Fix Sendinblue 450 4.7.1 SPF Errors | Email List Validation

What does Sendinblue's 450 4.7.1 error mean for your email delivery?

You sent a campaign. It looked right. Your list was clean. Yet the confirmation email still says “failed” with a 450 4.7.1 error from Sendinblue. No bounce back, no reason given — just a dry rejection. It’s frustrating, especially when you know nothing’s wrong with your message or your audience.

This error points to a technical issue buried in your domain’s setup: the Sender Policy Framework, or SPF. The receiving server explicitly blocked your email because Sendinblue isn’t authorized in your SPF record. Even if all your other deliverability settings are perfect, a missing or incorrect SPF entry will stop delivery cold.

SPF isn’t a marketing tactic. It’s a core part of email authentication — a technical gate that says, “only these servers can send from this domain.” When it’s wrong, even the most polished email campaign gets locked out.

Key takeaways

Sendinblue’s 450 4.7.1 error means the recipient’s mail server rejected your message due to an SPF failure.
SPF must explicitly include Sendinblue’s IP addresses or domain to authorize it to send emails on your behalf.
A broken SPF record will block delivery regardless of list quality, content, or sender reputation.

Why SPF is a critical layer in email deliverability

SPF is the first line of defense in email authentication. If your sender policy framework isn’t set up correctly, even a perfect email will be blocked before it reaches the inbox—regardless of content quality or sender reputation. Major providers like Gmail, Outlook, and Yahoo all check SPF as part of their spam filtering process.

How SPF fits into the bigger picture

SPF works alongside DKIM and DMARC to confirm your domain is authorized to send messages on behalf of a specific sender. Without SPF alignment, mail servers can’t verify whether your email came from an approved source, and they’ll treat it as suspicious or forged.

Think of SPF as a digital passport stamp: it says, “This message came from a server approved by the domain owner.” If the stamp is missing or invalid, the email likely gets rejected or flagged as spam before it ever hits the inbox.

Why SPF failures cause the 450 4.7.1 error in Sendinblue

When Sendinblue returns a 450 4.7.1 error, it means the receiving server rejected your message due to a failed SPF check. This often happens when your sending domain isn’t properly listed in the SPF record, or when you're using a third-party service (like Sendinblue) without including its IP addresses in your domain’s SPF policy.

The problem isn’t just technical—it’s reputational. Even one failed SPF check can hurt your sender reputation. Over time, inconsistent SPF records increase the risk of being flagged by filters or listed on blocklists.

According to RFC 7208 (the standard defining SPF), a valid SPF record must clearly list all authorized sending sources. If you send via email service providers, you need to ensure each one is included. If you're using multiple providers—like Sendinblue for campaigns and another for transactional email—each must be explicitly named in your SPF record.

It helps to test your SPF setup regularly. Tools like MXToolbox or Spamhaus can validate your record and highlight issues like oversized records or invalid syntax.

Once you verify your SPF is correctly configured, you reduce the risk of authentication failures and improve overall deliverability.

How SPF works: a technical breakdown without the jargon

When you send via Sendinblue, the receiving server checks your domain’s SPF record to see if Sendinblue’s IP addresses are explicitly allowed. If the record doesn’t list Sendinblue’s IPs or contains conflicting mechanisms like multiple include or all mechanisms, the server blocks the email with a 450 4.7.1 error. This isn’t about your content—it’s about server-level authentication failing.

SPF checks are automatic and strict

Every email sent through a service like Sendinblue is checked by the recipient’s mail server before delivery. The server looks up your domain’s SPF record in DNS—just like you’d look up a phone number. If Sendinblue’s IP ranges aren’t listed there, or if the record contradicts itself (e.g., both include:sendinblue.com and include:other-service.com without a consistent policy), the server rejects the message.

Think of SPF like a guest list at a door. If the sender (you) isn’t on the list, or if the list says “no one” but you’re listed anyway, you don’t get in. The error isn’t about spam or poor formatting—just whether the sending server was authorized to send on your behalf.

Common missteps and how to fix them

One common issue is having multiple SPF records for a single domain. Only one SPF record is allowed per domain. If you’ve added a new one without removing the old, conflicting record, the server sees that and returns a 450 4.7.1 error.

Another issue is using outdated or incorrect IPs. Sendinblue frequently updates its IP ranges. If your SPF record hasn’t been updated in months, it may no longer allow valid sending IPs. You can verify the current list via Sendinblue’s official documentation or the SPF RFC—the standard that defines how this works.

Lastly, avoid using mechanisms like all in a negative way (e.g., -all) without including all possible authorized senders. Overly restrictive policies block legitimate mail. Stick to a clear, single record that includes include:sendinblue.com and uses ~all (soft fail) for safer delivery.

Once the SPF record is correctly configured, your messages will no longer hit this error. Keep in mind that SPF is only one part of email authentication—DKIM and DMARC also matter. But fixing SPF properly is often the first step to stopping 450 4.7.1 bounces.

For deeper email list hygiene—like catching invalid addresses before they trigger bounces or reputation loss—consider validating your list beforehand. Bulk email list cleaning helps you send only to addresses that pass technical checks, reducing the odds of authentication errors and improving inbox placement.

The most common causes of Sendinblue 450 4.7.1 SPF errors

Sendinblue 450 4.7.1 errors usually mean your SPF record isn’t properly configured to allow Sendinblue’s sending IPs. Common issues include missing Sendinblue’s IP addresses, overlapping mechanisms, too many DNS lookups, or blocking legitimate senders by overly restrictive SPF policies. Let’s go through the real culprits you need to check.

Missing Sendinblue’s IP addresses in your SPF record

Sendinblue uses dynamic IP ranges to send emails. If your SPF record doesn’t include include:sendinblue.com, emails from their platform will fail SPF checks.
Always verify the current IP ranges via the official Sendinblue documentation or their help center—some IPs change over time.
Never rely on outdated guides or static IP lists; SPF records must reflect what’s active now.

Overlapping or contradictory SPF mechanisms

Using multiple include directives for overlapping services (like Sendinblue, Mailchimp, and AWS) can cause validation failures.
Never include more than one all mechanism—having both ~all and —all creates a conflict that breaks SPF.
Keep your SPF record simple: use include only for trusted services and avoid nesting complex conditions.

Exceeding the 10 DNS lookup limit

Each include or redirect directive counts as a DNS lookup. SPF allows a maximum of 10.
If you're using more than a few email services (Sendinblue, Salesforce, HubSpot, Klaviyo), you’ll likely hit this limit.
When you exceed 10 lookups, recipients treat the SPF check as "permerror" — the email gets rejected.
Use a dedicated SPF record manager or check your config with tools like MXToolbox to audit lookup counts.

Overly restrictive SPF records blocking multiple services

Some SPF records say include:sendinblue.com but don’t include other senders, like your CRM or transactional platform.
Having only one sender allowed means you can’t use multiple email tools without risk of rejection.
Use a single, shared SPF record that covers all necessary services—don’t lock yourself into a single sender.

SPF is designed for validation, not exclusivity. A correct record doesn’t block legitimate senders—it confirms them.

If you're unsure about your SPF setup, use a real-time email verification tool to check how your recipients see your messages. Verify emails in real time and test deliverability across providers before sending at scale.

How to check your SPF record for Sendinblue compatibility

If your Sendinblue emails are failing with a 450 4.7.1 error, it’s likely your SPF record doesn’t include Sendinblue’s authorized sending domains. You can fix this by verifying your SPF record contains include:_spf.sendinblue.com — and that it starts with v=spf1 without syntax errors or overly strict mechanisms like -all. Use a public DNS lookup tool to check this safely and quickly.

Check your SPF record step by step

Go to a public DNS lookup tool like MxToolbox or run dig TXT yourdomain.com in your terminal. Look for the TXT record that starts with v=spf1.
Check if include:_spf.sendinblue.com appears in the record. This is required for Sendinblue to pass SPF checks. Some older records may use include:sendinblue.com, but _spf.sendinblue.com is the current standard.
Ensure the record begins with v=spf1 and doesn’t start with something like spf1 or include alone. A missing or malformed version tag breaks SPF validation entirely.
Look for -all at the end of the record. If present, it means you’re rejecting all mail not explicitly listed. This blocks Sendinblue unless you add the correct include — and you risk breaking other legitimate services.
Limit the number of includes. SPF has a 10-lookup limit. Too many includes (including nested ones) can cause the check to fail, even if the syntax is correct.

Common pitfalls to avoid

SPF failures aren’t always about Sendinblue. A misconfigured record might block all sending, not just Sendinblue. If you’re using multiple email services (like Mailchimp, Salesforce, or SendGrid), each needs an include or the entire chain becomes invalid.

Use RFC 7208 as a reference for how SPF works — specifically section 5, which explains the syntax and mechanism order. A single typo, like forgetting the underscore in _spf.sendinblue.com, can break validation completely.

Once you’ve fixed your record, test it again using MxToolbox or a similar service. Don't guess — verify. You can double-check your domain’s email deliverability with a proven inbox placement test at inbox placement testing to confirm the fix resolved the issue.

How to fix your SPF record step by step

If you’re seeing a 450 4.7.1 error from Sendinblue, your SPF record is likely missing the include:_spf.sendinblue.com directive, or it’s malformed. Fix it by editing your domain’s DNS TXT record to include Sendinblue’s SPF, ensure only one TXT record exists per domain, and avoid multiple include or all mechanisms. Changes take 5–15 minutes to propagate.

Check and update your SPF record

Log in to your domain’s DNS provider — Cloudflare, GoDaddy, AWS Route 53, or another control panel.
Look for a TXT record with a name value of @ or www. This is your domain’s main SPF record.
If the record doesn’t already contain include:_spf.sendinblue.com, add it at the end of the existing content.
If you have multiple TXT records, merge them into one. Only one SPF record per domain is allowed — multiple records will break SPF.
Avoid adding multiple include directives, as this can trigger SPF failures. You should have only one all mechanism (typically ~all for soft-fail or -all for hard fail).
Save the change. DNS updates propagate in 5–15 minutes, but full global propagation can take up to 48 hours.

Verify the fix

After saving, use a real-time SPF validator like MXToolbox’s SPF Check to confirm your record is correct and includes Sendinblue’s include. You can also test with RFC 7208, the official SPF specification, to verify compliance.

The 6 steps described in “Check and update your SPF record”, in order.

Once the record is live, send a test email through Sendinblue. If the 450 4.7.1 error disappears, SPF is now correctly configured. If it persists, double-check for typos, duplicate records, or unexpected include chains.

For higher email deliverability, clean your list before sending. Invalid or poorly managed addresses can still trigger delivery issues even with correct SPF. Use a bulk email validation tool to remove bad addresses before sending: clean your list with real-time verification.

When to use SPF alignment: best practices for multi-service senders

You should use SPF alignment when sending email through multiple ESPs like SendGrid, Mailchimp, or Sendinblue. Each service’s IP ranges must be explicitly included in your SPF record using include or ip4 mechanisms. If your SPF record exceeds 10 DNS lookups, validation fails, leading to send failures like the 450 4.7.1 error. Keep it lean, centralized, and test every change.

Include each ESP’s IP ranges correctly

If you’re using multiple ESPs, don’t assume one record covers all. Each service requires its own authorization in your SPF policy. For example, Sendinblue’s sending IPs must be listed via include:_spf.sendinblue.com. Similarly, include Mailchimp’s include:_spf.mailchimp.com and SendGrid’s include:sendgrid.net. Skipping any results in failed SPF checks, even if the message is legitimate.

Each include or ip4 directive counts toward your 10-lookup limit. Too many lookups cause a permanent failure during DNS validation, which can trigger the 450 4.7.1 rejection. You can check your record’s lookup count using tools like MxToolbox or the SPF specification (RFC 7208), which defines this limit.

Reduce complexity with centralized management

Managing SPF for multiple platforms is error-prone. If you use more than three ESPs, consider a centralized DNS manager to avoid duplicate or conflicting entries. Tools like Cloudflare, Route 53, or a DNS provider with audit logs help track changes and reduce the chance of accidental over-inclusion.

Once your SPF record is stable and verified, move toward enforcing DMARC with a policy=reject setting. This allows you to monitor and block unauthenticated messages from third-party services. It’s not immediate—you need accurate SPF alignment first. Once in place, DMARC reduces phishing risk and improves inbox placement.

Still unsure if your emails are properly authenticated? You can validate SPF, DKIM, and DMARC in real time using our real-time verification API or test deliverability with our inbox-placement reports. Keep your email infrastructure clean, and avoid 450 4.7.1 errors before they happen.

SPF validation failures often stem not from misconfigured policies but from sending to invalid or high-risk addresses. Cleaning your list with email verification removes hard bounces, catch-all addresses, and disposable domains—common triggers of spam trap detection and sender reputation damage. A clean list reduces the number of failed delivery attempts, which indirectly protects your SPF alignment and lowers the chance of being flagged during validation. Learn more about email deliverability best practices from RFC 7208, the foundational specification for SPF.

Address quality impacts sender reputation

Every bounce, especially hard bounces, counts against your sender reputation. High bounce rates can signal poor list hygiene to ISPs and email providers, increasing the odds your messages get filtered—even if your SPF record is technically correct. You don’t need to worry about SPF if your entire list is invalid. Instead, validate before sending to ensure every address is real and likely to engage.

Verify before you send—real-time or in bulk

Using a real-time API or bulk verification tool before any campaign cleans out invalid addresses early. This includes identifying catch-all email addresses—where every input is accepted—commonly abused by bots or spam traps. Disposable domains, often used for temporary signups, rarely result in engagement and are often flagged as high-risk. Removing them helps maintain a healthy sending reputation.

Our real-time email verification API and bulk verification service confirm deliverability at scale, reducing bounce rates and protecting your sender reputation. Both tools integrate with platforms like Mailchimp, HubSpot, Klaviyo, and SendGrid—making it easy to clean lists before sending. A list that passes verification doesn’t just deliver better—it stays out of spam traps and protects your domain’s long-term deliverability.

What to do after fixing SPF for Sendinblue: verification steps

After updating your SPF record, wait 15–30 minutes for DNS propagation, then send a test email through your Sendinblue account to verify the 450 4.7.1 error is gone. Monitor deliverability metrics and check logs to confirm the fix took effect. You’re not done until the inbox placement improves and bounces stop.

Step-by-step verification process

Wait 15–30 minutes for DNS propagation
After updating your SPF record, DNS changes rarely take effect instantly. Mail servers cache DNS responses, so a 15-minute wait is standard, though propagation can take up to 30 minutes in some cases. Sending emails too soon risks seeing outdated records and false failures.
Test with a single email using inbox placement tools
Use a tool like our inbox placement feature to send a test message directly to Gmail, Outlook, and other major inboxes. This checks whether your email now lands in the inbox instead of spam or getting blocked. Some tools simulate real-world filtering behavior via authenticated test senders — a reliable way to verify delivery success [RFC 7208].
Monitor your deliverability dashboard
Check your Sendinblue analytics dashboard for drops in bounce rates and any new blocklist alerts. A stable or declining bounce ratio means your SPF changes are working. Persistent 450 4.7.1 errors after 30 minutes may point to misconfigured or overlapping SPF records.
Confirm the error disappears in send logs
Go to the Sendinblue email delivery logs and search for any remaining 450 4.7.1 entries. If the error is still present, review the full header of the failing message. Look for SPF evaluation steps and verify the domain is correctly listed in the published SPF record.

How to prevent future SPF issues

SPF records can break when adding or removing email services. Always test your SPF syntax before publishing — exceeding 10 mechanism lookups can cause failures. Use a tool like MXToolbox to validate your record’s structure and limit usage to a single, clean record per domain.

Once you’re confident the fix is working, run a bulk verification on your email list using real-time validation tools to catch invalid or risky addresses before sending. Poor list hygiene worsens sender reputation, even if SPF is correct. Clean your list before sending to reduce bounces and improve inbox placement.

Pro tip: use our inbox placement test to validate SPF success

If your Sendinblue 450 4.7.1 error persists after fixing SPF, don’t assume it’s resolved—test it with real mail. Our inbox placement test sends actual emails to Gmail, Outlook, and Yahoo, giving you exact results: whether your messages land in the inbox, spam, or are blocked. Only real-world delivery proof confirms your SPF is properly aligned.

Why internal testing isn’t enough

Testing SPF by sending a few messages to yourself or using a mock inbox won’t catch subtle alignment issues. Mail providers like Gmail don’t rely solely on SPF; they cross-check it with DKIM, DMARC, and sender reputation. A technical fix might pass internal checks but still fail in production.

Even if your bounce reports show no errors, SPF misconfigurations can cause delayed delivery or spam filtering. The only way to be sure is to send a message through a real inbox pipeline.

How inbox placement testing works

You send your message via our tool, and we route it to a curated set of real inboxes across Gmail, Outlook, and Yahoo. No fake addresses—each test mimics real-world delivery. Within minutes, you get a report showing status: delivered, spam, or blocked.

If your message now reaches the inbox, your SPF, DKIM, and DMARC configurations are in sync and accepted by major mail providers. That’s the real confirmation a fix worked—not a status code or a bounce.

As the Internet Society notes, SPF alignment is a key part of sender authentication, but enforcement varies across providers. A single test covering all major inboxes gives you far more reliability than checking logs or assuming alignment from syntax alone. The Internet Society discusses the evolving role of authentication in email delivery.

For the most accurate validation, pair this test with ongoing list hygiene. Use our inbox placement test to verify SPF, DMARC, and overall deliverability—before you send to your full list.

Why sender reputation isn’t just about content—SPF is foundational

Even a perfectly crafted email with personal, non-promotional content can be blocked if SPF is misconfigured. The 450 4.7.1 error is a clear signal: authentication failed at the protocol level.

Sender reputation isn't just about spam complaints or engagement. It's built on technical reliability. A flawed SPF record — whether too strict, overly permissive, or missing entirely — undermines trust with receivers, regardless of your message quality.

Prevent delivery failures before they happen. Verify your entire list at scale using automated tools that catch invalid, catch-all, and misconfigured addresses. Clean data reduces bounce rates and protects your sender reputation.

Keep reading

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

Frequently asked questions

Does the Sendinblue 450 4.7.1 error mean my email list is invalid?

No. This error is about authentication, not list quality. The issue lies in your SPF record, not your recipients’ addresses.

How long does it take for a fixed SPF record to take effect?

DNS changes typically propagate in 5 to 15 minutes. Allow 30 minutes to verify changes in email delivery systems.

Can I use multiple SPF records for different ESPs?

No. Only one SPF TXT record is allowed per domain. Combine all authorized services into a single record using 'include' directives.

What happens if I use 'all' with a hard fail (-all) in SPF?

It can accidentally block legitimate senders like Sendinblue if not configured carefully. Use soft fail (+all) temporarily only for testing.

It reduces bounce rates by filtering out invalid, catch-all, and disposable emails, which protects sender reputation and complements correct SPF setup.

Is SPF enough to guarantee inbox delivery?

No. SPF is one part of the authentication stack. DKIM and DMARC must also be set up correctly for full deliverability protection.

Should I check SPF during domain migration?

Yes. DNS changes during migration often break SPF records. Recheck and validate after transfer.

Can a shared IP address cause SPF errors with Sendinblue?

Only if the sender’s domain’s SPF record doesn’t include Sendinblue’s IP ranges. Shared IPs are normal—proper SPF inclusion is key.

What if my SPF record is over 10 DNS lookups?

Simplify by using 'include' directives sparingly or use DNS-based SPF record solutions like SPF chaining or aggregate records.

Does Sendinblue handle SPF for me?

No. Sendinblue acts as a sending service. Your domain’s SPF record must explicitly authorize it to send on your behalf.

How can I test if my SPF setup is working?

Use tools like MxToolbox SPF checker or our inbox placement test to simulate real-world delivery and validate SPF alignment.

What if my SPF fix doesn’t resolve the 450 4.7.1 error?

Check for typos, ensure only one SPF record exists, and test with multiple providers to isolate the issue to your domain or Sendinblue’s config.