection because an SPF fail result conflicted with local policy.

• 2.7.0Other or undefined security status (success)
• 4.7.0Other or undefined temporary security status
• 4.7.1Delivery not authorized, message temporarily refused
• 4.7.12Authentication mechanism transition required

The canonical Tier-0 meaning of X.7.23, its use instead of 5.7.1 under Section 8.4 of RFC 7208, and its class-5 application were verified against the IANA registry and RFC 2034, RFC 5248, RFC 7208, and RFC 7372 as of July 17, 2026. Diagnostic, remediation, retry, and suppression recommendations are separate operational guidance; this record contains no provider-specific practice.

• iana-smtp-enhanced-status-codesT0 source

  Enumerated Status Codes / X.7.23

• 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.7.23

• rfc7208T0 source

  IANA registry reference for X.7.23

• ext-src-rackspace-5-7-23-01T1 source

  docs.rackspace.com/docs/common-email-bounces > 'SMTP error' table, row SPF-violation

Last verified: 17 July 2026