Are your emails landing in spam or getting rejected without explanation? If yes, there's a good chance you’re dealing with an SPF authentication failed error.
SPF (Sender Policy Framework) is an essential email authentication protocol. When it fails, the receiving server can’t confirm that the message is coming from an authorized source. As a result, your emails are flagged as suspicious or completely blocked—impacting your ability to reach customers, leads, or partners.
The SPF authentication faiiled error is common, especially when using multiple email tools or sending emails on behalf of your domain through third-party services. Misconfigured SPF records or missing entries are often the cause.
In this article, we’ll break down:
- Why SPF authentication fails
- Common SPF authentication failed errors and what they mean
- Specific cases like SPF failed in Gmail and Outlook
- How to fix and prevent these issues
If email deliverability matters to your business, fixing SPF failures should be a priority.
What Is SPF Failure?
SPF failure occurs when the receiving server can't verify that an email was sent from an authorized source listed in your domain’s SPF record. This triggers the SPF authentication failed error and signals the server that the message might be suspicious.
SPF relies on DNS records where you define which mail servers are allowed to send emails on behalf of your domain. If the sending server isn’t listed there, the SPF check fails.
When this happens, one or more of the following things can happen:
- The email may land in the recipient’s spam or junk folder
- The server may reject the email completely
- Your domain reputation can take a hit over time
- Your email campaigns might experience low open and engagement rates
Emails landing in spam can be because of several other reasons apart from SPF authentication failed error. Read this blog to understand why emails land in spam.
So, it is good to analyze every error in detail to ensure that you have a clear understanding of why SPF is failing.
Types of SPF Failures
SPF doesn’t just return a pass or fail. It uses several result codes to indicate how the recipient server should treat the email.
These outcomes are determined by the qualifiers in your SPF record:
+ (Pass)
- (Fail)
~ (Softfail)
? (Neutral)
Each one leads to a different result during SPF authentication.
Let’s break them down:
1. SPF None
The SPF None error means the domain has no SPF record published. The server couldn't find any policy to check the authenticity of the sender.
Impact:
The recipient server treats the message as unauthenticated. It may not block it but could mark it as suspicious or spam.
Example of this error:
No v=spf1 record in DNS at all.
2. SPF Neutral (?)
The SPF Neutral error indicates that the domain owner explicitly says they are not stating whether the sender is authorized.
Impact:
Recipient servers make their own decision. Usually treated the same as a Softfail or None.
Example SPF Record:
v=spf1 ip4:192.168.0.1 ?all
This tells receiving servers: "I’m not saying if this IP is good or bad."
3. SPF Softfail (~)
SPF Softfall is when the sender is probably not authorized. It's a warning, not a hard block.
Impact:
Email might still be accepted but marked as suspicious or tagged as spam.
Example SPF Record:
v=spf1 include:_spf.example.com ~all
If the sender’s IP isn’t covered by the include, the message softfails.
4. SPF Fail (-) / Hardfail
In case of a hard SPF fail, the sender is explicitly unauthorized. The SPF record says the email must be rejected.
Impact:
Most servers will block or reject the email outright.
Example SPF Record:
v=spf1 include:_spf.example.com -all
If the IP doesn’t match, the email fails SPF and should be rejected.
5. SPF Temperror
SPF Temperror is a temporary DNS error occurred while trying to retrieve or check the SPF record. It’s not the sender’s fault.
Impact:
Recipient servers may choose to defer the message or retry later. Some may treat it as a softfail.
Example scenario:
DNS server timeout or misconfigured DNS zone during lookup.
6. SPF Permerror
A permanent error occurred while parsing or evaluating the SPF record. This usually means your SPF record is invalid.
Impact:
SPF fails completely. Recipient servers may treat this like a Hardfail.
Causes include:
- More than one SPF record
- Invalid syntax
- Too many DNS lookups (>10)
- Void lookups exceeding the limit
- Record length over limit
Now when you are aware of the types of SPF fails, let’s dig deeper to understand the errors and find fixes.
How To Fix Top SPF Authentication Failed Errors
Let’s look at some common errors you might encounter when the SPF fails. I have also listed the fixes for these errors:
1. No SPF Record in DNS
As we read in the previous section, SPF record not found is one of the basic SPF authentication failed errors you can encounter. This mainly happens when your domain doesn't have an SPF record set in the DNS and hence mail servers receiving your cold emails are unable to verify the sender’s legitimacy.
As a result the SPF fails, and your emails may get flagged as spoofed or unauthorized.
Fix:
Create and publish an SPF record in your domain’s DNS as a TXT record. Every domain provider - be it GoDaddy or Namecheap, provides DNS management settings. You just have to add a TXT record in your domain’s DNS settings. The overall procedure to add the record is quite simple and straightforward, but the location of the settings can change depending upon the provider’s user interface.
A SPF record will look like this:
v=spf1 include:yourprovider.com ~all
Alternatively, you can generate a SPF record.
Use a lookup tool (try this free SPF Lookup tool from Smartlead) to verify that your SPF record is visible and valid.
Read more on how to set up your SPF record.
2. Multiple SPF Records
SPF does not allow more than one record per domain.
If you create more than one SPF record—for example, one for Google Workspace and another for a marketing platform—email servers won’t be able to process them correctly. This leads to SPF failures, which can cause your emails to land in spam or get rejected entirely.
When a mail server checks your domain’s SPF record, it expects to find a single TXT record starting with v=spf1. If it finds more than one, it can’t decide which one to use, and the validation fails. This is known as a parsing error.
Example of an incorrect setup:
v=spf1 include:_spf.google.com ~all
v=spf1 include:mail.zendesk.com ~all
This is not valid. Both are separate SPF records.
Fix:
You need to merge all the entries into one single SPF record.
Here’s how:
- Use the include: mechanism to add external service providers (like Google, Zendesk, Mailchimp, etc.)
- Use ip4: (or ip6:) to list direct IP addresses that are authorized to send emails
- End the line with ~all or -all depending on your policy
Correct version:
v=spf1 include:_spf.google.com include:mail.zendesk.com ip4:192.0.2.1 ~all
This single SPF record authorizes:
- Google (via _spf.google.com)
- Zendesk (via mail.zendesk.com)
- A specific IP address (192.0.2.1)
3. Missing Sending IPs or Tools
When you use cold email tools, they usually send emails through their own servers or IP addresses. These tools don’t automatically get permission to send emails on behalf of your domain. If their sending infrastructure isn’t explicitly listed in your domain’s SPF record, any emails sent through them can fail SPF checks.
This results in poor deliverability, with messages ending up in spam folders or getting blocked entirely.
Fix:
Start by reviewing your cold email platform’s documentation or settings. Most tools will provide either:
- A domain to include in your SPF record (e.g., include:spf.provider.com)
- Or a list of IP addresses that need to be authorized (e.g., ip4:203.0.113.10)
Update your SPF record to include these values. This gives mail servers a clear signal that these platforms are allowed to send emails on your behalf.
Example SPF snippet:
v=spf1 include:spf.provider.com ~all
Don’t Forget Other Tools
It’s not just your cold email platform that needs to be included. Review all tools that send emails using your domain, including:
- CRM platforms that send transactional or follow-up emails
- Inbox warmers
- Email tracking and analytics tools
- Auto-reply or email handling services
Each of these may use different IPs or domains, and every one must be accounted for in your SPF record to avoid failures.
4. Exceeded 10 DNS Lookup Limit
SPF records have a strict limit: only 10 DNS lookups are allowed per check. This is part of the SPF specification and exists to prevent abuse and slowdowns during email authentication.
Each of the following adds to your lookup count:
- include: mechanisms (e.g., include:sendgrid.net)
- redirect=
- Any nested includes within those included domains
- a, mx, or ptr mechanisms that require DNS resolution
Even if your SPF record looks valid, going over 10 DNS lookups causes the SPF check to automatically fail.
This issue is common when:
- You use multiple email tools (CRM, marketing automation, cold outreach, support, etc.)
- Each tool adds an include: to your SPF record
- Some includes point to domains that themselves contain multiple other includes (nested lookups)
This means even 4–5 tools can push you over the 10-lookup limit.
Fix:
- Use SPF Flattening Tools
These tools resolve the includes to their underlying IP addresses and replace them in your SPF record. This reduces or eliminates DNS lookups.
Example tools: EasySPF, MXToolbox SPF Flattening, or your DNS provider’s built-in features.
- Remove Unused Services
Audit your SPF record and remove includes for platforms you no longer use. Every unnecessary include adds lookup weight.
- Prioritize Your Senders
If flattening isn’t an option, keep only the includes for services that handle the majority of your sending volume. You may need to move secondary tools to subdomains with their own SPF setup.
Alternatively, you can consider using secondary domains for your cold emails. This can help you manage SPF more efficiently. It keeps your primary domain’s SPF record lightweight and avoids hitting the 10-DNS lookup limit. This also prevents SPF failures from affecting your main email traffic.
5. Exceeded Void Lookup Limit (2)
When SPF processes your record, it performs DNS lookups for each include: or mechanism. Sometimes, a lookup points to a domain that doesn’t return any valid SPF data—this is called a void lookup.
Examples of void lookups:
- The domain no longer exists
- The domain exists but has no SPF record
- The SPF record is empty or invalid
SPF allows a maximum of 2 void lookups during validation. If your record triggers more than that, the entire SPF check fails, even if everything else is configured correctly.
Fix:
Use an SPF diagnostic or checker tool (like MXToolbox, DMARC Analyzer, or your DNS provider’s tool) to scan your current SPF setup. These tools will flag entries which include: entries are causing void lookups.
Once identified:
- Remove or replace the entries that no longer point to active services
- Check with your providers to ensure you’re using the correct include domains
- Avoid using outdated SPF includes from tools you no longer use or that have changed their infrastructure
6. Record Too Long or Broken by DNS
SPF TXT records must not exceed 255 characters in one string or 512 characters total. If too long, some DNS servers reject or misread them.
Fix:
Flatten your record and remove unnecessary or legacy entries. If your DNS host supports it, split the record into quoted strings (as permitted by RFC specs).
7. Syntax Errors
Typos, incorrect mechanisms, or invalid qualifiers can silently break your SPF record.
For example, using ip: instead of ip4:, or placing all before includes.
Fix:
Validate your record using a tool like EasyDMARC or SPF Surveyor. Follow correct syntax:
- v=spf1 must come first
- Use correct mechanisms like ip4:, ip6:, include:
- Only one all mechanism at the end
8. Misconfigured Subdomain or Mailbox
If you send cold emails from a subdomain (like outreach.domain.com) but the SPF record isn’t set for it, it might default to an empty or incorrect policy.
Fix:
Create a dedicated SPF record for each subdomain used. Don’t assume the root domain SPF applies unless explicitly configured.
9. ESP or SMTP Settings Misaligned
Sometimes, the email platform may send using internal relay servers or bounce handlers that aren’t listed in your SPF.
Even if the front-end tool looks legit, SPF fails in the background.
Fix:
Check your tool’s SMTP relay or mail agent settings. Ensure that SPF covers the actual envelope sender—not just the visible “From” address.
10. Poor Bounce Path Configuration
If your Return-Path or envelope sender is handled by a third-party domain (common in cold outreach), SPF can break because the bounce domain doesn’t match your DNS records.
Fix:
Customize the Return-Path to use your domain (e.g., bounces@yourdomain.com). Most cold email platforms offer a setting to configure this.
Next, let's learn how to fix SPF authentication failed error in Google Workspace.
Troubleshoot SPF issues in Google Workspace
If your cold emails are failing SPF checks or landing in spam, use these steps to identify and fix the issue.
1. Check Your SPF Record
Use the Google Admin Toolbox - Check MX to validate your SPF record.
Make sure:
- Your SPF record starts with v=spf1.
- It includes include:_spf.google.com for Gmail.
- You only have one SPF TXT record.
- It ends with a mechanism like ~all or -all.
Example:
v=spf1 include:_spf.google.com ip4:123.123.123.123 ~all
Include your sending tool’s IP or domain using ip4, ip6, or include.
2. Ensure Your Sending IP Is Authorized
If your cold email tool sends emails on your behalf, the sending IP must be listed in your SPF record.
Steps:
- Get the sending IP from your tool’s documentation or from the email header.
- Add it using the ip4: or include: mechanism in your SPF record.
- Wait up to 48 hours for DNS changes to propagate.
3. Avoid the DNS Lookup Limit
SPF supports a maximum of 10 DNS lookups. Exceeding this breaks authentication.
Each include, a, mx, or ptr adds to the count.
Fix it by:
- Removing unused includes.
- Flattening includes by replacing them with IP addresses.
- Using tools like SPF Flattening or DMARC Analyzer to simplify the record.
4. Inspect Message Headers for SPF Results
Send a test email and check the headers. Look for this line:
Authentication-Results: ... spf=pass / fail / softfail / neutral / temperror / permerror
What each result means:
- pass: SPF is working
- fail: The IP is not authorized
- softfail: IP not listed, but not strictly blocked
- neutral: No stance taken
- temperror: Temporary DNS issue
- permerror: SPF syntax error or too many lookups
Fix the record based on the result.
5. Avoid Common Mistakes
- Don’t use multiple SPF records—combine all into one.
- Don’t forget to include cold email platforms' sending IPs.
- Use ~all (softfail) if you’re still testing, and -all (fail) once confident.
Troubleshoot SPF issues in Outlook
If you use Outlook (Microsoft 365) for cold outreach and your emails are going to spam or failing SPF checks, follow these steps to fix it:
1. Make sure your SPF record includes Microsoft
For Outlook-based sending, your SPF record must include:
include:spf.protection.outlook.com
Example of a correct SPF record if you only send through Microsoft:
v=spf1 include:spf.protection.outlook.com -all
If you're also using a cold email tool, you need to include their sending IPs too.
Example:
v=spf1 include:spf.protection.outlook.com include:_spf.yourtool.com -all
2. Check for multiple SPF records
You should only have one SPF record per domain. If you have more than one, SPF will fail.
Fix: Merge all include: entries into a single SPF record.
3. Stay under the DNS lookup limit
SPF allows a maximum of 10 DNS lookups. Each include:, a, mx, or ptr counts as one.
Use a tool like MXToolbox to check how many lookups your record triggers.
Fix: Remove unnecessary include: mechanisms or flatten your SPF using tools like SPF Flattening from MXToolbox.
4. Inspect email headers for SPF results
Send a test email to a Gmail address, then view the full message headers.
Look for this line:
Authentication-Results: spf=
You’ll see one of these:
- spf=pass: Everything is working.
- spf=fail: The sender IP isn’t authorized in your SPF record.
- spf=softfail: The IP might not be listed, but wasn’t rejected.
- spf=neutral: No strong policy, borderline rejection.
- spf=none: No SPF record was found.
- spf=permerror: There’s a permanent error (e.g., invalid syntax).
- spf=temperror: Temporary DNS issue.
5. Make sure your outreach platform uses a custom domain
If your cold email tool sends using a shared domain, SPF won't fully align.
Use a custom domain that you control and configure SPF correctly for it.
Learn more about how to setup custom domain.
6. Wait for DNS changes to propagate
SPF updates might take a few minutes to a few hours. In some cases, up to 24–48 hours.
Final Thoughts on SPF Failures
SPF authentication failed errors are quite common but completely avoidable. SPF failures are one of the reasons your cold emails land in spam or get rejected. Most of the time, it's due to:
- Missing or misconfigured SPF records
- Not including your cold email platform in the SPF
- Hitting the DNS lookup limit
- Sending from domains you don't fully control
The good news? SPF authentication failed issues are fixable. By correctly setting up and maintaining your records, you give your emails the best shot at landing in the inbox.
Skip the SPF hassle with SmartSenders
If you're purchasing domains from SmartSenders (by Smartlead), you don't need to manually configure SPF, DKIM, or DMARC records. These domains come pre-configured and ready for warming up and sending. You can learn more about it here.
No guesswork, no DNS errors — just plug and start your outreach.
Author’s Details
Priya Abraham
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