535 5.7.1
535 5.7.1 SMTP Authentication Failed
Gmail rejected the login attempt because the credentials or authentication method are invalid.
Incorrect passwords, disabled Less Secure Apps, or missing OAuth tokens surface as 535 5.7.1 before any mail is accepted.
Severity
ERROR
Provider
Gmail
Reference
Mitigation Portal
Last Reviewed
2025-06-01
How to Fix 535 5.7.1
Follow these steps to resolve this Gmail SMTP error and restore normal delivery.
- ✓Verify the SMTP username and password or refresh the OAuth token.
- ✓Enable SMTP Authentication for the account inside Google Workspace.
- ✓Use OAuth 2.0 for programmatic access instead of basic auth where possible.
- ✓Check that two-factor authentication is not blocking the connection.
Helpful Resources
More Gmail SMTP Codes
Keep these related troubleshooting guides handy while addressing 535 5.7.1.
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