Summary

This guide explains how to integrate SPF (Sender Policy Framework) with DuoCircle's DNS and email services. It includes configuration instructions, troubleshooting tips, and recommendations for optimal security. For more information on SPF, refer to the Wikipedia article on Sender Policy Framework.

Objective

By following this guide, you will:

  • Learn to configure SPF records for DuoCircle services.
  • Optimize your email security.
  • Troubleshoot common SPF issues.

Introduction

SPF is a vital email authentication mechanism that helps prevent spoofing and ensures your emails are delivered securely. This guide focuses on configuring SPF records for DuoCircle's Standard SMTP, Email Gateway, and Backup MX services.

Prerequisites

  • Access to your domain's DNS settings.
  • Familiarity with SPF syntax and configuration.
  • Relevant permissions for DNS modifications.

Step-by-Step Instructions

1. Configuring SPF for DuoCircle Standard SMTP

Customers using DuoCircle's Standard SMTP service to send email for their domain can configure an SPF record to authorize DuoCircle's servers.


For specific recommendations on how to configure SPF for each of your sending domains, detailed instructions are provided on the Sending Domains configuration page for your service.

Recommendation: when to use the ~all mechanism instead of the technically-stronger -all?
  • The -all setting rejects email from IPs not explicitly listed in your SPF record.
    DMARC permits mail passing DKIM validation only to pass DMARC
    ...however some receivers may still reject on SPF hardfail with a -all record even if DKIM passes
  • If your domain has an enforcing DMARC record (p=quarantine or p=reject) then it is recommended to use ~all
  • For a deeper dive on why, check out this Mailhardener article

2. Troubleshooting SPF Record Validation

If you receive errors when validating your SPF record:

Consult the Common SPF Verification Problems guide for troubleshooting steps.

3. Addressing SPF Record Limitations

When combining DuoCircle's SPF record with another provider, you may exceed the 10 DNS lookup limit. 

In such cases: Flatten your SPF record as described in this guide.



Conclusion

By configuring SPF for DuoCircle services, you improve email security and reduce spoofing risks. Use the resources provided in this guide to troubleshoot and optimize your SPF configuration effectively.