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Bounce Decoder: 421 4.4.1

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421 4.4.1 — No Answer from Host

The 421 4.4.1 soft bounce means the destination mail server is not responding to connections. Learn what causes connection timeouts and when the email will be retried.

🟡
Temporary Failure (Soft Bounce)
SMTP Code
421
Enhanced Code
4.4.1
Category
No Answer from Host
Frequency
Very Common

🔢 Enhanced Status Code Breakdown: 4.4.1

Component Value Meaning
Class 4 Persistent transient failure (temporary)
Subject 4 Network and routing
Detail 1 No Answer from Host

Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.

💬 What This Error Means

The sending server tried to connect to the recipient's mail server but got no response. The destination server may be down, overloaded, or experiencing a network problem. Your mail server will keep retrying.

Common Causes

  • Recipient mail server is temporarily offline
  • Firewall or network issue blocking the SMTP port (25)
  • Server overload causing connection refusals
  • DNS resolved correctly but the server is not responding

How to Fix This

  • Your mail server retries automatically — no action needed
  • If this persists for more than 12 hours, check if the recipient domain is reachable
  • Use our Domain Checker to verify the domain's MX records point to live servers

📋 Real-World Example Messages

These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis. 

421 4.4.1 Connection timed out
421 4.4.1 [x.x.x.x] No answer from host

🔗 Related Error Codes

421 4.4.2
Bad Connection
421 4.4.7
Message Expired in Queue
421 4.3.2
System Not Accepting Mail

📚 Official Documentation

↗ RFC 3463 — Enhanced Status Codes
🔍

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