Why Does Your SPF Record Break When You Add Multiple Include Statements?

You've added a few include statements to your SPF record to cover third-party services—SendGrid, Mailchimp, a CRM—and suddenly your emails start bouncing. You didn’t change anything else. Why? SPF records aren’t just simple lists. They’re governed by technical limits. Each DNS TXT record can hold only 255 characters. When you use multiple include statements, their combined length grows quickly. Add a few too many, and the total record exceeds DNS capacity—causing a validation failure, even if the logic is otherwise sound. You might assume SPF validation is straightforward. But it’s not: every include statement adds load, and even one malformed or unreachable include can trigger a fail, especially if your record uses a strict policy like 'all' without a fallback.

Key takeaways

  • SPF records are limited to 255 characters per DNS TXT record, and multiple include statements quickly accumulate beyond that limit.
  • A single malformed or unreachable 'include' directive can cause SPF validation failure if the record lacks a forgiving mechanism like 'all' or 'fail'.
  • SPF record validation tools should inspect the full, resolved record—including all includes—to catch size and syntax issues before they break email delivery.

How Does SPF Validation Fail with Multiple Include Statements?

SPF validation fails with multiple include statements when any included domain is unreachable, returns a malformed DNS record, or causes the total mechanism count to exceed the 10-limit imposed by RFC 7208. Even one invalid include breaks the entire chain, and some providers treat any unresolved element as a hard fail, regardless of how many others are valid.

SPF records rely entirely on DNS lookups. Each include: directive fetches another SPF record from a remote domain. If that domain is unreachable, misconfigured, or returns a malformed response, the parser stops and marks the full SPF record as invalid. This cascade failure happens even if 9 out of 10 includes are functional.

Mail providers like Gmail and Microsoft Outlook follow RFC 7208, which explicitly defines a mechanism failure as a reason to reject email if resolution fails. This means a single broken include can cause your entire domain’s SPF evaluation to fail, even if 90% of the chain is intact.

When Nested Includes Break the Mechanism Limit

Every include:, ip4:, ip6:, and all counts toward the 10-mechanism limit. If you nest includes deeply—like include:example.com which itself includes another domain—they accumulate rapidly. A chain of three includes, each pointing to another valid SPF, may easily hit or exceed the limit.

When this happens, the DNS parser rejects the entire record. The outcome? A softfail or fail in SPF checks, which harms sender reputation and increases the risk of email being blocked or routed to spam.

Tools like MailTester help you catch these issues before they impact deliverability. With an SPF record validator that checks each include recursively, you can find broken chains, oversized mechanisms, and resolution failures before they hit production.

Let’s be clear: SPF isn’t just about writing a correct record—it’s about ensuring every linked domain is stable, properly published, and within technical limits. One weak link can invalidate everything.

For the full picture, check how your domain’s SPF performs in real email environments. Use our inbox placement tester to simulate delivery across major providers and identify SPF-related delivery failures.

What's the Right Way to Validate an SPF Record with Multiple Includes?

You need a real SPF validator that checks both syntax and DNS resolution across every included domain. Don’t rely on basic tools that only parse the text—true validation requires querying the actual DNS for each include statement. Keep each include result under 255 characters when combined, and avoid nesting more than two levels deep to prevent resolution timeouts or failures.

Use a Validator That Resolves DNS, Not Just Parses Syntax

Many tools check the structure of an SPF record but don’t actually resolve the DNS for included domains. Let’s be clear: an include statement is only valid if its target domain’s SPF record is reachable and parses without error. Without real DNS resolution, you’re blind to issues like misconfigured DNS, failed lookups, or malformed records in the included domains.

Tools like the one at RFC 7208 (SPF specification) enforce this requirement—any implementation must attempt DNS resolution for all include statements. A real validator must do the same.

Follow the Limits—and Check for Hidden Failures

Each include can add significant length. When combined, the final SPF record must stay under 255 characters. Exceeding that limit causes the record to be rejected by the receiving server, leading to hard bounces or spam filtering.

Nesting more than two levels deep increases the risk of DNS timeout. Each additional layer means another DNS query. If any upstream record fails to resolve or takes too long, the entire verification collapses. You’re not just breaking a rule—you're creating a point of failure that can affect every outbound email.

  • Use a real-time SPF validation tool that performs DNS queries for every include statement.
  • Check the final combined length of your SPF record—no more than 255 characters.
  • Limit nesting to two levels. Avoid include inside a domain that itself includes another.
  • Verify each included domain’s SPF record is valid and accessible via DNS.
  • Use a bulk email verification service like MailTester’s bulk verification to test SPF-compliant domains at scale.
  • Test SPF records with real-time tools that simulate how receiving servers evaluate them, not just static text rules.

Let’s be honest: SPF isn’t about perfection. It’s about consistency and reliability. A single misbehaving include can break your entire email program. The right tool doesn’t just scan syntax—it validates behavior under real conditions.

SPF Record Validation Process: Step by Step

You paste your full SPF record into a tool like MailTester’s SPF checker, and it walks through every include statement, recursively resolving each one’s DNS TXT record. It checks for syntax errors, missing or malformed includes, and total size—flagging any that exceed the 255-character limit per DNS query or the 10-include limit. It then returns a clear status: valid, invalid, or blocked by size or DNS failure.

  1. Paste your complete SPF record. Start with your full TXT record, including all include statements, like v=spf1 include:_spf.example.com include:sendgrid.net ~all. This is the foundation of what gets validated.
  2. The tool parses every include directive. It breaks down your record and identifies each include to resolve its target domain. For example, include:sendgrid.net means fetching the SPF record from that domain.
  3. It recursively resolves each included domain’s SPF TXT record. The tool doesn’t stop at the first include—it follows each one, checking the DNS response for correct syntax, presence, and structure. This happens up to the maximum allowed depth (typically 10 includes).
  4. Each include is flagged if malformed, empty, or exceeds size. If a referenced domain returns no TXT record, an empty response, or a syntax error (like an improper v=spf1 tag), the tool marks it as invalid. Many providers, like Amazon SES or SendGrid, define their own SPF records—ensuring those are properly formatted is critical.
  5. Total size of the final resolved record is calculated. SPF records are limited to 255 characters per DNS query. If the combined result of all includes exceeds this, the record will fail silently in delivery, even if syntactically correct. Tools like RFC 7208 specify these limits.
  6. Status is returned: valid, invalid, or failed. The output clearly says whether your record is acceptable to email receivers. If the record is oversized, the tool identifies which include caused the overflow, helping you optimize.

Why This Matters for Deliverability

Every mail server checks SPF records before accepting emails. A misconfigured include can break the entire chain—even if one include fails, your SPF record can be rejected. This leads to higher bounce rates, poor inbox placement, and damaged sender reputation. Testing early with a tool like MailTester’s bulk verification or the SPF checker API catches these issues before they affect your campaigns.

What to Do With the Results

If the tool finds a failing include, investigate that domain’s SPF record. Some services allow only one include per account. If the total size is over 255 characters, consider using a redirect (like include:spf.example.com → include:_spf.example.com), or consolidate providers where possible. Always test after changes. For ongoing verification across lists, use MailTester’s integrations with Mailchimp, Klaviyo, or SendGrid.

SPF Record Size and Limitations by Design

You can’t exceed 10 DNS lookups in an SPF record, even if your syntax is perfect. Each include statement counts as one lookup, so stacking multiple includes quickly hits the limit set by RFC 7208. If you go over, SPF fails silently—your emails may be rejected without a clear reason. Also, the final resolved SPF string must stay under 255 characters per DNS TXT record.

Why the 10-lookup limit exists

SPF’s 10-lookup rule is built into RFC 7208 to prevent DNS abuse and slow lookups. Every include triggers a separate DNS query. If you include too many domains—especially third-party services with their own includes—you risk hitting that cap. Once exceeded, SPF evaluation stops and fails, even if the rest of the record is valid.

Let’s say you include three major platforms, each with two levels of includes. That’s already 6 lookups. Add a few more trusted IPs or vendors, and you’re close to the limit. It’s easy to exceed 10 without realizing it, especially when one include points to another that chains further.

Length matters: the 255-character rule

Even if you stay under 10 lookups, your SPF record must fit within 255 characters per DNS TXT record. When includes resolve, the final string can get long fast—especially with long domain names or extra syntax.

For example, a clean SPF like v=spf1 include:_spf.google.com include:servers.mcsv.net -all resolves to over 300 characters once expanded. That breaks the limit and triggers a syntax error, even though the format looks correct. DNS only allows one record per 255 characters, so you must split or simplify.

If you’re managing SPF across multiple domains or using complex infrastructure, this constraint makes manual validation risky. You might think your record is fine, but a single unresolved include can push you over the edge.

That’s where tools like MailTester's bulk verification help—not just for email lists, but for testing how your domain’s SPF holds up in real-world conditions. It checks not just syntax, but whether the full chain of includes resolves without hitting the lookup or length limits.

For developers or admins, MailTester’s real-time API lets you validate SPF records programmatically during setup or deployment. It’s not a substitute for DNS checks—but it surfaces problems before you send mail.

Ultimately, you can’t override RFC 7208’s limits. But you can design around them: avoid deep nesting, consolidate includes when possible, and keep your record clean and compact. Use tools that surface these issues early—before they break deliverability.

How MailTester’s SPF Validator Handles Multiple Include Statements

You can validate SPF records with multiple include statements using MailTester’s tool, which resolves each include in sequence, checks DNS TXT records, warns about lookup limits, and flags issues like malformed domains or size overruns—all in real time. It doesn’t just tell you if your SPF is valid; it shows you exactly where it fails.

What the Tool Checks, Step by Step

  • It resolves each include directive in order, verifying that each referenced domain has a valid DNS TXT record.
  • It counts DNS lookups in real time and alerts you if the total is approaching the 10-lookup limit defined in RFC 7208.
  • It calculates the final size of the SPF string after all includes are resolved and warns if it exceeds 255 characters, which can break SPF validation.
  • It flags empty, unreachable, or malformed include domains—like those with missing DNS records or incorrect syntax.
  • It returns a clear verdict: Valid, Invalid, Too Many Includes, Exceeds Size Limit, or DNS Resolution Failed.

Why This Matters in Practice

Many organizations accidentally exceed the 10-lookup limit by stacking multiple third-party services (like marketing platforms and email gateways) in their SPF record. This causes SPF soft failures and can hurt deliverability—even if the syntax looks correct. RFC 7208 sets the limit to prevent DNS overload and ensure reliable validation.

MailTester’s SPF validator goes beyond basic syntax checks. It simulates how email receivers process your record—exactly as they would—catching issues that tools with minimal DNS probing might miss.

Need to audit a large list? Use MailTester’s bulk verification to validate SPF across thousands of domains in minutes.

Want to add this to your workflow? The real-time verification API supports SPF validation as part of broader email hygiene checks.

What Happens When SPF Fails Due to Multiple Includes?

If your SPF record contains too many include statements—more than 10, as defined by RFC 7208—you risk exceeding the DNS lookup limit. When this happens, mail servers may reject your emails outright, causing high bounce rates, or mark your domain as untrusted by spam filters, which hurts inbox placement. Over time, inconsistent delivery erodes sender reputation, and domain warming stalls because consistent sending is impossible.

Spam Filters and the SPF Lookup Limit

Every time an email arrives, receiving servers check your SPF record by performing DNS lookups. If your record includes multiple third-party services—like marketing platforms, email providers, or cloud infrastructures—each include statement counts toward a hard limit of 10 lookups. Exceeding this limit means the SPF check fails, and the server often rejects the message. This isn't a rare edge case—it's a core part of how SPF is designed to prevent abuse, per RFC 7208.

Even if your domain isn’t blacklisted, an SPF failure signals unreliable infrastructure to spam filters. This can lead to your messages being routed to spam folders or delayed. You might not get any bounce-back, making it hard to know the problem exists until your deliverability starts to drop.

Long-Term Damage to Sender Reputation

When SPF fails repeatedly across even a small subset of your campaigns, ISPs (like Gmail and Outlook) record that behavior. Over time, consistent failure correlates with poor sender reputation, especially if paired with high bounce rates. This damages your ability to reach inboxes—even with valid content.

Domain warming—slowly increasing email volume to build trust with providers—becomes nearly impossible if SPF is unstable. You can’t gradually grow your sending volume if the first few messages fail the SPF check. You’re stuck in a loop of failed sends and poor reputation signals.

Let's be clear: you don’t need every service you use to be listed in SPF. You can and should use a modern approach—aligning DKIM and DMARC correctly, and letting authenticated senders handle delivery. But many teams still rely on old SPF patterns without checking if their record is valid.

Use a real SPF record validation tool to scan your entire record, especially if you include multiple third parties. Tools like MailTester’s bulk verification tool can check your SPF setup, identify over-inclusion, and flag risky configurations—before they hit production.

For the full picture on how SPF, DKIM, and DMARC work together to protect deliverability, see the official SPF specification. The rules are strict for good reason—and you want to follow them.

Best Practices for Managing SPF with Multiple Include Statements

You can safely use multiple include statements in your SPF record, but only if you group shared services under a single, trusted third-party record, limit nesting to two levels, validate the full chain regularly, and always end with all or fail. This prevents exceeding the 10 lookup limit and reduces misalignment risks.

Optimize Include Statements for Clarity and Safety

  • Consolidate multiple marketing or service providers under one include (e.g., include:_spf.salesforce.com instead of separate includes for each tool) to reduce record complexity.
  • Only use an SPF aggregation record when absolutely necessary—aggregating records from multiple vendors increases the risk of exceeding the 10 DNS lookup limit defined in RFC 7208.
  • Never nest more than two levels deep (e.g., include:example.com → include:thirdparty.com → include:cloudprovider.com is acceptable, but three or more is not).
  • Use a dedicated SPF validation tool to audit your full chain weekly. This reveals hidden issues like expired includes, misconfigured domains, or unintended inclusions from compromised sources.

Ensure Proper Fallback Behavior

  • Always end your SPF record with all or fail to define how receivers should act when a message doesn’t match your policy. Using all allows delivery but may reduce signal strength; fail blocks delivery, helping prevent spoofing.
  • Test your SPF record in practice with inbox placement tools to confirm it doesn’t block legitimate mail. Some mail servers evaluate SPF during delivery, not just on receipt.
  • If you're managing multiple sender domains, consider using a unified verification tool to ensure all records are valid, correctly structured, and consistently applied across your infrastructure.

For teams managing large email lists, regular SPF validation is as important as DNS checks. Use the MailTester Inbox Placement tool to simulate real-world delivery conditions and catch SPF misconfigurations before they affect engagement.

Comparison of SPF Validation Tools: What You Need to Know

You need a tool that checks SPF syntax, recursively resolves every include statement, counts DNS lookups, and reports the exact failure point. Most tools stop at basic syntax checks. MailTester is the only one that verifies the full include chain, catches chain errors, and flags exceeding the 10-lookup limit—something Google, MxToolbox, and SPF Survey miss. This means you avoid false positives that let broken SPF records slip through.

Why Most SPF Tools Fall Short

SPF validation isn't just about syntax. It's about whether your full include chain resolves correctly. Many tools only validate the initial record, assuming include statements are safe. That’s a mistake. A single missing or malformed include can break your entire alignment.

Tool Validates Syntax Resolves Includes Recursively Counts DNS Lookups Flags Chain Failures Feedback Detail
MailTester Yes Yes — all include statements Yes — exact count per domain Yes — shows failing include chain Specific error types: include lookup limit exceeded, non-existent domain, unreachable DNS
MxToolbox Yes No — only checks top-level record No No Basic "valid" or "invalid" with no detail
Google Admin Toolbox Yes No No No Only confirms syntax; ignores include chains
SPF Survey Yes (per provider) No — no chain resolution No No Tests across providers but doesn’t debug fails

For example, if you include a domain like include:example.com and that domain has no TXT record, or it exceeds the 10-lookup limit, most tools won’t catch it. You’ll get a "valid" result—until your emails are rejected. RFC 7208 sets the 10-lookup limit; ignoring it breaks alignment.

How MailTester Fixes This

MailTester doesn’t stop at syntax. It follows every include chain, counts lookups, and returns the exact failure type. You learn why your SPF failed—whether it’s a DNS timeout, missing record, or lookup limit exceeded. This precision prevents delivery issues and reduces hard bounces.

Need to validate a list of domains with complex include chains? Use the bulk verification tool to catch failing records before deployment. Or integrate the real-time API into your onboarding flow. Always test delivery, too—check inbox placement with MailTester’s inbox tester.

Prevent SPF Failures Before They Happen

Use MailTester’s real-time verification API to catch SPF record issues early—before they cause bounces or damage your sender reputation. Validate your SPF configuration during campaign setup and check it weekly to catch drift from new tools or expired services. This proactive approach stops delivery problems before they impact your inbox placement.

Integrate SPF Validation Into Your Workflow

  • Use the MailTester Verification API to check SPF records automatically during campaign setup, not after.
  • Verify every domain with multiple include statements in your email infrastructure to ensure the total length stays below 250 characters—exceeding this limit triggers SPF fails.
  • Embed SPF checks in your pre-send validation pipeline, so only compliant addresses proceed to send.
  • Run weekly audits on your SPF records to detect drift from forgotten inclusions, expired third-party integrations, or misconfigured DNS updates.

Check for Real-World SPF Risks

  • Validate using real-world sender data—spfrecord.org and RFC 7208 document how SPF failures occur, especially when too many includes are chained.
  • Look for overuse of include: each one adds to the DNS lookup count; more than 10 can exceed limits and break SPF.
  • Confirm that your SPF record doesn’t rely on third-party domains unless they’re actively used and trusted—unverified or stale inclusions cause delivery drops.
  • Test with real email clients: use MailTester’s inbox placement testing to see how your SPF-compliant emails perform across Gmail, Outlook, and others.
SPF is one of the first filters mail receivers apply. A single misconfiguration can drop your deliverability rate by 20% or more, especially with high-volume senders.

SPF failures aren’t rare—most sender reputation issues trace back to misconfigured records. The real-time API lets you catch them before launch. No more guessing. No more post-send cleanup.

The Bottom Line: Don’t Guess—Validate Every SPF Change

SPF records with multiple include statements are inherently high-risk. A single broken or unreachable include can trigger complete delivery failures, even if the rest of the record is correct.

Manual checks or basic tools won’t catch these issues reliably. You need a validation tool that resolves each include, tracks DNS lookup counts, and ensures the total length stays under 255 characters—before you send.

MailTester’s SPF validation tool identifies broken includes, excessive lookups, and record size issues before they cause bounces, reduce inbox placement, or trigger spam filters.

Sources

Keep reading

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

Frequently asked questions

Can SPF records have multiple include statements?

Yes, but only if the total number of DNS lookups stays under 10 and the final SPF record size remains under 255 characters.

What happens if an SPF include statement fails?

The entire SPF validation fails. Most email providers reject the message or flag the sender as unreliable.

How many include statements can a valid SPF record have?

Up to 10 includes are allowed, but each counts as a DNS lookup. Overuse causes validation to fail.

Does MailTester check SPF record size and include count?

Yes. MailTester checks the total size after resolving all includes and counts the number of DNS lookups.

Can I use MailTester to test SPF before sending emails?

Yes. MailTester’s real-time API and bulk verification can test SPF records as part of your pre-send workflow.

Why do some tools say SPF is valid when it’s not?

Many tools only check syntax and don’t resolve include statements. They miss failures in the chain.

How often should I validate my SPF record?

At least once a month, or after adding new services that require SPF includes.

What's the difference between SPF and DKIM validation?

SPF validates sender identity through DNS lookup chains; DKIM validates message integrity via digital signatures.

Can you have multiple SPF records for one domain?

No. Having more than one SPF record causes a DNS syntax error and breaks SPF validation.

Does SPF affect deliverability?

Yes. Failed or broken SPF records reduce sender reputation and increase the chance of emails going to spam.

What does 'SPF fail' mean?

It means the sender domain’s SPF record failed verification. The email may be rejected or flagged as suspicious.

How do you fix an SPF record with too many includes?

Consolidate includes under a single trusted domain or reduce dependency on third-party SPF records.