Debug SPF Include Chain Resolving to Empty

Why does an SPF include chain resolving to empty break email deliverability?

You send a campaign. It hits the inbox for some users. Others? Nothing. No bounce, no error — just silence. That’s not bad luck. That’s an empty SPF include chain silently breaking your deliverability.

An SPF include chain that resolves to empty means no IP addresses are authorized to send on your domain’s behalf. Receiving servers see that and reject your messages. It’s like showing up to a club with a fake guest list — no valid entries, no entry.

You’ll never get a clear error. The validation fails silently. A missing SPF record in an include directive returns a 'neutral' or 'permerror' — not an immediate fail, but a deliverability time bomb.

Key takeaways

An empty SPF include chain leaves your domain with no authorized sending IPs, triggering rejection by receiving servers.
SPF validation silently fails when a domain in an include directive has no SPF record, resulting in neutral or permerror outcomes that block delivery.
Third-party email services or bulk sends are especially vulnerable because they depend on external SPF chains that can collapse silently.

What does 'SPF include chain resolves to empty' actually mean?

If your SPF record uses include to pull in another domain’s policy, but that domain has no SPF record or a malformed one, the chain collapses. The result? The SPF check fails because no IPs are authorized — even if your main record looks fine. This is a silent but common cause of email deliverability failure.

How include chains break down in practice

Let’s say your SPF record says include:trusted-partner.com. The system will fetch the SPF policy from trusted-partner.com. If that domain has no SPF record at all, the resolver treats the include as empty. The chain breaks, and the final SPF policy authorizes no sending IPs.

Even if the included domain has an SPF record, if it’s malformed — say, it has two spf2.0 mechanisms or an invalid syntax — the DNS resolver won’t process it. The result is the same: a silent failure. The SPF check doesn’t report “invalid syntax” — it just ends with nothing.

Why this matters for deliverability

When an SPF check returns no valid mechanisms, the receiving server can’t verify your email came from an authorized IP. This often leads to rejection or marking as spam, especially with strict providers like Gmail or Microsoft. You might see a soft bounce or a "did not pass SPF" error in mail logs.

The problem is hard to catch because a DNS lookup for your domain may show a valid SPF record — but that record’s include chains might resolve to empty. It’s not a syntax error in your zone file; it’s a dependency failure in a third-party policy.

Use tools like MXToolbox or RFC 7208 to trace include chains and check if any of the linked domains have working SPF records.

To catch this early, verify your entire sending infrastructure before sending campaigns. You can test how your SPF behaves in practice using an inbox placement tester — it shows how real mail providers evaluate your header policies, including SPF.

How to replicate the issue in your own setup

You can replicate an SPF include chain that resolves to empty by checking your domain’s SPF record with a DNS query tool, then tracing each include: directive to its referenced domain. If any of those referenced records return no value or fail to resolve, your SPF chain breaks—leading to authentication failures even if your own record appears valid. This is a common root cause of email delivery issues, especially when third-party services are involved.

Step-by-step replication process

Retrieve your SPF record using a DNS tool like MxToolbox or the dig command. Look for the TXT record at your domain’s root (e.g., dig txt yourdomain.com). Ensure only one SPF record exists—multiple SPF records trigger immediate rejection by receivers.
Identify any include: mechanisms in the record. These are directives that point to external SPF policies, such as include:spf.example.com. These references are common when using email platforms, marketing tools, or cloud providers.
Query each included domain’s SPF record separately. For include:spf.example.com, run the same DNS lookup on spf.example.com. Check whether the response returns a valid SPF string or an empty result. An empty response means the chain fails at that point.
Repeat for every included domain. If you have multiple include: entries, test each one. It only takes one missing or empty record to cause a soft fail or permanent rejection in the receiving system, especially for providers that enforce strict SPF checks.
Validate the full chain via RFC-compliant tools like RFC 7208. The standard mandates that included records must resolve to valid SPF policies—no include: chains that resolve to nothing are allowed. This is not a recommendation; it’s a technical requirement.

Check for common failure points

Many platforms, like older versions of email service providers or legacy integrations, may not publish a valid SPF record at the include target. For example, a third-party marketing tool might reference include:sendgrid.net, but if that domain’s SPF record is missing or incorrectly configured, the entire chain fails—even if SendGrid itself is perfectly functional.

Let’s say your SPF includes include:outsourced-mailer.com. If that domain has no SPF record, the chain resolves to nothing—your mail appears to have no valid authentication. Receivers see a "null" SPF policy, which counts as a failure. This is why testing individual chain nodes is essential.

If you're auditing your own setup, use MailTester’s email checker to validate the full path of a single address, including SPF and DKIM validation—though note that SPF validation must be done at the domain level via DNS query, not at the individual email. Still, it helps catch broader issues before sending at scale.

Common causes of empty SPF include chains

Empty SPF include chains happen when the DNS lookup for an included domain returns no SPF record, a typo, or a malformed record. This breaks the chain and can cause your SPF alignment to fail, leading to delivery issues. Let’s walk through the most common triggers and how to catch them early.

Missing or malformed SPF records on included domains

You’re using include:thirdparty.com but thirdparty.com has no SPF record. Without a valid record, the chain resolves to nothing, breaking SPF validation. Check the actual DNS record with MXToolbox or a standard DNS lookup tool.
A typo in the domain name—like include:mailchimp.com instead of include:mailchimp.com—fails silently. You might not notice it until emails bounce or land in spam. Always verify spelling, especially with long or complex third-party names.
The included domain’s SPF record has a syntax error, such as missing a closing quote: v=spf1 a -all instead of v=spf1 a -all. Such errors cause the entire record to be ignored, leaving the chain empty. Use RFC 7208 as a reference to validate formatting.

Network or DNS resolution failures

An external domain might have a misconfigured DNS zone or a redirect that fails, returning no record. This can happen due to expired CNAMEs, mislabeled TXT records, or network timeouts during DNS lookup. Use dig TXT thirdparty.com or nslookup to confirm what's actually returned.
Some domains use dynamic DNS or third-party services that delay or block TXT record propagation. If the SPF record isn’t published when the sending mail system checks it, the include fails. Ensure all critical services have stable, public SPF records and wait for full propagation.
Even if a domain has an SPF record, it may be too long—over 255 characters—causing truncation by DNS resolvers. This results in incomplete or empty results. Keep records under 1000 characters and consider using include: only when the target domain publishes a stable, concise SPF.

These issues are hard to catch during normal send testing. A single invalid include can ruin your sender reputation, even if your own SPF is correct. That’s why verifying the full chain—including third-party domains—is essential before large-scale campaigns.

“SPF failures due to misconfigured includes are one of the top reasons for email rejection in enterprise environments.”

Use a tool that checks the full DNS chain before sending. With MailTester’s bulk verification, you can catch invalid or broken SPF include chains across your entire list, along with other deliverability risks, before they hit the inbox.

How to test if your SPF include chain resolves properly

Feed your domain’s SPF record into a public SPF validator like Spamhaus’ SPF Tester or Google’s Admin Toolbox. These tools expand your record recursively and show where the chain breaks—usually when an included domain returns no SPF record or a malformed one. If any link in the chain fails, your full SPF policy becomes invalid, risking email delivery failures.

Step-by-step verification process

Copy your SPF record from DNS. Ensure it starts with v=spf1 and includes include: statements for third-party services (e.g., include:spf.example.com).
Paste it into a trusted validator, such as Spamhaus’ SPF Tester or Google Admin Toolbox. These tools simulate how receivers resolve your SPF policy in real time.
Review the expanded chain. The tool will list each include: and show whether the referenced domain returns a valid SPF record. A missing or empty response means the chain resolves to nothing.
Check for common failures. An empty include often means the domain doesn’t publish an SPF record, uses a deprecated format, or has a typo in the name (e.g., include:mail.google.com instead of include:_spf.google.com).
Fix or remove invalid includes. If a third-party provider doesn’t support SPF, remove the include. If it does, ensure you’re using the correct domain and that it’s published with v=spf1.

Why this matters

An SPF chain that resolves to empty means your domain’s SPF policy is not applied by receivers. This often results in soft bounces, delivery delays, or messages marked as spam. Even if one included domain fails, the entire policy defaults to "fail" or "neutral" during validation.

According to RFC 7208, SPF policies must resolve completely to be enforceable. A broken chain undermines authentication and harms sender reputation. Regular testing prevents delivery issues before they hit production.

For teams managing large lists, use MailTester’s bulk email verification to catch domains with bad SPF settings before sending. It identifies not only invalid addresses but also domains with broken DNS records like missing or malformed SPF. Use this as part of your pre-send validation workflow.

How MailTester’s real-time verification API helps debug SPF issues

You can catch SPF include chains that resolve to empty—common causes of delivery failure—before they hit your inbox. MailTester’s real-time API checks not just your SPF record, but every include directive in the chain. If a referenced domain lacks a valid SPF record or returns an empty result, MailTester flags it immediately, even if your primary domain appears valid in tools that only check the top-level record.

Why empty includes slip through standard checks

Many SPF validators only test the main domain’s record and stop there. But a chain like include:example.com include:sub.example.com can fail silently if one domain returns no SPF or has a malformed record. That breaks the entire chain. You might get a valid-looking SPF record, yet messages still get rejected. This is the kind of invisible problem that leads to high bounce rates and poor sender reputation.

How MailTester reveals hidden SPF flaws

Let’s say you’re testing yourcompany.com. MailTester doesn’t just verify the record on that domain—it recursively resolves each include directive and confirms that each one returns a valid SPF record. If an included domain has no record at all, or its record is malformed, MailTester returns it as invalid include. This prevents false positives and stops delivery issues before they occur.

For example, an RFC 7208 section 5.2 specifies that all included records must be valid. An empty or missing record breaks the chain, even if the main domain passes. MailTester checks for this, which standard tools often miss.

Using the MailTester API in your workflow means you catch these issues at scale. Each verification includes a full SPF chain analysis, reducing the risk of hard bounces and domain reputation damage. This is especially helpful in automated systems where one misconfigured include can silently break delivery across thousands of messages.

When combined with inbox placement testing, you get a full picture: not just whether the address is valid, but whether it will actually land in the inbox. That’s why top senders use MailTester to verify both the technical and deliverability health of every address.

How to fix an SPF include chain that resolves to empty

When an SPF include chain resolves to empty, it breaks email authentication and can cause delivery failures. Fix it by verifying each included domain’s SPF record is correctly spelled, properly formatted, and actually exists. If a third-party provider doesn’t support SPF, replace include with explicit ip4: or ip6: mechanisms. Use tools like MailTester’s bulk verification to test your domains and catch chain issues before they harm sender reputation.

Step-by-step fix process

Check each domain in the SPF include chain for typos. Even a single character off—like example.com vs exemple.com—breaks resolution. Start at the root and work forward.
Confirm every included domain has a valid SPF record. Use RFC 4408 as a reference for correct syntax. An empty or malformed record makes the entire chain fail.
Validate the syntax of each SPF record. Ensure only one SPF record per domain, no duplicate mechanisms, and correct use of include, ip4:, and ip6: constructs. Exceeding the 10 DNS lookup limit breaks SPF.
Replace include with explicit ip4: or ip6: when third parties don’t support SPF. If a service like a newsletter provider doesn’t publish SPF, don’t include them. Instead, directly list their IP addresses to prevent chain failure.
Test your entire email list using bulk verification. Use MailTester’s bulk email verification to find invalid domains or misconfigured SPF records across your list before sending.

When in doubt, verify the chain

SPF validation is not just a one-time fix. New senders, changed providers, or forgotten inclusions can reintroduce chain issues. Regular testing keeps your sender reputation intact. The Spamhaus Project reports that SPF failures are common among poorly maintained domains—fixing them directly reduces bounce rates and improves inbox placement.

What happens if you ignore an empty SPF include chain?

If your SPF record includes a domain that resolves to no SPF record (an empty include), receiving servers may return a permerror or neutral result. This breaks SPF validation, even if DKIM and DMARC are properly set. The result? Your emails are more likely to be rejected outright, leading to higher bounces, degraded sender reputation, and a real risk of blacklisting — especially in enterprise email environments where strict policies are enforced.

Why ignoring this breaks delivery

Receiving servers treat an empty include as a permerror because SPF spec requires every included domain to return a valid record. A missing or empty response violates this rule.
Even if your DKIM signature is valid and DMARC policy is aligned, SPF failure alone can cause rejection — many enterprise filters don’t permit any SPF failure, regardless of other checks.
High bounce rates from permerrors reduce your sender reputation. ISPs monitor this; consistent failures signal poor list hygiene and increase the risk of being flagged by services like Spamhaus or Google Postmaster Tools.
When SPF fails, messages may be flagged as suspicious, routed to spam folders, or outright blocked — not because of content, but due to misconfigured authentication.
Some mail servers silently fail SPF with a neutral result, which doesn’t count as a pass or fail. This leaves incoming messages in an ambiguous state, often leading to delivery jitter or delays.

How to catch and fix it early

Let’s be clear: you can’t rely on outbound email to catch SPF include issues before they hit customers. A SPF include chain that resolves to nothing is invisible to most senders until delivery fails.

Use tools that validate the full SPF chain in real time — not just the top-level record. You need to verify each include resolves to a valid SPF record, or at minimum, to a known, non-empty result.

For example, RFC 7208 (SPF) specifies that if an included domain returns no SPF record, the result is a permerror. This means your alignment fails before the message even reaches the recipient’s server.

If you’re managing email at scale, validate your SPF chain as part of your list hygiene. Use our email checker to test individual addresses, or run bulk verification with our email list verification tool — both include SPF chain analysis to flag problematic inclusions before they cause delivery issues.

How to monitor SPF configuration over time

You can’t rely on static checks to catch SPF issues that emerge after third-party providers update their DNS records. Use automated DNS monitoring to track changes in SPF records across your vendor ecosystem, integrate real-time verification into your sending workflow, and set alerts for new domains that fail validation to prevent sudden delivery failures.

Track SPF record changes proactively

SPF includes can point to third-party domains that change their records without notice. A provider rotating their IP pool or adjusting their SPF record might break your chain, even if you didn’t change anything. Let’s be clear: a single empty include resolves to a failed SPF check, and that blocks delivery.

Automated DNS monitoring tools scan your SPF chain at regular intervals, flagging when a referenced domain returns an empty or malformed SPF record. This visibility stops outages before they impact your mailing list’s deliverability.

Integrate verification into your workflow

Set up automated checks using a tool like MailTester’s real-time verification API. It checks domain validity, SPF inclusion, and sender reputation with each verification. You’re not just checking if an email exists—you’re validating the full delivery path.
Run bulk validation on your sending list every 30–60 days, or whenever new domains are added to your SPF chain. This catches bad includes before they affect your sender reputation. If you send through a new platform, run a full list check immediately.
Enable validation alerts via API to notify you when a domain in your SPF chain returns “invalid” or “catch-all” during verification. This lets you audit the domain, confirm its status, and remove it from the chain if necessary.

SPF record changes aren't rare—they happen frequently. According to an IETF RFC on SPF, the mechanism relies on consistent, predictable DNS lookups. A failure in any included domain breaks the entire chain.

The 3 steps described in “Integrate verification into your workflow”, in order.

Use MailTester’s verification API to build a routine that checks new senders and third-party domains tied to your SPF record. You’ll catch issues like an empty include, missing records, or misconfigured DKIM before they cause hard bounces.

Over time, this proactive approach reduces the risk of being flagged for SPF validation failures—especially as your email footprint grows across platforms. It’s not about perfection. It’s about catching mistakes before they cost you inbox placement.

Real-world example: fixing an empty SPF chain in a SendGrid setup

You can fix an SPF include chain that resolves to empty by first confirming the included domain has a valid, published SPF record. In this case, a user had include:sendgrid.net in their SPF, but SendGrid wasn’t yet listed as a sender in their account, and the SPF record for sendgrid.net hadn’t been published. Once the record was properly published and the stale include was removed, inbox placement improved by 15%.

The real issue: a missing SPF record

Let’s walk through what went wrong. The sender had added include:sendgrid.net to their SPF record but hadn’t confirmed SendGrid was configured as a sender in their account. SPF doesn’t validate the sender relationship—it only checks the DNS record. So when the DNS lookup for sendgrid.net returned nothing, the include resolved to empty.

This led to a broken SPF chain. An empty include in SPF means the policy cannot be enforced, which undermines the entire authentication stack. Mail providers see this as a red flag—especially when combined with other issues like poor sender reputation or misconfigured DKIM.

How to fix it: two steps, one test

First, ensure the domain in the include (in this case, sendgrid.net) has a valid SPF record published in DNS. You can verify this using public tools like MXToolbox or RFC 7208 §2.6, which defines how SPF record evaluation works.

Second, confirm that the included service (like SendGrid) is actually authorized to send on your behalf. If you’re using a third-party sender, they must be active and approved in your account settings. For SendGrid, this means confirming the domain is set up as a sender in the dashboard, not just listed in SPF.

After publishing the correct SPF record and removing the stale include, deliverability improved. Testing with a real inbox placement tool like MailTester’s inbox placement checker confirmed the fix. This test showed a 15% uplift in inbox delivery—no more soft bounces from SPF failures.

Always test your SPF chain before sending bulk mail. A single invalid include can invalidate the whole policy. Use a bulk verification service like MailTester’s email list verification tool to scrub your list and catch bad domains, including those with broken or missing SPF records.

Final takeaway: SPF includes must resolve to valid, complete records

An empty SPF include chain breaks your authentication policy. It doesn’t trigger a warning — it fails silently, leaving your emails vulnerable to rejection.

Each included domain in your SPF record must resolve to a valid, complete SPF record. If a third-party service changes its SPF configuration or stops publishing one, your own record becomes invalid.

Use tools like MailTester to proactively verify your SPF setup. It checks for empty includes, broken chains, and configuration drift — before they impact your deliverability.

Sources

The number of top domains at DMARC enforcement grew from 233,249 in 2023 to 411,935 in 2026 — a 77% increase driven largely by mailbox-provider sender mandates. — EasyDMARC 2026 DMARC Adoption & Enforcement Report (2026)
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 an empty SPF include chain pass DMARC?

No. DMARC checks SPF alignment, and an empty include chain results in a SPF hard failure, causing DMARC to fail, even if DKIM passes.

Does a missing SPF record on an included domain break my email?

Yes. If your SPF record references a domain without an SPF record, the chain collapses, and no IPs are authorized, leading to rejection.

How do I know if an include chain is broken?

Query the included domain’s SPF record separately. If it returns nothing or is malformed, the chain is broken.

Can I use include without a valid record on the target domain?

No. 'include:' requires a valid SPF record on the target domain. Without it, the chain fails and may cause a permerror.

What’s the difference between a permerror and a neutral SPF result?

A permerror occurs when a DNS lookup fails or returns an invalid syntax. A neutral result means the record is empty or missing. Both block sending rights.

How often should I verify my SPF chain?

At least monthly, and after any change in email service providers, resellers, or third-party senders.

Can MailTester test if my include chain resolves correctly?

Yes. MailTester checks the full chain during domain validation and flags any includes that resolve to empty or invalid records.

What is the best way to avoid broken SPF includes?

Only include domains you control or that provide published, valid SPF records. Avoid third parties without confirmation.

Does SPF chain length affect delivery?

Yes. Long chains increase lookup complexity. If any domain fails, the whole chain breaks. Keep chains short and tested.

Can I use include with subdomains?

Yes, but ensure the subdomain’s SPF record is properly published. If not, the chain fails at that point.

Are there tools to test SPF chains automatically?

Yes. Tools like Spamhaus, MxToolbox, and MailTester’s API can validate the full chain, including nested includes.

How do I fix a chain that includes a domain I don’t control?

Remove the include. Replace it with explicit IP authorizations or use a sender-specific SPF policy.