Fix SPF Include Loop

Why Does an SPF Include Loop Break Email Deliverability?

You just sent a campaign to 50,000 subscribers—only to see 37% bounce. No spam traps. No invalid addresses. Just hard failures, silently eating your inbox placement. What if the problem isn’t the list, but your own DNS?

An SPF include loop happens when a domain’s SPF record references itself—directly or through a chain of includes that ultimately circle back. Mail servers detect this during DNS validation, and reject the message. It’s like trying to follow a map that says “turn left at the intersection, then go back to the start.” The system doesn’t work, and the message never ships.

Because SPF validation is mandatory for most major inboxes, a single loop can cause widespread bounces, degrade sender reputation, and trigger throttling—especially for large senders or those using third-party ESPs. Fixing this isn’t a minor tweak. It’s foundational.

Key takeaways

An SPF include loop occurs when a domain’s SPF record references itself, either directly or indirectly through a chain of includes.
Mail servers reject messages from domains with SPF loops because they cause infinite DNS lookup cycles during validation.
Even one loop breaks deliverability: it results in hard bounces, hurts sender reputation, and can trigger throttling by ESPs and inboxes.

How to Identify an SPF Include Loop Where Your Domain Includes Itself

You can identify an SPF include loop where your domain includes itself by checking your domain’s SPF record using DNS lookup tools. If you see include:yourdomain.com in your own SPF record, or if subdomains recursively point back to your main domain, the mechanism creates a loop. This breaks SPF validation and harms deliverability.

Check Your SPF Record with DNS Tools

Use a tool like MxToolbox or the terminal command dig txt yourdomain.com to retrieve your full SPF record. This shows the full, expanded version of the policy, including all include: directives.
Look directly for any include:yourdomain.com entry. If the SPF record for example.com includes include:example.com, that’s a loop. This is not valid by SPF specification.
Check for indirect recursion. For example, if example.com includes sub1.example.com, and that subdomain’s SPF record includes example.com, you have a circular dependency. This breaks SPF validation and can result in your emails being rejected.

Inspect for Recursion and Validation Errors

SPF records must be non-recursive. The SPF RFC explicitly limits the number of include: mechanisms to ten. A loop can cause a lookup to exceed this limit or result in a permanent error during validation.

Let’s say a sender checks your SPF. The validator resolves the first include:, follows it to another domain, resolves that record, and — if it includes the original domain again — hits a recursive path. This triggers a soft fail or permanent failure, depending on the receiver’s policy.

Use MailTester’s email checker to validate a single address before sending. It can show whether SPF is failing due to a loop. It also confirms whether your domain’s MX record and DNS setup are clean and compliant.

Fixing the loop is straightforward: remove self-referential include: entries. Replace them with direct mechanisms (like ip4: or include: to valid, non-recursive third-party domains). If you must include a subdomain, ensure its SPF does not point back to the parent domain.

You can’t rely on tools alone — you must review the expanded SPF output. An SPF record that includes itself is a guaranteed delivery problem. The fix isn’t complex, but it requires attention to detail.

Once you’ve cleaned the record, verify the result with a new DNS lookup. Always test with a real email delivery check — like MailTester’s inbox placement tester — to confirm the change resolved the issue across multiple provider inboxes.

What Happens When SPF Includes Itself: A Technical Breakdown

If your SPF record includes your own domain via an include: directive, you create a loop. Receiving mail servers resolve each include: by querying DNS. When the chain loops back to the original domain, the server hits recursive queries, which can time out, trigger cache poisoning protection, or fail entirely. This breaks SPF validation and can cause your emails to be rejected or marked as spam, even if your other authentication is solid.

How SPF Validation Works Under the Hood

SPF validation happens during the SMTP handshake, before any message data is sent. The receiving server checks your domain’s SPF record via DNS to verify it permits the sending IP.

Each include: directive triggers a new DNS lookup. If the included domain’s SPF record also includes your domain, you’ve begun a loop. The receiving server continues resolving until it either hits a timeout, exceeds the maximum number of DNS queries (typically 10), or detects a loop.

Standard DNS resolvers are designed to prevent infinite loops. They’ll either abort the query or flag the record as invalid if recursion exceeds limits. That means an SPF-in-self error isn’t just a configuration bug—it’s a real delivery risk.

Why This Causes Delivery Failures

SPF validation requires complete and correct evaluation. A loop interrupts that process. Receiving servers don’t wait forever; if resolution takes too long or fails due to recursion, the check fails by default.

According to RFC 7208 (the official SPF specification), SPF records must not cause infinite recursion. The RFC states that implementations should limit resolution to avoid performance issues. While it doesn’t define the exact number of queries, most servers enforce a cap—usually between 5 and 10.

Mail servers such as Gmail, Microsoft 365, and others implement these limits strictly. A loop means your SPF check fails, even if your DKIM and DMARC are correct. That can trigger delivery delays, rejections, or spam filtering.

Tools like MxToolbox and Spamhaus can help diagnose DNS-level issues but don’t verify loop logic directly. Manual review or automated SPF checkers are needed to catch self-inclusion.

Use MailTester’s bulk verification to check hundreds of domains for SPF record issues at scale—especially useful when cleaning up old or misconfigured email lists.

Common Scenarios That Cause Self-Referential SPF Includes

You create an SPF record that includes your own domain, like include:yourdomain.com, and accidentally cause a loop when that domain’s SPF record also includes back to itself. This breaks the 10-include limit and can trigger rejection by receivers. You might not notice until emails start bouncing or being marked as spam—especially in systems that validate SPF rigorously.

Copy-Paste Errors in DNS Configuration

Editing DNS records via copy-paste from templates or previous setups can introduce unintended self-references—especially if you don’t validate the result.
Check your SPF record after any edit. Use a real-time SPF validator like dmarcanalyzer.com to test for loops or malformed syntax.
Never assume a copied record is safe. Verify every include directive manually, especially if it references your own domain.

Templates That Auto-Insert Self-References

Some email platform templates or automated tools inject include:yourdomain.com without warning, especially when setting up sender policies for multiple subdomains.
Review any auto-generated SPF record before publishing. Tools like MailTester's email checker can validate individual addresses and reveal SPF-related issues early in the send process.
When in doubt, use a tool to test your entire SPF chain to ensure no domain points back to itself.

Shared SPF Policies Across Domains

When multiple domains share a single SPF policy (e.g., via a centralized email provider), and one domain’s record incorrectly includes another that points back to it, a loop forms.
This often happens in larger organizations managing dozens of domains with shared email infrastructure. The loop may go unnoticed until a major campaign fails.
To avoid this, audit all domains using the same SPF policy. Use a tool like MailTester’s bulk verification to test large lists and flag domains with broken or recursive records.

SPF validation is not optional for modern sending. A malformed record can silently block messages before they even reach an inbox.

Remember: SPF is designed to prevent spoofing, but misconfiguration creates its own problems. The key is testing—both your record syntax and its real-world behavior. Use real tools, not just theory. And if you're unsure, validate with a service that checks the full chain, not just a single header.

How to Fix SPF Include Loop: Step-by-Step Guide

If your domain’s SPF record includes itself, it creates a loop that breaks email authentication and harms deliverability. You fix it by editing your DNS TXT record to remove any include:yourdomain.com entries, replacing them with explicit mechanisms like a: or mx:, and ensuring all DNS lookups stay under 10. Use a real-time validator to confirm the fix works.

Step-by-step: Remove the Self-Reference

Log in to your domain’s DNS provider (like Cloudflare, GoDaddy, or AWS Route 53) and locate the SPF TXT record for your domain.
Review every include: directive in the record. If you see include:yourdomain.com, that’s the loop. Remove it entirely.
Replace the self-referenced include with a direct mechanism: use a: to authorize IPv4 addresses from your domain, or mx: to allow mail servers listed in your MX records. These do not trigger DNS lookups beyond your domain’s own records.
For third-party services (like SendGrid or Mailchimp), keep only include:provider.com — and only if necessary. Each of these adds a lookup, so keep the list lean.
Count all include: directives, a: (if using IP ranges), mx:, and ptr: (rarely used). Stay under 10 lookups total — more than that breaks SPF validation.

Verify the Fix Works

After editing, test your record with a free SPF validator. The SPF specification limits DNS lookups to 10. Exceeding this causes the record to fail silently, which harms sender reputation.

The 5 steps described in “Step-by-step: Remove the Self-Reference”, in order.

Double-check your DNS record is not split across multiple TXT records unless necessary — SPF only processes one TXT record per domain. Multiple records can cause ambiguity and validation failure.

Once you’re confident the record is correct, use your email service’s built-in authentication tools to test a sample message. If it passes, SPF is functional. If not, revisit the record for redundant or malformed entries.

Fixing a self-referencing SPF include is one of the most common, yet overlooked, issues blocking deliverability.

For teams sending at scale, catching these issues early saves time and prevents bounce rates from spiking. You can verify SPF validity alongside sender reputation using an inbox placement tester. Test real-world deliverability before launching campaigns.

Why You Should Never Use 'include:yourdomain.com' in SPF Records

You should never use include:yourdomain.com in SPF records because it creates a self-referential loop that DNS resolvers cannot resolve. Even if the record exists, strict DMARC-compliant receivers treat it as invalid, leading to delivery failures. This mistake is especially likely to trigger intermittent bounces with Gmail, Outlook, and Apple Mail due to their rigorous SPF validation.

The Self-Referential Loop Problem

If your SPF record includes include:yourdomain.com, DNS queries for that domain will fetch the same record again—creating an infinite loop. No resolver can resolve this path without a hard stop. Even if the record appears valid in a tool, it’s effectively broken from an email delivery standpoint.

SPF has a limit of 10 DNS lookups per evaluation. A loop consumes those quickly and results in a "permerror" or "temperror". Modern gateways like Google and Microsoft discard messages with permerror responses and may flag your sender reputation as unstable.

Why It’s Not Just a Technical Quirk

Even if you think the setup “works” locally, it’s not safe for production. The SPF specification (RFC 7208) explicitly prohibits includes that reference the same domain, as they introduce ambiguity and risk loops. Receivers that enforce strict SPF policy (which most do now) will reject mail or mark it as suspicious.

Intermittent failures are common—some messages pass if the resolver happens to cache the record, others fail. This inconsistency harms sender reputation over time, especially with gateways that use DMARC alignment and aggregate feedback.

Let’s say you manage a mailing list. You might see 10% of your emails bounce with "SPF permerror" on a given day. You’re not doing anything obviously wrong. But that’s exactly when the loop is silently doing damage.

Fixing SPF includes means reviewing all domains that appear in your SPF records and ensuring they point to external, trusted sources—never your own domain. Use tools like MxToolbox or your DNS provider’s record inspector to audit your SPF chain.

For email deliverability teams, verifying SPF structure is a key step before sending. With MailTester’s email checker, you can validate addresses and check for common SPF issues like loops before they hit your send queue.

Best Practices for SPF Record Configuration

Fixing an SPF include loop where your domain includes itself means removing self-references, keeping only one SPF record, limiting includes to trusted providers like SendGrid or Mailchimp, and never including your own domain. Use tools to validate syntax and resolve the include chain before publishing. This prevents authentication failures and ensures your emails reach inboxes.

How to Avoid Common SPF Pitfalls

Use only one SPF record per domain. Multiple records cause validation failures, even if one is technically correct.
Don’t include your own domain in an include: directive. Doing so creates a loop that breaks SPF verification and can lead to hard bounces.
Keep the number of include: directives low. The SPF specification allows only 10 DNS lookups; exceeding this results in a "permerror" and email rejection.
Only include third-party services you trust. Examples: include:_spf.sendgrid.net or include:simplelogin.com. Avoid adding internal or personal domains.
Use a dedicated SPF validation tool to check syntax and verify the resolution chain. This catches loops, invalid syntax, or overuse of includes before you publish.

Verify Before You Deploy

Even if your SPF record passes basic syntax checks, it can still fail in real-world conditions. Use a tool like Spamhaus Lookup or MXToolbox SPF Checker to analyze the full chain of includes and confirm no loops exist. These services are widely used in email operations and provide reliable feedback.

Once you’ve confirmed the record is valid and the chain resolves cleanly, publish it. Monitor delivery results and check for unexpected bounces or low inbox placement. If issues persist, test the same record with MailTester's inbox placement testing to see how your messages perform across major providers.

Remember: SPF misconfigurations aren’t just technical — they damage sender reputation. Fixing include loops early prevents long-term deliverability issues. It’s one check, but it matters.

You can catch SPF include loops and other sender policy flaws before they break your deliverability. MailTester’s real-time verification API checks email addresses against live email infrastructure, including SPF and DMARC compliance. It identifies problematic configurations like a domain including itself in its SPF record—common in misconfigured setups that result in delivery failures or spam filtering. This stops issues before they hit the inbox.

Real-Time Checks Prevent Real Failures

When you send bulk emails, every address should meet basic technical standards. MailTester’s API checks each email not just for syntax, but for actual sender policy alignment. SPF includes are evaluated for loops and recursion—like when a domain references its own SPF record in the include directive. Such setups are technically invalid and trigger rejection from DMARC-compliant receivers.

For example, if your domain spf.example.com has an include:spf.example.com, it creates an infinite loop. RFC 7208 explicitly warns against such patterns. MailTester detects this during validation and flags it as a policy error—giving you the chance to fix it before a campaign starts.

Inbox-Placement Testing Exposes Hidden Risks

Even if an email passes basic checks, it might still land in spam. MailTester’s inbox-placement test simulates delivery across major platforms—Gmail, Outlook, Apple Mail—using real infrastructure. These tests expose issues like policy mismatches, missing alignment, or unexpected DNS behavior that might stem from flawed SPF or DMARC records.

Let’s say your sender domain uses a third-party service with an outdated SPF record. If the include list references a domain that no longer exists or is self-referential, the receiving server may reject the email or mark it as suspicious. The inbox-tester catches these risks early by simulating real-world delivery conditions.

With bulk verification, you can clean your list at scale. Invalid, risky, or catch-all addresses get flagged. Misconfigured domains—those with policy loops or expired DKIM—show up clearly. You’re not just removing invalid addresses; you’re improving sender reputation and reducing bounce rates, which directly impacts deliverability.

Try it with our bulk verification tool or integrate the real-time API. If you’re checking individual addresses, use our email checker. All tools return accurate, detailed feedback—including sender policy issues—so you build reliable email systems from the ground up.

When You Should Validate SPF Configuration After Changes

Immediately after publishing a new SPF record, before sending bulk emails, and after integrating with a new email service provider, validate your SPF setup. Even a single misconfigured include can break your sending, lead to delivery failures, or worse—trigger spam filters. Use a real-time tool to catch issues like SPF include loops where a domain references itself before the record is live.

When to Test SPF After Changes

Immediately after publishing a new SPF record — DNS propagation can take time, and validation confirms the record is active and correctly parsed before you send.
Before launching any bulk email campaign — even a single invalid SPF check fails can cause entire batches to be rejected by receivers, especially if the sender’s reputation is already weak.
After integrating with a new ESP — tools like Mailchimp, Klaviyo, or SendGrid often add their own SPF records. If you don’t check, you may end up with an SPF include loop where your domain includes itself, violating industry standards.
When switching providers or migrating email infrastructure — ensure no old SPF records remain, and all new includes are valid and ordered correctly.

Why SPF Loops Matter

An SPF include loop where a domain tries to include itself (e.g., v=spf1 include:example.com include:example.com ~all) is invalid and causes a permanent failure. This isn’t just a technical glitch — it breaks DMARC alignment and can result in delivery failures or being flagged as spam. The SPF specification, as defined in RFC 7208, explicitly prohibits loops and recursive includes.

Let’s be clear: you can’t trust DNS alone. Many tools show a record as “published” but don’t validate the logic. A valid DNS record doesn’t mean it’s safe to send from. For example, Spamhaus notes that SPF failures are among the top reasons for email rejection at enterprise receiving gateways.

Use a tool like MailTester to test your SPF record across real receiving systems. The bulk verification feature checks both SPF and deliverability in one workflow — especially useful when you're cleaning and preparing a list after a change to your SPF policy.

What to Do If You're Still Seeing Delivery Failures After Fixing SPF

If you’ve fixed your SPF include loop but still see delivery failures, your problem may be deeper than a single DNS record. You need to test actual delivery paths across major inboxes, validate the full SPF chain including all included domains, and check if your sending domain or IP is blocked. These steps separate theory from real-world results.

Run inbox-placement tests with MailTester’s inbox tester. Even with correct SPF, your message might fail due to content filtering, reputation, or engagement signals. Use MailTester’s inbox placement tool to check how Gmail, Outlook, and Yahoo actually handle your message. You’ll see real-time outcomes—what ends up in the inbox, spam, or is rejected.
Trace the full SPF chain with a DNS analyzer. Tools like MxToolbox or DNSLint can resolve the full SPF record chain, showing if any included domain is misconfigured or missing policies. SPF checks are recursive; one weak link breaks the chain.
Check blocklist status in real time. A domain or IP on Spamhaus, SORBS, or similar lists will trigger immediate rejections. Use Spamhaus’ lookup service or SORBS’ tools to verify your domain and sending IP aren’t listed. Even after SPF fixes, a blocklist entry can kill deliverability.
Verify individual email addresses before sending. If your sending list includes invalid or catch-all addresses, they can harm sender reputation. Use MailTester’s email checker to screen addresses in real time. This catches errors early—before delivery even starts.
Assess your sending reputation. SPF is only one layer. If your domain or IP has a poor sending history—such as high bounce rates or low engagement—providers will still block you. Monitor reputation via third-party services like SenderScore or Microsoft’s SNDS.

Why These Steps Matter

Fixing SPF is necessary but not sufficient. A correct SPF record doesn’t guarantee inbox delivery. Gmail and Outlook evaluate dozens of signals beyond SPF, including content, sender history, and recipient engagement. What looks correct in DNS can still be blocked by real-world filters.

Spamhaus, for example, lists domains not only for spam but also for poor sending practices—something SPF alone won’t catch. A clean SPF doesn’t prevent you from being blacklisted due to low engagement or high complaint rates.

Always test across real inbox environments. A message with flawless DNS settings can still land in spam if the content triggers filters (like excessive links or risky keywords). Use Inbox Placement tests to simulate actual delivery and see how your messages are processed across platforms.

Keep your DNS records clean, monitor blocklists, and validate addresses before sending. That’s how you turn a technical fix into real deliverability.

Conclusion: Keep SPF Simple, Self-Reference-Free, and Verifiable

An SPF include loop where your domain includes itself is a preventable configuration flaw that harms deliverability by confusing receiving mail servers.

Fix it by removing self-referencing entries in your SPF record and validating that all included domains resolve correctly and are authorized.

Use real-world testing tools like MailTester to verify your SPF setup and ensure consistent inbox placement before sending to real users.

Sources

DMARC adoption among top domains surged 75% between 2023 and 2025 — from 27.2% to 47.7% — in the wake of Google and Yahoo's bulk-sender authentication requirements. — EasyDMARC 2025 DMARC Adoption Report (2025)
Since May 5, 2025, Microsoft Outlook requires SPF, DKIM, and DMARC from domains sending 5,000+ emails per day, rejecting non-compliant mail outright at the SMTP level with error 550 5.7.515. — Microsoft Outlook requirements (via MailOver bulk-sender requirements guide) (2025)

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Frequently asked questions

Can a domain include itself in its own SPF record?

No, it creates a loop that fails SPF validation. Email servers reject messages from domains with cyclical include references.

How many DNS lookups can an SPF record have?

SPF allows a maximum of 10 DNS lookups. Any record exceeding this limit is invalid and causes delivery failures.

What is the difference between SPF, DKIM, and DMARC?

SPF checks if the sending server is authorized. DKIM signs the email body. DMARC defines how to handle messages that fail SPF or DKIM.

How do I test if my SPF record is valid?

Use DNS tools like MxToolbox or dig to retrieve your TXT record, or use MailTester’s inbox-placement test to validate actual delivery.

Can SPF records be shared across multiple domains?

Yes—but only if the included domains are trusted and do not create loops. Sharing SPF records increases risk if one domain is compromised.

Why does my email bounce even after fixing SPF?

Bounces can stem from DKIM issues, DMARC policy, sender reputation, or blacklists. Test with end-to-end delivery tools like MailTester.

What is the risk of using 'include:yourdomain.com'?

It causes a self-referential loop. Even if the domain is valid, recipients may drop the message due to policy rejection.

Do all ESPs enforce SPF validation?

Yes, all major providers like Gmail, Outlook, and Apple do. A broken SPF record results in automatic rejection or spam marking.

Can MailTester detect SPF problems?

Yes, it tests sender policy compliance as part of inbox-placement and real-time verification, flagging loops and invalid configurations.

How often should I audit my SPF record?

At least quarterly, and immediately after adding new senders, migrating domains, or changing DNS settings.

Is it safe to use 'a:' in SPF?

Yes, 'a:' allows the domain’s A record IP to send emails. It’s reliable and doesn’t cause loops when used properly.

Can I have multiple SPF records?

No. Having multiple SPF records causes validation failure. Combine all rules into a single TXT record.