MailFixIt

Generic SMTP delivery response

Understand SMTP 4.7.0: Temporary policy or security failure

A temporary security or policy condition blocked this attempt, but the enhanced code does not state which one.

Problem description

A representative response is:

451 4.7.0 Temporary policy or security failure.
Is this temporary or permanent?

Keep normal retries with backoff, but investigate the full text before changing authentication, content, reputation, or access policy.

What this response means

Standard 4.7.0 means an otherwise unspecified temporary security or policy failure. It can accompany very different messages about authentication, content, access rules, rate limits, or reputation.

What to do

  1. Keep the full response, provider hostname, timestamp, sender, recipient, and connecting IP.
  2. Let the sending server retry with increasing delays.
  3. Follow the named cause in the response: fix authentication only when it names SPF, DKIM, or DMARC; fix content only when it names content; reduce traffic only when it names rate or reputation.
  4. Check for a compromised account or sudden traffic change before increasing volume.
  5. If the text remains vague and the deferral persists, submit the evidence to the receiving provider.

Do not rotate DNS records or IP addresses simply because the code belongs to the security class.

What MailFixIt can check

MailFixIt can inspect public DNS authentication when the response makes it relevant. It cannot reproduce a provider’s historical policy or reputation decision.

Choose a related provider-specific page by the complete response text, not by 4.7.0 alone.

Frequently asked questions

What does SMTP 4.7.0: Temporary policy or security failure mean?

A receiver temporarily blocked the message for an unspecified security or policy reason. The human-readable response and provider identify the actual cause.

Can MailFixIt prove this entire bounce from public DNS?

No. The current checker can evaluate selected public DNS configuration, but it cannot recreate recipient state, credentials, reputation, message content, or a historical provider SMTP decision.

Related email diagnostics

SMTP 550 5.7.26: Multiple authentication checks failedUnderstand SMTP 5.7.26 and separate SPF, DKIM, DMARC, and alignment failures before changing email DNS.

Primary sources: IANA SMTP Enhanced Status Codes.