SPF Flattening Vs. Regular SPF Records:
What’s The Difference?


In the realm of email security, the Sender Policy Framework (SPF) record plays a vital role in safeguarding your domain against phishing schemes and email impersonation. SPF enables email servers to confirm that incoming messages are from legitimate sources by checking the SPF record associated with the sending domain. Nevertheless, managing SPF records can become quite intricate, particularly for extensive email systems that utilize various third-party services. This is where SPF Flattening comes into the picture.

This article will delve into the fundamental distinctions between SPF Flattening and standard SPF records, examine their respective advantages and drawbacks, and offer guidance on which method may be most suitable for your email security requirements.


What is a Regular SPF Record?


An SPF Record, or Sender Policy Framework Record, is a type of text-based DNS (Domain Name System) entry that identifies all the approved IP addresses or domains permitted to send emails on behalf of your domain. Its primary function is to combat email spoofing by enabling recipients to verify whether an email originates from a legitimate source. SPF records can incorporate various mechanisms, including ip4, ip6, include, and all, which delineate authorized senders.



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What is SPF Flattening?


SPF Flattening refers to the method of streamlining an SPF record by minimizing the number of DNS queries needed for its verification. Generally, SPF records can incorporate other SPF records through the use of the include mechanism, which points to the SPF record of a different domain. Each inclusion, however, necessitates an extra DNS query, and there is a cap of 10 DNS lookups allowed for each email verification. 

To resolve this issue, SPF Flattening "flattens" the record by substituting the include mechanisms with the actual IP addresses or pertinent information from the SPF records of the referenced domains. This approach removes the requirement for additional DNS lookups and creates a more succinct SPF record.


Key Differences Between SPF Flattening and Regular SPF Records


DNS Lookup Efficiency

A key distinction between SPF Flattening and standard SPF records lies in the management of DNS lookups. Standard SPF records may generate several DNS queries because of the use of include mechanisms, potentially reaching the maximum limit of 10 lookups swiftly, particularly for domains utilizing many third-party email services. On the other hand, SPF Flattening removes the necessity for these additional lookups, resulting in a more streamlined and efficient method.


Record Size and Maintenance

Standard SPF records tend to be more flexible and simpler to manage. When an external service alters its IP address, you can easily adjust the include mechanism. In contrast, SPF Flattening requires you to manually revise the IP addresses each time a third-party service modifies its sending IPs. This implies that although SPF Flattening can minimize DNS lookups, it also poses potential maintenance difficulties, particularly if multiple services are involved.


SPF Record Length

Flattened SPF records are typically more extensive than standard SPF records because they list specific IP addresses for each service rather than employing include mechanisms. Although this approach provides a more detailed SPF record, it can complicate management. Additionally, a longer SPF record raises the risk of exceeding DNS record length limits, potentially hindering the proper publication of the record.



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Flexibility for Changing Providers

When you have a standard SPF record, transitioning to a different third-party email service is easy; all that’s required is modifying the include statement to reference the new service's SPF record. However, with SPF Flattening, you'll need to manually adjust the IP addresses in your SPF record each time you change email providers. This creates limitations on your ability to switch providers swiftly without risking problems with email delivery.


When to Use SPF Flattening vs. Regular SPF Records


  • Opt for SPF Flattening in the following situations:

    • When you've reached the 10-DNS lookup cap with your standard SPF configuration.

    • If you're looking to enhance the efficiency of SPF lookups and minimize reliance on external sources.

    • When your third-party vendors possess consistent IP addresses that seldom change.

  • Choose Regular SPF Records under these conditions:

    • If you have a limited number of external services and the 10-lookup limit is not an issue.

    • If you favor a more adaptable and simpler SPF record to manage.

    • If you often switch third-party providers, it is tedious to manually update flattened records. Get additional details here.