Email Knowledge Bounce codes

5.7.0 — Policy rejection (general)

The enhanced status code 5.7.0 is a general “policy” failure. It means the receiving side refused the message based on rules or trust decisions. The exact reason is usually not the number itself, but the diagnostic wording next to it.

What 5.7.0 means

“Policy” is a broad bucket: authentication issues, sender reputation, content filters, attachment rules, or explicit block decisions. Some providers use 5.7.0 when they don’t want to reveal a more specific detail, or when multiple checks contributed to the result.

If you can capture the bounce’s Diagnostic-Code line, do it. Words like “blocked”, “spam”, “not permitted”, “policy”, “authentication”, or “reputation” usually tell you which direction to investigate first.

What it can look like

Action: failed
Status: 5.7.0
Diagnostic-Code: smtp; 550 5.7.0 Message rejected due to policy

Next steps (fast path)

Start with identity and consistency. Make sure the domain you show in From: aligns with your authentication results. Then look at sending patterns (sudden spikes can trigger policy systems) and check whether the message content contains risky elements such as suspicious links, uncommon attachments, or “phishy” wording.

If your bounces are specifically 5.7.1, that often points to authorization/authentication or “local policy” wording. If you see temporary versions (4.7.x), it may be throttling or greylisting.

The most common next page after 5.7.0 is 5.7.1.

Related codes

5.7.1 (policy / not authorized), 4.7.1 (temporary deferral), and the full list: /bouncecodes/.