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SMTP Bounce Code 5.7.0: Security Status (Other)

SMTP bounce code 5.7.0 indicates that the message was rejected due to a security or policy issue that doesn't fall into a more specific category. This is a permanent failure (rejection) that requires investigation into your email authentication, content, or sender reputation.

What Does 5.7.0 Mean?

The enhanced status code 5.7.0 follows the SMTP Enhanced Status Code format:

  • 5 = Permanent failure (hard bounce)
  • 7 = Security or policy status
  • 0 = Other or undefined security status

When you receive a 5.7.0 bounce, it means the receiving mail server has blocked your email due to security concerns, but the specific reason isn't categorized under a more specific code like 5.7.1 (delivery not authorized). This is a catch-all code for various security-related rejections.

Bounce Type

  • Type: Rejection (permanent failure)
  • Category: Content/Auth
  • Action Required: Review email authentication, content, sender reputation, and security policies

Common Causes

  1. General Security Policy Violation: The email violates the recipient's security policies without a specific reason
  2. Content Security Issues: The email content triggers security filters (malware, phishing, suspicious links)
  3. Sender Reputation: Your sending IP or domain has a poor reputation that triggers security filters
  4. Authentication Problems: General authentication issues that don't fit specific categories
  5. Policy Restrictions: The recipient's organization has policies that block your emails
  6. Spam Filtering: Advanced spam filters have flagged your email as suspicious
  7. Rate Limiting: You've exceeded rate limits, triggering security measures
  8. Blacklist Status: Your IP or domain is on a security blacklist
  9. Content Analysis: The email content has been flagged by content analysis systems
  10. Unknown Security Issue: A security concern that doesn't fit into standard categories

How to Resolve

For Email Marketers

  1. Review Email Authentication: Ensure SPF, DKIM, and DMARC are properly configured:
    • Verify SPF records include all sending IPs
    • Check DKIM signing is enabled and valid
    • Review DMARC policy configuration
  2. Check Sender Reputation: Investigate your IP and domain reputation:
    • Use Sender Score to check IP reputation
    • Check Google Postmaster Tools for domain reputation
    • Review Microsoft SNDS for Outlook/Hotmail reputation
  3. Review Email Content: Analyze your email content for issues:
    • Avoid spam trigger words
    • Ensure proper text-to-image ratios
    • Include clear unsubscribe links
    • Avoid suspicious link patterns
  4. Check Blocklists: Verify you're not on major security blocklists:
    • Spamhaus
    • Barracuda
    • SURBL
    • SpamCop
  5. Review Sending Practices: Ensure you're following best practices:
    • Maintain low bounce rates (<2%)
    • Keep complaint rates low (<0.1%)
    • Use double opt-in
    • Clean your email lists regularly
  6. Contact Recipient: If possible, contact the recipient's IT department to understand their security policies

For Developers

  1. Implement Comprehensive Authentication: Set up SPF, DKIM, and DMARC properly
  2. Monitor Authentication Rates: Track SPF, DKIM, and DMARC pass rates
  3. Log Security Bounces: Track 5.7.0 bounces to identify patterns
  4. Implement Rate Limiting: Control sending rates to avoid triggering security measures
  5. Content Analysis: Review email content for potential security triggers
  6. Reputation Monitoring: Set up automated monitoring of sender reputation
  7. Blocklist Checking: Implement automated blocklist checking

Security Checklist

  • SPF records are properly configured
  • DKIM signing is enabled and valid
  • DMARC policy is configured
  • Reverse DNS (PTR) records are set up
  • Sender reputation is good
  • Not on any major blocklists
  • Email content follows best practices
  • Unsubscribe links are present
  • Sending rates are within limits
  • Bounce and complaint rates are low

Related Bounce Codes

Examples

Example Bounce Message

550 5.7.0 Security status
Message rejected due to security policy.

Example Enhanced Status Code

550 5.7.0 <[email protected]>: Message rejected due to security policy

Common Email Provider Responses

  • Gmail: "Message rejected due to security policy"
  • Outlook/Hotmail: "550 5.7.0 Security status"
  • Enterprise: "Message blocked by security policy"
  • Custom: "Security violation detected"

Best Practices

  1. Always Authenticate: Never send emails without proper SPF, DKIM, and DMARC configuration
  2. Monitor Reputation: Regularly check your sender reputation and address issues promptly
  3. Follow Best Practices: Adhere to email marketing best practices and legal requirements
  4. Test Before Sending: Use email testing tools to verify authentication and content
  5. Respond Quickly: If you notice security bounces, investigate and fix issues immediately
  6. Maintain List Hygiene: Keep your email list clean to avoid security concerns
  7. Document Policies: Understand and comply with recipient organization policies
  8. Gradual Scaling: When increasing sending volume, do so gradually to avoid triggering security measures

Investigation Steps

When you receive 5.7.0 bounces, follow these investigation steps:

  1. Check Authentication: Verify SPF, DKIM, and DMARC are passing
  2. Review Reputation: Check IP and domain reputation scores
  3. Check Blocklists: Verify you're not on any blocklists
  4. Analyze Content: Review email content for potential triggers
  5. Check Rates: Verify you're not exceeding rate limits
  6. Review Metrics: Check bounce and complaint rates
  7. Contact Support: Reach out to the recipient's IT department if needed