What is SPF Flattening?

Introduction

One of the biggest challenges organizations face is managing multiple legitimate email vendors and maintaining a valid SPF (Sender Policy Framework) record. Large enterprises with complex email infrastructures often hit the SPF DNS lookup limit of 10, which can lead to SPF failures, negatively affecting email deliverability and domain reputation.

SPF flattening is the process of resolving and replacing the include mechanisms in SPF records with their corresponding IP addresses, thereby reducing DNS lookups. However, manually flattening an SPF record is not scalable, as vendor IPs can change frequently.

This is where tools like Aquila | SPF Flattening come into play. Aquila not only flattens SPF records but also monitors changes made by third-party email vendors and automatically updates the DNS record — without requiring manual DNS login or edits.

What is SPF?

Sender Policy Framework (SPF) is an email authentication protocol designed to prevent email spoofing. It works by publishing a TXT record in the domain's DNS, which specifies the IP addresses and domains that are authorized to send emails on behalf of that domain.

Example SPF record for domain aquilai.io: v=spf1 include:spf.protection.outlook.com include:zoho.in include:sendgrid.net ip4:202.66.175.61 ip4:101.53.144.148 ~all

In this record, the include mechanisms authorize Microsoft (Outlook), Zoho, and SendGrid to send emails on behalf of aquilai.io. The ip4 mechanisms specify additional IP addresses that are also allowed to send emails.

This ensures that only the listed vendors and IPs are permitted to send emails using the domain. Any unauthorized sender will fail the SPF check, helping to protect against spoofing.

Understanding SPF Limitations

SPF comes with a key limitation — it allows a maximum of 10 DNS lookups. Each include, a, mx, or ptr mechanism generally counts toward this limit. If the total number of lookups exceeds 10, the SPF check will fail, potentially leading to email delivery issues, such as legitimate emails being rejected or flagged as spam.

SPF Mechanism	Counts as DNS Lookup?
include:	Yes
a	Yes
mx	Yes
ptr	Yes (and not recommended)
ip4: / ip6:	No

What is SPF Flattening?

SPF flattening is the process of resolving the domains specified in the include mechanisms of an SPF record to their actual IP addresses, and then listing those IPs directly within a single SPF string for the domain.

Before flattening:

v=spf1 include:vendor1.com include:vendor2.com ~all

After flattening:

v=spf1 ip4:192.0.2.1 ip4:192.0.2.2 ip4:198.51.100.1 ip4:198.51.100.2 ~all

The SPF Flattening Process

SPF flattening is a comprehensive and multi-step process. It begins by retrieving the SPF records of all domains referenced via include mechanisms. The system then identifies all DNS-based mechanisms that contribute to the SPF lookup count, resolves them to their corresponding IP addresses, and compiles these into a single list.

During this process, duplicate entries and deprecated mechanisms (such as ptr or overly nested includes) are removed to optimize the record for modern email infrastructure. The final result is a consolidated SPF record that contains only IP addresses—eliminating the need for additional DNS lookups and ensuring compliance with the SPF 10-lookup limit.

Flattening Process Steps:

1.       Retrieve all SPF records from include mechanisms

2.       Identify and resolve all DNS-based mechanisms

3.       Compile IP addresses into a single list

4.       Remove duplicate entries and deprecated mechanisms

5.       Create a consolidated SPF record with only IP addresses

6.       Monitor for changes in included domains' SPF records

7.       Automatically update the flattened record when needed

Benefits of Using Aquila | SPF Flattening

Implementing SPF flattening with Aquila offers a range of benefits for organizations looking to improve email deliverability and simplify SPF record management:

• Stay Within SPF Lookup Limits

  Eliminate the risk of SPF failures caused by exceeding the 10 DNS lookup limit.
  

• Improve Email Deliverability

  Reduce the chances of your legitimate emails being rejected or flagged as spam due to invalid SPF records.
  

• Automated Vendor IP Tracking

  Aquila automatically monitors and updates IPs from third-party vendors like Microsoft, Zoho, SendGrid, and others—no manual tracking or intervention needed.
  

• DNS-Free Updates

  No need to log in to your DNS provider to make SPF changes. Aquila syncs updates seamlessly on your behalf.
  

• Optimized and Clean SPF Records

  Duplicate, deprecated, or unsupported mechanisms are automatically removed, ensuring a clean and compliant SPF record.
  

• Enhanced Security and Control

  Maintain full visibility over which IPs are authorized to send on your behalf with detailed logs and real-time monitoring.
  

Best Practices for SPF Management — How Aquila Helps

Aquila I SPF Flattening is designed to align with industry best practices for dynamic SPF record management, ensuring your domain stays compliant, secure, and optimized for deliverability. Here’s how Aquila supports each key recommendation:

• Automated Monitoring & Updates

  Aquila I continuously monitors your SPF records and tracks IP changes from authorized vendors. It automatically updates your flattened SPF record to reflect those changes, ensuring real-time accuracy without manual intervention.
  

• Built-In Redundancy & Multi-Layered Support

  While SPF is critical, Aquila encourages and works alongside DKIM and DMARC to create a complete, multi-layered email authentication strategy—strengthening your domain’s security posture.
  

• Centralized Vendor Tracking

  Aquila I provides a consolidated view of all third-party services and sending IPs included in your SPF record. This helps teams keep clear documentation of their current email-sending infrastructure.
  

• Controlled Rollouts

  For organizations making a transition to SPF flattening, Aquila I supports phased rollouts and versioning, enabling smooth adoption with minimal risk of service disruption.
  

Conclusion

SPF flattening is a crucial technique for organizations dealing with complex email infrastructures and multiple vendors. By resolving include mechanisms to their IP addresses and consolidating them into a single SPF record, businesses can overcome the 10 DNS lookup limit while maintaining robust email authentication. Tools like Aquila | SPF Flattening make this process seamless and automated, ensuring that your SPF records stay current, compliant, and effective in protecting your domain's email reputation.