What this code means
The message was returned because of a security-related problem, but the response does not describe it more precisely. The leading digit 4 denotes a temporary failure, so delivery may be retried in a controlled way.
Technical meaning
The X.7.0 pattern means that the message was returned because of a security-related condition that cannot be properly expressed by another available detail code. The code may also be used when an applicable security policy prevents the condition from being described more precisely. In the concrete 4.7.0 code, the leading digit assigns the result to the transient 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 a particular security mechanism, policy rule, responsible party, nor the condition's duration, and it does not establish that the recipient address is invalid.
- Class
- Temporary failure
- Retry
- Controlled retry
- Suppression
- Check the full context
Retry decision
Operational recommendation: check suppression state before every attempt, then 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 4.7.0 results for diagnosis instead of retrying indefinitely.
Suppression decision
Operational recommendation: do not add the address to a suppression list based on temporary code 4.7.0 alone. Inspect the full response, security context available for the attempt, bounded-retry history, and other delivery events; suppress only after an independent permanent signal or when the applicable policy requires it.
Common causes
- A temporary security-related condition caused the message to be returned, but the reporting system could not describe it with a more specific available code.
- An applicable security policy may have prevented the system from disclosing a more precise description of the condition.
Diagnostic steps
- Inspect the raw SMTP response or delivery report and confirm that the enhanced code is exactly 4.7.0 and that the basic reply is in the 4xx class.
- Correlate the response with the intended message, attempt time, transaction stage, and system that returned the code; retain the full response text and available security context because the code itself is general.
- Inspect available logs to determine whether the system recorded a more specific X.7.x condition or intentionally limited detail under its security policy; do not assign a specific cause from 4.7.0 alone.
- Check suppression before the next attempt, compare bounded-retry outcomes, and stop after success, a permanent result, a recipient-eligibility change, or exhaustion of the configured limit.
Actions by owner
Sender
- Confirm that the send was intended and that the recipient should still receive the message; give the sender administrator the attempt time and available context without repeatedly retrying it manually.
- Do not change credentials or security settings based on the code alone; follow only a confirmed administrator instruction and report the outcome of the new, controlled attempt.
Sender administrator
- Retain the raw response, time, transaction stage, and system that returned the code, check suppression, and then route the message through a bounded retry mechanism with backoff and idempotency.
- Group repeated 4.7.0 results by remote system and time; after the limit is exhausted, stop retrying and give the collected context to the recipient administrator or provider without suppressing based on this code alone.
Recipient administrator
- If the code came from a recipient system you manage, inspect its security and policy logs for the specified time and attempt to identify a more precise condition when policy permits disclosure.
- Clear the confirmed temporary condition within your control and verify the result of a new, controlled attempt; when safe, preserve a more specific status code in the response.
Provider
- If you operate a system involved in the attempt, inspect managed-service logs and the security rules applied at the specified time; do not assign a particular cause from the code alone.
- Clear the confirmed temporary condition in the managed layer and, when policy permits, return a more specific X.7.x code instead of general 4.7.0.
Sources and verification
The canonical T0 meaning of X.7.0 and its class assignment were verified against the IANA registry and RFC 2034, RFC 3463, and RFC 5248 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.7.0
- 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
- rfc3463T0 source
IANA registry reference for X.7.0
Last verified:
