MailFixIt

Generic SMTP delivery response

Understand SMTP 4.7.1: Temporary authorization or policy rejection

The receiver temporarily refused delivery under an access or filtering policy, but the text after the code is needed to identify that policy.

Problem description

A representative response is:

451 4.7.1 Delivery temporarily not authorized under receiver policy.
Is this temporary or permanent?

The 4.x class is temporary. Retry with backoff while correcting any specific cause named by the receiver.

What this response means

Receivers commonly use 4.7.1 for a temporary policy or authorization deferral. IANA defines the X.7.1 subject as delivery not authorized, while the leading 4 says this particular attempt is retryable. Provider wording determines the practical cause.

What to do

  1. Preserve the complete response, receiver hostname, timestamp, sender, recipient, and connecting IP.
  2. Keep normal retries with backoff; do not retry aggressively.
  3. If the response names greylisting, let the same responsible mail route retry later.
  4. If it names authentication, reputation, content, or an allow/block rule, correct only that specific issue.
  5. If it persists without a clear cause, ask the receiving provider or recipient administrator which policy matched.

A DNS change is justified only when the full response identifies a DNS or authentication problem.

What MailFixIt can check

MailFixIt can inspect relevant public authentication records. It cannot prove receiver allowlists, content filters, or reputation state.

Use the provider-specific page that matches the full bounce text whenever one is available.

Frequently asked questions

What does SMTP 4.7.1 temporary authorization or policy rejection mean?

The receiver temporarily refused the message under a security or delivery-authorization policy. The code alone does not reveal which policy matched.

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.