Why SPF Flattening Is A Must-Have For
Large Or Complex Email Systems

For businesses, especially larger ones with complex email systems, safeguarding email communications is of utmost importance. A vital element of email authentication is the Sender Policy Framework (SPF), which significantly helps reduce threats such as email spoofing and phishing. As companies expand, their SPF records can become increasingly intricate, often including multiple third-party services, making management more challenging and raising the risk of errors. 

This highlights the necessity of SPF flattening. Simplifying SPF records improves security and boosts the likelihood of successful email delivery. So, why is SPF flattening particularly crucial for large or complex email infrastructure.

Understanding SPF and Its Challenges

SPF, or Sender Policy Framework, is a protocol designed for email authentication that verifies if an incoming message comes from a legitimate sender. It accomplishes this by listing authorized IP addresses within a domain's DNS (Domain Name System) records. When an email arrives, the recipient's mail server consults the SPF record to confirm whether the sending server has permission to send emails on behalf of that domain.

In large or intricate email systems, the SPF record often contains references to many third-party services, such as marketing tools, email service providers, and cloud platforms. These references usually manifest as "include" mechanisms that integrate SPF records from other domains. 

The Problem with Complex SPF Records

As an organization's email system expands, the SPF record may become unwieldy due to numerous "include" directives. Each of these directives references another domain's SPF record, which can create multiple layers of lookups. This situation leads to two primary issues:

• Lookup Limit Exceeded: SPF records are limited to 10 DNS lookups. If your SPF record contains more than 10 due to nested includes, it will fail the SPF validation, resulting in the possibility of emails being rejected or categorized as spam.


• Increased Management Complexity: With the rise in third-party email services, maintaining the SPF record becomes increasingly challenging. The process of adding or removing services can introduce mistakes, such as outdated or inaccurate records, which heightens the risk of email delivery problems and potential security threats.

What Is SPF Flattening?

SPF flattening is a method aimed at streamlining intricate SPF records by substituting the "include" directives with the direct IP addresses of external services. This approach minimizes the DNS lookups necessary for email validation, helping to prevent surpassing the lookup threshold.

The process of flattening requires retrieving the SPF records from each third-party service and obtaining their associated IP addresses. These addresses are then incorporated directly into the organization's SPF record, thereby removing the requirement for recursive lookups and keeping the SPF record compliant with the 10-lookup maximum. Click here for further details.

Why SPF Flattening Is a Must-Have for Large or Complex Email Systems

Avoiding Lookup Limit Issues

As noted earlier, SPF records can only accommodate a maximum of 10 DNS lookups. If your email system depends on over 10 external services, you run the danger of exceeding this threshold, which could result in SPF failures and problems with email delivery. To mitigate this risk, you can "flatten" the SPF record by substituting "include" directives with specific IP addresses, ensuring that your record remains within the lookup limit.

Improved Email Deliverability

The success of email marketing and business communications heavily relies on effective email deliverability. When an SPF record is complicated and requires numerous lookups, it heightens the risk of authentication failures. By simplifying the SPF record, we can enhance the efficiency of SPF checks, which helps minimize the likelihood of emails being wrongly classified as spam or blocked by the servers of recipients.

Simplified SPF Record Management

For large organizations, handling SPF records can be quite challenging and prone to mistakes. By flattening the records, you can streamline the process and avoid the hassle of modifying several include mechanisms whenever a third-party service updates its SPF record. This way, you only need to update your own SPF record with the relevant IP addresses, making ongoing management much easier.

The Challenges of SPF Flattening

Although SPF flattening provides many advantages, it also presents some challenges. A major concern is the necessity for continuous oversight. Since third-party services may alter their IP addresses, it’s crucial to regularly refresh your flattened SPF record. Neglecting this can lead to problems with email delivery.

Moreover, flattening eliminates the adaptability of "include" mechanisms. This means that if you switch email providers or introduce additional services, you’ll need to update your SPF record manually. This process can be labor-intensive and demands careful attention.