Skip to main content

​
Introduction

This error occurs when your email has been blocked due to message content that has been flagged by our content filtering system. The [CS] designation indicates that the content within the message body triggered one of our content security policies.

​
Example Error Message

Here’s what this error looks like: 
[email protected]
   host relay.jetsmtp.net [103.173.0.0]
   SMTP error from remote mail server after end of data:
   550 [CS] Blocked. See https://reports.jetsmtp.net/?id=000000000000000000&auth=smtpuser

​
What Does This Mean?

Our content filtering system has identified elements in your email that may pose delivery risks or violate email best practices. This can include:
  • Content patterns that are commonly associated with spam or malicious emails
  • Elements that may trigger recipient spam filters
  • Content that violates industry standards for email communication
  • Material that could impact deliverability across major email providers

​
How to Address This Error

To resolve content-related blocks:
  1. Review your message content: Examine the message body and any attachments
  2. Check for common issues:
    • Excessive use of promotional language
    • Suspicious links or attachments
    • Formatting that resembles spam patterns
    • Content that may be flagged by recipient filters
  3. Modify your message: Revise the content to align with email best practices
  4. Test before sending: Consider using email testing tools to preview how your content might be perceived

​
Content Best Practices

To prevent future content blocks:
  • Use clear, professional language in your communications
  • Avoid excessive use of promotional terms or phrases
  • Ensure all links are legitimate and properly formatted
  • Include proper unsubscribe mechanisms where required
  • Maintain a professional sender reputation through quality content
  • Follow industry standards for email marketing and transactional messaging

​
Getting Help

If you believe your email was blocked in error or need assistance with content guidelines:
  • Contact JetEmail Support with details about your sending practices
  • Provide examples of the content that was blocked (when appropriate)
  • Be prepared to discuss your email creation and sending processes
Note: Content filtering decisions are based on multiple factors and algorithms designed to protect email deliverability. Specific filter criteria are not disclosed to maintain system effectiveness.