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.
Published · Last verified · Maintained by TamingDNS
534
5.7.9
Authentication Mechanism Too Weak
Common
🔢 Enhanced Status Code Breakdown: 5.7.9
| Component | Value | Meaning |
|---|---|---|
| Class | 5 | Permanent failure (Hard bounce) |
| 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 server requires a more secure way to log in than what was offered. This usually means you need to enable encryption (TLS) or use a more modern authentication method.
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
📚 Official Documentation
📋 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
🔧 Related Diagnostic Tools
These tools can help you diagnose and fix this type of bounce:
🔧 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 →Got a bounce message to decode?
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