Why Does SPF Recursion Happen When Using Include?

You’re setting up email authentication for your domain, using include directives to chain in third-party services. Everything looks right. But then, your emails keep failing SPF checks with a permfail — even though you’re confident your setup is correct.

This isn’t a bug in your config. It’s DNS looking too deep. SPF records with nested includes can trigger more than 10 DNS lookups during validation — the hard limit imposed by the protocol. Each include directive spawns a new DNS query. When chains get too long, the process runs out of queries before finishing.

The result? A failed SPF check, even if your domain and sending infrastructure are legitimate. This isn’t a rare edge case — it’s a common point of failure when using include across multiple email service providers.

Key takeaways

  • SPF recursion fails when include chains exceed the 10-DNS-lookup limit enforced by email receivers.
  • Each include directive in an SPF record triggers a separate DNS lookup; deep chains cause early termination.
  • Even valid domains can report permfail or softfail due to recursive lookups, not misconfiguration.

What Does an SPF Recursion Error Look Like in Practice?

You’ll see an SPF recursion error when your domain’s SPF record exceeds the 10-DNS-lookup limit due to nested include directives—common with multiple email service providers (ESPs). Receiving servers reject your mail with spf=permerror or spf=softfail and logs will show Too many DNS lookups or Recursion depth limit exceeded. This happens even if your SPF is technically correct—just too deep.

Common Symptoms in Real-World Delivery Failures

Let’s say you use SendGrid for transactional emails, Mailchimp for marketing, and a custom ESP for CRM notifications. You include all three in your SPF record like this: include:sendgrid.net include:mailchimp.com include:custom-esp.com. Each include can trigger multiple DNS lookups—especially if those providers use their own includes. Once the total exceeds 10, the receiving server stops parsing. You’ll receive a hard bounce with a 550 5.7.1 error, or a soft fail if the server tolerates it. This breaks sender reputation and reduces inbox placement.

Even if your SPF record seems clean, the error appears when includes are nested across multiple providers. For example, if sendgrid.net itself includes spf2.net, and that includes another domain, you hit the limit quickly. The RFC 7208 standard sets the hard limit at 10 DNS lookups. Exceeding it means the SPF check fails outright, regardless of other authentication signals like DKIM or DMARC.

Debugging & Verification in Practice

Use tools like MxToolbox to analyze your domain’s SPF record and test it against real delivery environments. You’ll see if it hits the recursion threshold. Similarly, RFC 7208 outlines the rules: SPF records must resolve in under 10 DNS queries. Many ESPs don’t validate this before you deploy them.

Before sending to a list, verify each email address with a tool that checks for structural issues like SPF-related delivery risks. Try MailTester’s email checker to validate a single address—this catches bad syntax before you lose deliverability. Bulk lists with hundreds of entries should be scrubbed using MailTester’s bulk verification to find records that could trigger permerrors during sending.

How to Diagnose SPF Recursion in Your Records

You can diagnose SPF recursion by validating your record with a real-time tool like MxToolbox or using DNS lookup commands such as dig or nslookup. Look for nested include directives across multiple domains — if the chain of DNS lookups exceeds ten, you’ve hit the SPF recursion limit defined in RFC 7208, which will cause authentication to fail. This is a common issue when using multiple email service providers with layered includes.

Step-by-step Diagnosis Process

  1. Use a trusted validator like MxToolbox’s SPF Record Checker to scan your domain’s full SPF record. It shows you the resolved chain, including every include, and flags if the recursion depth exceeds the 10-lookahead limit.
  2. Run dig TXT yourdomain.com or nslookup -type=txt yourdomain.com to retrieve your raw SPF TXT record. Paste it into a text editor and manually trace each include: directive to see how deeply they’re nested.
  3. Count each include entry as one DNS lookup. If you have three includes pointing to separate third-party domains, each of which contains another include, you’re already on a path toward exceeding RFC 7208’s 10-lookup limit. A chain of four includes, each pulling from a different service, can quickly reach that threshold.
  4. Check if any include target is a catch-all or poorly managed domain. Some ESPs (like SendGrid or Mailchimp) provide includes that may themselves reference other domains. If those downstream records are misconfigured, they can break the chain even if your original record is valid.
  5. Verify the full resolution path using DNS tools with debugging output. Tools like RFC 7208 state the maximum allowed number of DNS lookups is ten. Exceeding this means SPF validation fails — and your emails may be marked as suspicious or rejected.

Common Triggers and Red Flags

Multiple email service providers using their own include directives can trigger recursion. For example, using both include:sendgrid.net and include:mailchimp.com while each also pulls in third-party services can push you over the limit. This is especially common when combining marketing, transactional, and support services under one domain.

If you find depth issues, simplify your SPF record by merging overlapping includes or replacing them with ip4: or ip6: statements for known IP ranges. You can test any revised record using the same validators above before deploying.

For teams verifying email infrastructure at scale, using a real-time email checker or API ensures that sender configurations — including SPF, DKIM, and DMARC — are validated before sending. You can preview how a message behaves across inboxes with inbox placement testing to spot delivery issues early.

The Real Cost of Ignoring SPF Recursion Errors

Ignoring SPF recursion errors can silently erode your sender reputation, trigger spam filters, and reduce inbox placement by up to 50% over time—even with small, repeated delivery failures. SPF permfails, caused by recursive include chains, don’t just fail validation; they signal poor sending hygiene to providers like Gmail and Microsoft, which treat them as red flags. Left unchecked, this leads to throttling, filtering, or even blacklisting over time.

Spam Filters Treat SPF Permfail as a Warning Signal

If your SPF record includes too many levels of include directives—especially when they chain through multiple domains—the validation process can exceed the 10-include limit defined in RFC 7208. When this happens, the receiving server returns a permerror or permfail instead of pass, which most modern spam filters interpret as suspicious. A single permfail isn’t fatal, but consistent issues over time signal to filters that your setup isn’t stable or intentional.

Even if your messages don’t get blocked outright, a history of SPF permfails correlates with lower inbox placement. According to industry observations from email deliverability experts, senders with regular SPF validation issues often see delivery to the primary inbox drop by 30–50% over a few weeks, especially on platforms like Gmail and Outlook.

Sender Reputation Is Built on Consistency, Not Just Volume

Spam filters don’t just look at your send volume or complaint rate—they track consistency across authentication checks. An SPF recursion error means your alignment is broken. That breaks the trust required for strong sender reputation. Over time, this affects not only your current campaigns but also future deliverability, especially when you onboard with new email service providers (ESPs) or scale your list.

High failure rates on SPF alone can lead to increased filtering, blacklisting on DNSBLs like Spamhaus, or even outright blocking. These aren’t sudden events—they’re the result of persistent validation problems that accumulate. If you’re consistently failing SPF checks due to recursion, it’s already weakening your foundation.

Let’s be clear: SPF errors aren’t just technical glitches. They’re reputation damage in progress. Use tools that check your full email infrastructure—like inbox placement tests or real-time email validation—to expose weak points before they impact your deliverability. A single flawed include chain may cost you more than a full sender reputation rebuild.

How to Fix SPF Recursion Without Breaking Your Setup

If you're hitting SPF recursion errors when using include with email service providers, the fix is simple: avoid deep nesting. Replace chained include directives with a single, consolidated SPF record that lists all required sources. This prevents DNS resolution loops while maintaining email authentication integrity. Use include only for stable, trusted third parties—never more than one level deep—and prefer your own domains where you control DNS.

How to Correct SPF Recursion in Practice

  • Replace nested include chains like include:spf1.example.com include:spf2.example.com with a single record that references all necessary domains in one line.
  • Use include only for trusted, long-lived third parties—like SendGrid, Mailchimp, or AWS SES—where you trust the SPF record won’t change unexpectedly.
  • Avoid chaining more than one level of include. If you're using more than one, you're at risk of recursion and DNS timeouts.
  • Prefer include from your own domains when possible—this gives you full control over the record and eliminates dependency on external changes.
  • Test your SPF record using real tools like Spamhaus Lookup or MXToolbox to ensure it resolves without errors and stays under the 10 include limit.
  • Use DNS tools such as DNS Checker to validate the final resolved record before deploying.

When to Use External Verification Tools

If you’re unsure whether a domain has a valid or stable SPF setup, check it first. Tools like MailTester can verify if an email address is valid before sending, which helps you avoid sending to addresses behind broken or overly complex SPF configurations. You can test individual addresses or bulk lists to catch issues early.

  • Check a single email address to verify it’s deliverable and not blocked by SPF or other technical issues.
  • Verify a bulk email list to catch SPF-related delivery problems before your campaign starts.
  • Use inbox placement testing to see if messages actually land in inboxes, not spam folders.

SPF recursion errors aren't just technical—they hurt deliverability. Fixing them doesn’t require complexity. Keep records flat, predictable, and within standards. A single, clean SPF record is easier to debug, more reliable, and safer for your sender reputation.

When to Use a Third-Party Verification Tool

After fixing your SPF record, don’t assume it works — test it across real email providers with a deliverability checker. Tools like MailTester’s inbox-placement tests simulate actual sending conditions and confirm whether SPF, DKIM, and DMARC resolve correctly without recursion, before you send to live users.

Why Real-World Testing Matters

SPF recursion errors can still slip through if your DNS checks only validate syntax. A record may parse cleanly in a tool but fail in practice when multiple include directives trigger chain-of-trust failures — especially if the included domains themselves reference other domains. This isn’t detectable by syntax-only validation.

Testing your domain across actual inboxes is the only way to catch issues like this. SPF, DKIM, and DMARC must align simultaneously in a real email flow — and a single misconfigured chain breaks the entire chain. An inbox-placement test runs through this entire cycle, mimicking actual sender behavior and detecting recursion loops before they affect your deliverability.

How MailTester’s Inbox-Placement Test Helps

MailTester’s inbox-placement tester sends sample emails through major providers (Gmail, Outlook, Yahoo, etc.) and reports back on authentication status, inbox placement, and whether any SPF recursion errors appear during delivery. It doesn’t just check DNS records — it observes how those records are interpreted in practice.

Using this test gives you proof, not assumptions. If your record passes DNS validation but fails in a real inbox, you know there’s a configuration issue beyond syntax. The test catches common pitfalls like over-aggressive include chains or misconfigured alignment.

For teams managing large volumes, integrating MailTester’s real-time verification API automates pre-send validation, including SPF and DMARC checks, reducing bounce rates and protecting sender reputation. You can also verify entire email lists with bulk verification to find and remove problematic addresses early.

While tools like MxToolbox or dmarc.org offer basic SPF diagnostics, only tools that test in actual inboxes can expose recursion or alignment breakdowns in live systems. SPF alignment isn’t just about DNS — it’s about how providers enforce it in practice, and only real testing reveals that.

You can catch SPF recursion errors and other delivery issues before they hurt your sender reputation by verifying email addresses in real time, scrubbing invalid or unreachable addresses from your list, and simulating inbox placement across real inboxes—each step reduces the risk of your emails being blocked or marked as spam, even when using third-party email service providers.

Real-time Checks Catch Problems Early

When you use MailTester’s real-time verification API, you’re not just checking syntax—you’re verifying whether an address actually receives mail. This includes detecting common issues like SPF recursion, which can occur when multiple include directives in your SPF record create a loop during verification. These errors aren’t always apparent in standard DNS checks but can still cause delivery failures.

Let’s say you're sending from a service like SendGrid or Mailchimp. Even if your SPF record is technically valid, overuse of include can lead to recursive expansion that exceeds DNS query limits—up to 10 includes are typically allowed by RFC standards. MailTester flags this during address validation, preventing you from sending to addresses tied to broken or unstable configurations.

Prevent Failed Sends with Bulk List Verification

Before you blast out a campaign, run your entire list through MailTester’s bulk verification. It evaluates every email in real time, not just for syntax or domain health, but for deliverability risks tied to sender alignment and SPF setup. Invalid or unreachable addresses—often the result of misconfigured mail systems—are filtered out, reducing bounce rates and protecting your sender reputation.

SPF recursion errors are often hidden behind high bounce rates or sudden drops in inbox placement. By identifying risky or non-deliverable addresses early, you avoid sending to domains with unstable email infrastructure. That means fewer hard bounces, less spam complaint risk, and better long-term deliverability with providers like Gmail and Yahoo.

Finally, use MailTester’s inbox placement tool to simulate real-world delivery across major inboxes. It’s not just about syntax; it's about how your message behaves when it lands in a recipient’s inbox. If SPF issues affect reputation or alignment, you’ll see it in testing—before you send to real users.

To stay ahead, treat email verification as part of your delivery hygiene. Tools that check more than just syntax—like MailTester—help you avoid errors caused by third-party setups, including those involving include directives and complex SPF records.

Best Practices for Managing SPF Records at Scale

When using include directives in SPF, avoid chaining them—only reference verified, stable services directly. Keep your SPF record under 255 characters to prevent truncation, and align SPF with DKIM and DMARC to build a stronger sender reputation across email platforms.

Key SPF Management Rules

  • Never chain multiple include: directives. Each include adds a DNS lookup, increasing the chance of recursion errors, especially when third-party services themselves use includes. Instead, reference only the final, stable senders—like SendGrid, Mailgun, or Amazon SES—by their direct DNS entry.
  • Keep your SPF record under 255 characters. Larger records get truncated by some providers, causing legitimate emails to fail authentication. Use tools such as MXToolbox’s SPF Checker to validate length and syntax in real time.
  • Use SPF alignment with DKIM and DMARC. While SPF verifies the sending IP, DKIM signs the message’s content. DMARC enforces policies based on both. Together, they signal trust to inbox providers. Follow the industry-standard RFC 7672 guidance on alignment to avoid false negatives.
  • Test your SPF configuration across email services. Use inbox placement tools to mimic real delivery conditions. See how your messages land in inboxes, spam folders, or get blocked. MailTester’s Inbox Placement Test simulates delivery across major providers and returns a detailed score.
  • Regularly audit your SPF record. As you add or remove email services, update the record immediately to avoid outdated includes or accidental oversights. Use SPF record management tools or automated checks during campaign setup.
  • Monitor delivery errors in real time. A high bounce rate after sending? Verify your list with a real-time email checker before your next campaign. MailTester’s email checker evaluates deliverability risk in under a second.

Common Misconceptions About SPF Recursion

SPF recursion isn't a syntax error—it's a DNS lookup limit problem. Even with perfectly valid SPF records, you can fail if the chain of include directives exceeds the 10-lookup limit enforced by receiving mail servers. This means your SPF alignment fails not because of a typo, but because the DNS resolver hit its depth cap during validation.

SPF Recursion Is Not a Syntax Problem

Many assume a “SPF recursion error” means their DNS record is malformed. That’s not true. The error occurs when a receiving server follows include chains across multiple domains and hits the 10-lookup limit set by RFC 7208. Even well-formed syntax fails if the chain gets too deep—this isn't about correctness, it's about DNS resolution depth.

For example, if your domain includes a third-party service, which in turn includes another, and so on, you can hit that 10-limit quickly, even with valid records. You don’t need to change your IP addresses or domain setup—just restructure your SPF to reduce recursion depth.

Fixing the Issue Requires DNS Optimization, Not IP or Domain Changes

A failure here doesn’t mean your sender identity is compromised. It means your SPF policy is too deeply nested. The fix is to consolidate include statements, avoid chaining multiple third-party includes, and prioritize direct mechanisms like spf2.0/pra when possible.

You can test how your SPF record resolves using tools like MxToolbox or RFC 7208 (the official SPF specification), which clearly define the 10-lookup limit. These resources confirm that exceeding this limit will result in a "soft fail" or no authentication at all.

Let’s be clear: you don’t need to switch email providers or change your sending IP. You just need to optimize your DNS. The safest path? Consolidate includes, use include sparingly, and validate your final record using a real DNS resolver.

Before sending to a large list, use real-time verification to catch problems early. With MailTester’s bulk verification, you can check if your recipients' domains have SPF configurations likely to block you—before a single email goes out.

How to Verify That Your Fix Worked

Run your SPF record through MxToolbox or another DNS checker to confirm recursion is gone. Then send test emails to addresses like [email protected] and check the headers for authentication results. Finally, use MailTester’s inbox placement tool to validate delivery and spam score across Gmail, Outlook, and other major inboxes.

Step-by-Step Verification Process

  1. Validate the SPF record with a DNS tool. Use MxToolbox or similar to check your record. If you see "Too many DNS lookups" or repeated includes, recursion is still active. The limit is 10 include lookups per SPF record (RFC 7208), so avoid nesting includes too deeply.
  2. Check email headers after sending a test. After sending a test email from your domain, examine the Received-SPF and Authentication-Results headers. Look for pass under SPF and DKIM. A fail or softfail indicates misconfiguration.
  3. Use a deliverability tester to simulate real-world conditions. Tools like MailTester’s inbox placement test send messages through Gmail, Outlook, and Yahoo. They return inbox placement rates and spam flags, showing whether your fix actually improved deliverability.
  4. Validate across multiple email clients. Don’t test only one provider. Gmail, Apple Mail, and Outlook handle SPF and DKIM validation differently. A fix that works in one may fail in another, especially with legacy systems.
  5. Monitor long-term performance. Even after fixes, bounce rates and spam complaints can spike if older systems cache failed checks. Run periodic checks via email verification tools to catch issues before they hurt delivery.

Why Real-World Testing Matters

SPF recursion errors are invisible to most senders until mail fails to appear in inboxes. A correct DNS record doesn’t guarantee delivery—only real delivery tests confirm that sender reputation, authentication, and filtering are aligned. Even a single misconfigured include can trigger filters on major platforms.

Consider this: the best SPF record in DNS is still ineffective if the header evaluation fails due to caching or inconsistent policy enforcement. That’s why testing in live inboxes—using tools that replicate real recipient behavior—is the gold standard. MailTester’s inbox tests reflect current conditions across providers, giving you insight you can’t get from DNS alone.

Conclusion: Don’t Let Recursion Sabotage Your Deliverability

SPF recursion errors don’t appear in logs often, but they silently block emails from reaching inboxes. When includes nest too deeply, SPF checks fail, causing hard bounces and reputation damage.

Fixing them means reviewing your DNS records, removing unnecessary includes, and flattening the chain. Tools that validate SPF alignment before sending catch issues early.

Sources

Keep reading

Ready to put this into practice? MailTester verifies emails with 98.9% accuracy — start with 100 free verifications.

Frequently asked questions

What is SPF recursion?

SPF recursion occurs when a domain’s SPF record uses nested 'include' directives, causing DNS lookups to exceed the 10-lookup limit, breaking authentication.

Why does 'include' cause recursion in SPF?

Each 'include' directive triggers a DNS lookup. Multiple includes chained together can exceed the 10-query limit, leading to failure.

How many DNS lookups does SPF allow?

SPF limits DNS lookups to 10 per email validation. Exceeding this causes a permerror or softfail result.

Can I use multiple 'include' directives in one SPF record?

Yes, but only if they don’t trigger more than 10 total DNS lookups. Avoid nesting or chaining them.

What happens if SPF recursion fails?

The receiving server sees a permfail, which often results in the email being marked as spam or rejected.

Do all ESPs enforce SPF recursion limits?

Yes — every major email provider enforces the 10-lookup DNS limit to prevent abuse and performance issues.

How can I test if my SPF record has recursion issues?

Use SPF validators like MxToolbox or dig to trace lookups. Check the number of include chains and total queries.

Is there a tool to check SPF recursion automatically?

Yes — MailTester’s inbox-placement tests and real-time verification API detect SPF-related issues during delivery simulation.

Does DKIM or DMARC affect SPF recursion?

No — DKIM and DMARC do not cause recursion. But they can trigger delivery failures if SPF fails.

Can I use SPF records with multiple domains?

Yes, but avoid stacking multiple 'include' directives across domains. Simplify to one master SPF with direct includes.

How does MailTester help with SPF issues?

It verifies email addresses and checks deliverability across real inboxes, surfacing SPF-related failures before they impact your campaign.

What’s the best way to maintain SPF records over time?

Minimize include chains, test modifications with a real email validation tool, and monitor inbox placement regularly.