SPF Flattening Vs. Manual Optimization:
Which Is Better For Your Domain?


The Sender Policy Framework (SPF) plays a crucial role in authenticating your emails, safeguarding against domain spoofing, and enhancing email deliverability. Nevertheless, maintaining SPF records can be challenging, particularly when your domain utilizes several third-party services to send emails. A significant obstacle is the 10 DNS lookup limit set by SPF standards. To navigate this issue, companies often turn to either SPF flattening or manual optimization. But which option is more suitable for your domain?

Let's explore both strategies, weigh their advantages and disadvantages, and assist you in deciding which one aligns best with your organization’s needs.


Understanding SPF and the DNS Lookup Limit


What Is SPF?

SPF is an email authentication technique that relies on DNS. It enables domain owners to designate specific mail servers that have permission to send emails for them. When an email is received, the receiving server examines the sender's SPF record to confirm the sender's IP address.


The 10 DNS Lookup Limitation

The SPF protocol limits the total DNS lookups to 10 when assessing an SPF record. Each mechanism, such as "include," "a," "mx," or "redirect," may initiate a DNS query. If this limit is surpassed, it leads to an SPF "PermError," potentially causing valid emails to be rejected during authentication.



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SPF Flattening: The Automated Approach


SPF flattening is an automated process that minimizes or removes DNS lookups by converting all domains and mechanisms into direct IP addresses when the SPF record is created. This assists in avoiding SPF record issues caused by the 10-DNS-lookup restriction.


How SPF Flattening Works

SPF flattening tools analyze your SPF record and systematically resolve all include mechanisms and domain references to their associated IP addresses. These IPs are then incorporated directly into the SPF record through the “ip4” or “ip6” mechanisms.


Benefits of SPF Flattening

  • Prevents DNS Lookup Issues: By reducing or removing lookup processes, you ensure compliance with the 10-lookup restriction.

  • Effortless and Streamlined: Numerous SPF management tools offer automated flattening, significantly decreasing the effort needed to manage records.

  • Enhances Email Deliverability: A simplified SPF record lowers the likelihood of PermErrors, helping your emails avoid being marked as spam or rejected.

Downsides of SPF Flattening

  • Static IP Addresses May Become Obsolete: Should a third-party service alter its IP addresses, your SPF record will not be updated unless you re-execute the flattening procedure.

  • Issues with Record Length: A flattened record containing numerous IPs might surpass the 255-character limit imposed on DNS records.

  • Increased Maintenance Difficulty: To ensure accuracy and effectiveness, flattened records require routine updates. To learn more, all you need to do is click the link.


Manual Optimization: The Hands-On Strategy


How Manual Optimization Works

Administrators carefully examine the SPF record step by step, eliminating redundant includes, streamlining services, and updating ineffective methods. Strategies employed involve:

  • Merging related services into a single include.

  • Eliminating obsolete or unused email services.

  • Utilizing subdomains for distinct email operations.

Benefits of Manual Optimization

  • Ongoing Updates Remain Consistent: External services handle their integrations, ensuring that any alterations in IP addresses are updated automatically.

  • Enhanced Record Organization: Records that are carefully selected can stay streamlined and adhere to DNS size constraints.

  • Clarity and Oversight: You have complete visibility into your SPF record's contents and their purposes, aiding in troubleshooting and audit processes.


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Downsides of Manual Optimization

  • Labor-Intensive: It necessitates specialized knowledge and ongoing maintenance.

  • Increased Chance of Mistakes: A single incorrect inclusion or syntax error can lead to SPF malfunctions.

  • Limited Scalability: For companies utilizing numerous third-party services, handling everything manually can become unwieldy.

Which Is Better for Your Domain?


Choose SPF Flattening If:

SPF flattening is particularly beneficial for domains that depend on numerous third-party email services and may face the risk of surpassing the 10-DNS-lookup limit imposed by SPF. This approach is especially advantageous when there are constraints on time or technical expertise, as flattening tools can streamline the process and alleviate administrative workload.

Companies that favor automated solutions will find value in tools that frequently update flattened SPF records, ensuring they remain accurate with little need for manual effort.


Choose Manual Optimization If:

Manual optimization is ideal for situations with limited third-party integrations, where it's feasible to keep DNS lookups within acceptable limits without relying on automation. This technique is particularly beneficial when timely updates from email service providers are crucial, as manually maintained records using include will automatically accommodate any IP changes from those providers. 

Companies that possess technical skills and prefer to have complete oversight of their SPF settings will appreciate this method for its flexibility and clarity, especially during troubleshooting or auditing SPF-related concerns.