The 550 5.7.26 bounce means your email failed DMARC and was rejected. Learn why DMARC violations happen and how to fix SPF and DKIM alignment.
5.7.26
| Component | Value | Meaning |
|---|---|---|
| Class | 5 | Permanent failure |
| Subject | 7 | Security or policy |
| Detail | 26 | DMARC Policy Violation |
Per RFC 3463 Enhanced Mail System Status Codes. Class (X) = severity, Subject (Y) = category, Detail (Z) = specific condition.
Your email failed DMARC validation and was rejected per the recipient domain's p=reject policy. Both SPF and DKIM alignment failed — neither authenticated with your From: domain.
Google enforces DMARC p=reject strictly. Since 2024 Gmail bulk sender requirements mandate DMARC at minimum p=none.
📖 Google Workspace / Gmail documentation →Microsoft 365 enforces DMARC rejection for inbound email to Office 365 mailboxes.
📖 Microsoft 365 / Outlook documentation →These are real bounce message formats you might receive. Paste yours into the Bounce Decoder for instant analysis.
From: [email protected] Subject: Undeliverable Status: 5.7.26 Diagnostic-Code: smtp; 550 5.7.26 This message does not pass authentication checks (SPF and DKIM both do not pass).
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 →