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Bounce Decoder: 534 5.7.9

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534 5.7.9 — Authentication Mechanism Too Weak

The 534 5.7.9 error means the SMTP server requires a stronger authentication method. Learn how to upgrade your SMTP auth to fix this error.

🔴
Permanent Failure (Hard Bounce)
SMTP Code
534
Enhanced Code
5.7.9
Category
Authentication Mechanism Too Weak
Frequency
Common

🔢 Enhanced Status Code Breakdown: 5.7.9

Component Value Meaning
Class 5 Permanent failure
Subject 7 Security or policy
Detail 9 Authentication Mechanism Too Weak

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 requires a stronger authentication mechanism than the one your mail server offered. This is usually a configuration issue requiring an upgrade from basic username/password auth.

Common Causes

  • Server requires TLS but connection is unencrypted
  • Server requires SASL mechanisms stronger than PLAIN or LOGIN
  • OAuth 2.0 required but Basic Auth is being used

How to Fix This

  • Enable STARTTLS or TLS in your SMTP configuration
  • Upgrade to OAuth 2.0 authentication if required by the server
  • Contact your email provider for the required authentication settings

📋 Real-World Example Messages

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

534 5.7.9 Please log in with your web browser and then try again

🔗 Related Error Codes

535 5.7.8
Authentication Credentials Invalid
550 5.7.14
Trust Relationship Required

📚 Official Documentation

↗ RFC 3463 — Enhanced Status Codes

🔧 This Bounce Is Related to Email Authentication

Fixing this type of bounce requires correctly configured SPF, DKIM, and DMARC records. Our free Domain Checker analyses all three in one scan and tells you exactly what to fix.

Run a Free Domain Authentication Check →
🔍

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