The 550 5.7.23 bounce means your email failed SPF validation — the sending IP is not authorised in your SPF record. Learn how to fix SPF and stop this bounce.
5.7.23
| Component | Value | Meaning |
|---|---|---|
| Class | 5 | Permanent failure |
| Subject | 7 | Security or policy |
| Detail | 23 | SPF Validation Failed |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
Your email failed SPF validation. The receiving server checked your domain's SPF record and found the sending IP address is not authorised to send on behalf of your domain.
Google returns 5.7.23 specifically for SPF hard fails (-all rejection). With ~all (softfail), Google may still accept but DMARC may fail.
📖 Google Workspace / Gmail documentation →These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
550 5.7.23 The message was rejected because of SPF validation failure
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 →Paste your full NDR email, SMTP error line, or mail log fragment to get an instant plain-English diagnosis.
Open the Bounce Decoder →