5.7.0 SMTP bounce: security status

What 5.7.0 means

A security-related policy rejected the message and no more specific security code applies.

Message text

Other or undefined security status

Common causes of 5.7.0

• Receiving-side security policy rejected the message without a more specific code

How to fix 5.7.0

1. Check SPF, DKIM and DMARC with SPF checker, DKIM checker and DMARC checker.
2. Check your sending IP with blocklist check.
3. Read the full bounce text for the detail behind the code.

Check your domain

Check the SPF record of your sending domainRuns in your browser; nothing is uploaded.

Have the full bounce message? Paste it into the bounce code lookup and it will match the code and the provider for you. Open the bounce code lookup.

How to read 5.7.0

The second part, 5.7.0, is an enhanced status code (RFC 3463 §2) written class.subject.detail. Class 5 is a Permanent failure (5xx): the command was rejected and the sender should not repeat it unchanged (RFC 5321 §4.2.1; RFC 3463 §2).. Subject 7 is security or policy: authentication, authorization or policy refused the message. The detail number refines the subject, and providers may define details of their own, which is why one code can read differently at Gmail, Microsoft and Yahoo.

Do not keep resending the same message: a permanent failure repeats until the cause is fixed. Correct the cause, then send a new message.

Official source: www.rfc-editor.org. Last verified 2026-10-20.

Related guides

• How to create an SPF record (syntax and examples)
• How DKIM works and how to publish a DKIM record
• How to set up a DMARC record, from p=none to p=reject

Related codes

• 5.7.1 SMTP: delivery not authorized
• 5.7.23 SMTP: SPF validation failed
• 5.7.25 SMTP: reverse DNS failed
• 5.7.26 SMTP: authentication failed
• 5.7.27 SMTP: sender has null MX
• 550 5.7.26 Gmail: blocked by dmarc policy

FAQ

All bounce codes