The Sender Requirements Failure Report helps organizations quickly identify issues impacting message delivery by providing detailed visibility into mail failures. The report surfaces key diagnostic data - including error codes, authentication results, and source-level details. This report makes it easier to investigate and address sending issues across your domains, and meet Google’s Sender Requirement Guidelines.
Valimail customers can now view these error codes using the new Sender Requirements Failure Report in Monitor and Enforce.
This report provides:
Visibility into Google's new SMTP error codes, which explain why Gmail may have taken action on your mail
Context and reference details for each error, including authentication results and related domain or IP information
Diagnostic insights to help identify potential authentication or infrastructure issues impacting message delivery
Overview Page
The Overview page provides a high-level summary of your domain's failures.
What you’ll see:
Total Failure Count across the selected date range
Graph of failure types over time to track trends
Pie chart showing distribution of failure types
Top 3 customer issues with associated failure counts
You can view Google’s full list of SMTP error codes here.
Failure Codes Page
This page provides a detailed view of each unique error code observed, including:
Error Code | Description | Total Messages |
421-4.7.30 | Rate limiting due to failed DKIM authentication | 113,928 |
550-5.7.25 | Blocked due to missing or mismatched PTR record | 3,784 |
550-5.7.1 | Blocked due to spam, reputation, or RFC 5322 issues | 21 |
Each error code includes a "Details" link to drill down further.
Error Code Detail Page
Clicking into a code opens a detailed breakdown showing:
Affected source IPs
Affected sending domains
SPF, DKIM, and DMARC pass/fail status
Date of occurrence
Bulk sender requirements tags (Gmail-related)
Resolution guidance
Example:
Error: 421-4.7.30
Explanation: Gmail limited your email because your domain isn’t set up with DKIM.
Recommendation: Set up DKIM signing on your domain and verify proper configuration.
Domains Page
This section provides a domain-level breakdown of failures.
For each domain, you’ll see:
Total failed messages
Primary issue (e.g., missing DKIM)
The ability to drill down into subdomain-level details and message patterns
Domain | Total Failed Messages | Primary Issue |
exampledomain.com | 116,205 | DKIM missing |
demo-mail.net | 1,486 | DKIM missing |
testdomain.org | 19 | PTR issue |
samplecorp.co | 1 | RFC 5322 compliance |
These are sample domains shown for illustrative purposes only. Your actual data will reflect your organization’s sending domains and observed issues.
Common Error Codes
Below is a list of the most commonly observed error codes across customer traffic today. These codes indicate why Gmail may have taken action on specific messages:
Code | Meaning |
421-4.7.27 | Rate limiting due to SPF failure |
421-4.7.29 | Rate limiting due to lack of TLS |
421-4.7.30 | Rate limiting due to failed DKIM authentication |
421-4.7.32 | Rate limiting due to lack of alignment |
550-5.7.1 | Blocked due to spam, reputation, or RFC violations |
550-5.7.25 | Blocked due to missing/mismatched PTR record |
550-5.7.27 | Blocked due to SPF failure |
550-5.7.29 | Blocked due to lack of TLS |
550-5.7.30 | Blocked due to failed DKIM authentication |
550-5.7.40 | Blocked due to message content or policy violation |
These represent the current scope of codes surfaced in the Sender Requirements Failure Report.
As Google continues to expand its use of SMTP error codes, we expect the list of observed codes to grow over time. For a full and up-to-date reference, see Google’s official SMTP error code documentation.
These diagnostics help email administrators quickly identify and resolve:
SPF failures
DKIM failures
Alignment issues
PTR/reverse DNS mismatches
RFC 5322 compliance issues
The Sender Requirements Failure Report provides visibility into why Gmail may be taking action on your messages, based on Google’s SMTP error codes. While it doesn't directly resolve deliverability issues, it highlights key signals to help guide your investigation. For further questions or assistance, please reach out to Valimail Support.