421 4.3.2: System Not Accepting Mail
The 421 4.3.2 soft bounce means the receiving mail server is temporarily unavailable. Learn what causes this and when to retry.
Published · Last verified · Maintained by TamingDNS
421
4.3.2
System Not Accepting Mail
Common
🔢 Enhanced Status Code Breakdown: 4.3.2
| Component | Value | Meaning |
|---|---|---|
| Class | 4 | Temporary failure (Soft bounce) |
| Subject | 3 | Mail system status |
| Detail | 2 | System Not Accepting Mail |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
💬 What This Error Means
The receiving server is 'temporarily closed.' It might be down for maintenance, rebooting, or just too busy to talk right now. This is a soft bounce, and your server will automatically try again in a little while.
Common Causes
- The other mail server is currently undergoing maintenance
- The server is overwhelmed with too many emails at once
- A temporary network problem is blocking the connection
How to Fix This
- Sit back and relax. Your mail server will automatically try to deliver the message again
- If this persists for more than a day, there might be a larger problem on the recipient's side
📚 Official Documentation
📋 Real-World Example Messages
These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
421 4.3.2 Service temporarily unavailable 421 4.3.2 All server ports are busy
🔗 Related Error Codes
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