Every time you send an email, the receiving mail server asks one fundamental question: "Are you who you say you are?"
Because the original design of the internet didn't have built-in identity verification, it became easy for bad actors to "spoof" email addresses—sending a message that looks like it came from your domain when it didn't.
SPF (Sender Policy Framework) was created to solve this. It is a simple DNS record that acts like an authorized guest list. It tells the world exactly which IP addresses and services (like Google Workspace, Microsoft 365, or SendGrid) are allowed to send mail on your behalf.
A typical SPF record looks something like this:
v=spf1 include:_spf.google.com include:sendgrid.net ~all
While it looks simple, the mechanisms inside (like include, a, mx, ptr, exists, and redirect) are actually instructions for the receiving server to go out and look up more information.
For example, when a server sees include:_spf.google.com, it doesn't just see a name; it has to pause, perform a DNS query for that domain, and check the list of IPs inside that record. This process is known as a DNS Lookup.
To ensure that email delivery is fast and to prevent "denial of service" attacks (where a malicious record could force a server into an infinite loop of queries), the official internet standards (RFC 7208) impose a strict limit: An SPF check must not require more than 10 DNS lookups.
As businesses grow and add more tools—CRMs, marketing platforms, support desks, and security services—it becomes incredibly easy to exceed this limit.
If your SPF record triggers 11 or more lookups, the receiving server will return an SPF PermError. To the recipient, your email looks "broken." Often, these emails are instantly flagged as spam or rejected entirely, even if you are a perfectly legitimate sender.
SPF Flattening is the process of taking a complex, nested SPF record and "compressing" it into its final, simplest form.
Instead of your DNS record saying "Go ask Google, then ask SendGrid, then ask our web host," a flattened record says: "Here is the list of every authorized IP address."
A flattener tool goes through every include and mechanism in your record, following the trail until it reaches the final IP addresses.
It removes any overlapping or redundant IP ranges to keep the list as short as possible.
The flattener generates a list of raw ip4 and ip6 addresses. Because these mechanisms do not require a DNS lookup, the recipient server can verify your identity instantly.
By flattening your record, you reduce your lookup count from 10+ down to 1, ensuring 100% deliverability while staying within the strict limits of global email standards.
It might be tempting to resolve your SPF record once, copy the IP addresses, and paste them into your DNS. However, there is a major catch: The internet is dynamic.
Email service providers (like Google, Microsoft, or your CRM) frequently update their infrastructure. They might add new IP ranges for a new data center or retire old ones for security reasons. When they do, they update their own SPF records.
Effective SPF flattening must be a continuous, automated process.
A reliable flattener monitors your providers and updates records automatically as changes occur. This ensures your list stays current without you ever lifting a finger.
This is exactly where SPF.Zone comes in. We take the complexity of SPF management off your plate with a fully automated, enterprise-grade flattening process.
We instantly compress your complex records into a lean list of authorized IPs.
Our system continuously monitors your providers. If Google, Microsoft, or any other service updates their IPs, your record is updated automatically.
Stay under the 10-lookup limit forever and ensure your emails always reach the inbox.
SPF.Zone turns a complex, fragile part of your infrastructure into a reliable, "set it and forget it" service.
Flatten Your Records Now