SPF flattening: Stay within DNS lookup limits
Sendmarc’s SPF flattening solution automatically resolves include mechanisms into direct IP addresses, keeping your business’s SPF record under the 10 DNS lookup limit. This prevents SPF failures, improves email deliverability, and ensures your domain stays protected from spoofing and misconfiguration.
Stay within limits. Deliver securely. Protect your brand.
What is SPF flattening?
Email is essential to business communication, but it’s also a primary target for cybercriminals. One of the most effective ways to protect a domain from spoofing and phishing is by implementing the Sender Policy Framework (SPF) protocol.
But as more marketing tools and third-party platforms are added, SPF records can become cluttered, sometimes exceeding technical limits and causing legitimate emails to be rejected or land in Spam.
An SPF flattening tool solves this by replacing every DNS lookup with its resolved IP addresses. This reduces the number of DNS lookups required for SPF checks , helping your organization stay within the strict 10-lookup limit.
Exceeding this limit leads to SPF failures, which impact deliverability and open the door to email-based threats. Flattening keeps your business’s SPF record clean, compliant, and optimized for secure delivery. Exceeding the limit also introduces security risks, as an overloaded SPF record is often ignored entirely by recipient servers, meaning the signal that this IP should not be sending on your domain’s behalf is ignored, too.
How SPF flattening works
Understanding SPF flattening
It helps to know how SPF records function to understand flattening. An SPF record is a DNS TXT entry that authorizes which email servers can send messages on behalf of your company’s domain by allowing the domain owner to specify exactly which IP addresses recipients can expect legitimate email to come from.
Each time your organization adds a platform like Google Workspace, Microsoft 365/Entra, CRMs, and email marketing tools, it uses include statements to authorize its email servers. Each of these statements triggers a DNS lookup.
Note: include isn’t the only mechanism available to domain owners, but it’s one of the most popular. Not all SPF mechanisms generate a lookup, but due to its wide use, includes consume the most lookups.
The problem? The SPF specification (RFC 7208) sets a strict 10-lookup limit. Go over it, and recipient servers might return a Permanent Error (PermError), ultimately rejecting or flagging your business’s emails.
SPF flattening addresses this issue by resolving each include into a direct IP list, publishing a simplified version of your company’s SPF record. This flattened record is faster, leaner, and far less likely to break.
Role of SPF flattening in DNS lookup limits
The SPF lookup limit isn’t a guideline; it’s a hard technical boundary. Even a perfectly correct SPF record will fail if it requires more than 10 DNS lookups. That can result in:
- Emails bouncing or ending up in Spam
- Delayed or lost business-critical messages
- Long-term damage to a domain’s reputation
- The possible delivery of emails from cybercriminals
SPF flattening is your organization’s safeguard against these issues. By reducing the number of DNS queries, it stays compliant with the limit, ensuring better deliverability, stronger protection, and improved trust in its emails.
Benefits of using SPF flattening
Improved email deliverability
A flattened SPF record helps your business’s legitimate emails pass authentication checks and reach the inbox instead of the Spam folder. By staying within the SPF lookup limit, your company avoids PermError failures that block important messages.
Enhanced domain security
Flattening your organization’s SPF record reduces the risk of domain spoofing and impersonation. When your business’s record is optimized and up to date, it’s significantly harder for attackers to send phishing emails that appear to come from it.
Compliance with email standards
SPF flattening keeps your company compliant with industry requirements, specifically RFC 7208 Section 4.6.4. It shows customers and partners that your organization takes email security seriously and follows best practices to protect its recipients.
SPF flattening features
Continuous monitoring & automated updates
Sendmarc automatically monitors your business’s SPF record to ensure the number of DNS lookups doesn’t exceed 10. We resolve lookups in real time, keeping your company’s SPF record valid, current, and fully optimized.
Compression optimization
Our flattening feature simplifies your organization’s SPF record by reducing nested include mechanisms, resolving all lookups, and publishing the most efficient version possible. This reduces errors, shortens the SPF record, and ensures full compliance.
Easy enablement
No need for manual DNS editing or deep technical knowledge. Sendmarc makes SPF flattening simple to activate – just a few clicks in our platform, and your organization’s record is fully optimized.
Sendmarc’s flattening solution is ideal for businesses of all sizes. Whether it be a small company or a global organization, our platform makes SPF management simple, secure, and effective.
Get started with Sendmarc’s solution today!
Why SPF flattening matters for modern businesses
Email authentication is essential for protecting brands, customers, and operations. As companies adopt more SaaS tools, cloud services, and third-party providers, SPF records naturally become more complex. Without proper management, this complexity can lead to technical failures and open the door to cyberthreats.
SPF flattening is the key to overcoming these challenges. By ensuring its SPF record stays within the lookup limit, your organization:
- Protects its domain from impersonation and phishing
- Ensures its emails reach their intended recipients
- Complies with industry regulations and standards
- Saves time and reduces the risk of manual errors
With Sendmarc’s automated SPF flattening solution, your business can take control of its email authentication, enhance deliverability, and protect its brand reputation.
Ready to optimize your SPF record and boost email security?