How do I fix the 421 5.3.2 bounce error?

Your mail server will retry automatically If the issue persists beyond 24 hours, contact the recipient through another channel If this is your own server, check your mail server configuration

Bounce Decoder: 421 5.3.2

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421 5.3.2 — System Not Accepting Messages

The 5.3.2 SMTP error means the receiving mail system is not currently accepting messages. Learn when this is permanent vs. temporary.

🔴

Permanent Failure (Hard Bounce)

SMTP Code
421

Enhanced Code
5.3.2

Category
System Not Accepting Messages

Frequency
Common

🔢 Enhanced Status Code Breakdown: `5.3.2`

Component	Value	Meaning
Class	5	Permanent failure
Subject	3	Mail system status
Detail	2	System Not Accepting Messages

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

💬 What This Error Means

The receiving mail server is configured to not accept network messages, either permanently or for an extended period. This is typically a server-side shutdown or maintenance decision.

Common Causes

Mail server deliberately shut down or taken offline
Server configured to reject all incoming connections
Network-level block preventing delivery

How to Fix This

Your mail server will retry automatically
If the issue persists beyond 24 hours, contact the recipient through another channel
If this is your own server, check your mail server configuration

📋 Real-World Example Messages

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

421 5.3.2 System not accepting network messages

🔗 Related Error Codes

                    421 4.3.2                

System Not Accepting Mail

                    550 5.3.0                

Other Mail System Status

📚 Official Documentation

↗ RFC 3463 — Enhanced Status Codes

🔍

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