421 4.7.28: Blocked: High Complaint Rate
The 421 4.7.28 error is Google-specific and means your domain or IP is blocked due to high spam complaint rates. Learn how to fix your sender reputation.
Published · Last verified · Maintained by TamingDNS
421
4.7.28
Blocked: High Complaint Rate
Very Common
🔢 Enhanced Status Code Breakdown: 4.7.28
| Component | Value | Meaning |
|---|---|---|
| Class | 4 | Temporary failure (Soft bounce) |
| Subject | 7 | Security or policy |
| Detail | 28 | Blocked: High Complaint Rate |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
💬 What This Error Means
Your email reputation has taken a hit. This specific error from Google means that too many people have marked your emails as 'spam' recently. As a result, Google is temporarily blocking your messages to protect its users.
Common Causes
- Recipients are manually clicking the "Report Spam" button on your emails
- You're sending to an old or "cold" list of people who don't remember signing up
- Your email content looks like common spam to Google's automated systems
How to Fix This
- Check Google Postmaster Tools to see your exact spam complaint rate
- Make it incredibly easy for people to unsubscribe so they don't click "Report Spam" instead
- Only send mail to people who have explicitly opted in to hear from you
- Review your email content and avoid "salesy" or aggressive subject lines
📚 Official Documentation
This is a Google-specific code. Your domain or IP reputation is low due to spam complaints. Google Postmaster Tools shows your complaint rate and domain reputation.
📖 Google Workspace / Gmail documentation → Browse all Google Workspace / Gmail error codes →📋 Real-World Example Messages
These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
421-4.7.28 Gmail has detected an unusual rate of unsolicited mail originating from your IP address.
🔗 Related Error Codes
🔧 Related Diagnostic Tools
These tools can help you diagnose and fix this type of bounce:
Got a bounce message to decode?
Paste your full NDR email, SMTP error line, or mail log fragment to get an instant plain-English diagnosis.
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