What this code means
This code may be returned when a message fails ARC validation. It denotes a permanent failure of the current attempt, so do not retry it unchanged.
Technical meaning
The standard X.7.29 pattern may be returned when a message fails ARC validation. In code 5.7.29, the leading digit assigns the result to the permanent-failure class. The code does not identify the cause of the failed validation.
Delivery status
The leading digit 5 denotes a permanent failure of the current attempt. The code confirms a problem with ARC validation, but it does not identify the precise condition or the party responsible for it.
- Class
- Permanent failure
- Retry
- Do not retry unchanged
- Suppression
- Check the full context
Retry decision
Operational guidance: stop automatic and manual retries of the same unchanged attempt. Consider a new, controlled attempt only after establishing the cause, making a confirmed correction, and checking ARC validation and suppression again.
Suppression decision
Operational guidance: do not automatically suppress the recipient address or domain based on 5.7.29 alone. Inspect the complete response, event scope, available ARC validation results, and delivery history, then base the suppression decision on the confirmed cause and applicable policy.
Common causes
- The message failed ARC validation; the code alone does not identify the precise condition that caused the failure.
Diagnostic steps
- Inspect the raw SMTP response or nondelivery report and confirm the exact 5.7.29 code and a basic reply in the 5xx class; retain the complete response text.
- Correlate the response with the intended message, attempt time and stage, and system that returned the code.
- Use available ARC validation results, logs, and configuration to establish the actual failure condition; do not infer its cause or responsible party from the code alone.
- Stop unchanged retries. After a confirmed correction, check ARC validation and suppression again, then make at most one controlled attempt.
Actions by owner
Sender
- Do not manually retry the same unchanged message; give the sender administrator the complete response and attempt time.
Sender administrator
- Retain the complete response, correlate it with the intended message, and inspect available ARC validation results, logs, and configuration to establish the confirmed cause.
- Make only a confirmed correction, check ARC validation and suppression again, and verify the outcome with one controlled attempt.
Recipient administrator
- If you manage the system that returned the code, inspect its ARC validation logs and configuration for the specified attempt; correct a confirmed receiving-side problem or safely give the sender the context needed for remediation.
Provider
- If you operate a managed layer involved in ARC validation, inspect its logs and configuration, correct a confirmed problem in that layer or give the appropriate administrators precise diagnostic context, and do not trigger suppression from the code alone.
Sources and verification
The standard meaning of X.7.29 and its class-5 application were verified against the IANA registry and RFC 2034, RFC 5248, and RFC 8617 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.7.29
- 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
- rfc8617T0 source
IANA registry reference for X.7.29
Last verified:
