Mastering SPF Records with Strategies to Circumvent Flattening Pitfalls

Sender Policy Framework (SPF) records are vital in certifying an email's authenticity, helping to prevent spam and phishing by verifying sender IP addresses.

However, the SPF protocol is not without its limitations, most notably the 10 DNS lookup constraint. Exceeding this threshold can lead to legitimate emails failing authentication, propelling organizations towards 'SPF record flattening' as a workaround. But is flattening the right approach, or does it open up a Pandora's box of security risks?

Enhancing SPF Record Best Practices

Flattening, while tempting, is essentially a band-aid solution; it converts dynamic hostnames into static IP addresses to evade DNS lookup limits. Despite its initial appeal, this practice increases the vulnerability of your domain, inadvertently granting permissions to swathes of the internet and creating opportunities for malicious exploitation.

Rather than flattening, the focus should be on refining SPF records to be as lean and effective as possible. Here’s how to refine your SPF practices:

Regularly Audit Your SPF Records

    1. Remove entries for vendors that don’t align with SPF's MAIL FROM domain.
    2. Discontinue using 'a' and 'mx' mechanisms if they serve no clear purpose.
    3. Eliminate duplicate SPF mechanisms to streamline your record.

Embrace Subdomain Segmentation

  1. Assign specific email streams to dedicated subdomains, each with its DNS lookup quota.
  2. Use subdomains to enhance visibility and isolate system/vendor usage.
  3. Maintain consistent traffic volumes to build a stable reputation for each subdomain.

Adopt Restrictive SPF Policies for Non-Senders

  1. Implement a “v=spf1 -all” policy for domains that don’t send emails to deter misuse.
  2. Avoid permissive settings like “+all” or neutral “?all” that weaken your SPF's defensive stance.

4. Synchronize SPF and DMARC Policies:

  1. Align the SPF record's fail policy ("-all" or "~all") with your current DMARC policy phase.
  2. Transition to a stricter SPF fail policy as you progress towards a DMARC 'reject' policy.

5. Develop a Process for SPF Management

  1. Integrate SPF record checks into routine domain maintenance activities.
  2. Ensure changes in third-party vendor relationships are reflected in your SPF record.


While SPF record flattening might appear as a convenient shortcut, the smarter long-term strategy lies in diligent SPF management and strategic segmentation. By embracing best practices and eschewing the quick fixes of flattening, you can ensure robust email authentication and maintain the integrity of your email ecosystem.

Ready to enhance your email security and take control of your SPF management?

Our domain security specialists are equipped to steer you through the complexities of SPF configuration, ensuring your organization's email communication is safeguarded from modern-day cyber threats. Don't leave your email integrity to chance. Reach out today for expert guidance and take a definitive step towards a more secure and trustworthy email ecosystem.