Have you ever sent an email only to find out it was rejected, marked as spam, or completely ignored? If so, you might be dealing with an SPF failure—a common email authentication issue that can silently undermine your email campaigns, customer communications, and business reputation.
SPF (Sender Policy Framework) is a critical security protocol that prevents spammers from faking your domain to send fraudulent emails. But when SPF isn’t configured correctly, even your legitimate emails can fail authentication, leading to bounces, spam filtering, or outright rejection by recipient servers.
The good news? SPF failures are fixable. This guide will walk you through the most common causes of SPF failures and provide clear, actionable solutions to ensure your emails reach their intended inboxes.
What is SPF Failure?
An SPF failure occurs when an email fails to pass SPF authentication, meaning the sending server is not listed as an authorized sender for the domain in the SPF record.
When this happens, recipient mail servers may:
- Reject the email outright (hard fail)
- Mark it as suspicious or spam (soft fail)
- Accept it but subject it to additional filtering
SPF failures typically result from misconfigured SPF records, unauthorized sending sources, or email forwarding issues. If left unresolved, they can significantly impact email deliverability, making it harder for your messages to reach their destination.
In the following sections, we’ll break down the top reasons SPF failures happen and how to fix them effectively.
Top Causes of SPF Failures and How to Fix Them
Let’s talk about some of the culprits that could derail your email’s path to the inbox.
1. Missing SPF Record
When receiving mail servers fail to find an SPF record published in your DNS, they have no policy to reference during authentication. As a result, emails from this domain might fail SPF authentication checks, leading to potential delivery issues or being flagged as suspicious.
Solution:
If your domain doesn’t have an SPF record, adding one is straightforward, even if you have no prior experience. Follow these steps:
Step 1: Use an SPF checker tool (e.g., MXToolbox SPF Lookup or Google’s Admin Toolbox) to confirm whether you have an SPF record. If not, you’ll need to create a new one.
Step 2: Create a New SPF Record
SPF records are stored in your domain’s DNS settings as a TXT record. Depending on your mail service, your SPF record should look like this:
| Google Workspace | v=spf1 include:_spf.google.com ~all |
| Microsoft 365 (Outlook) | v=spf1 include:spf.protection.outlook.com -all |
| Multiple Mail Services | v=spf1 include:_spf.google.com include:mailgun.org include:sendgrid.net ~all |
Step 3: Add the SPF Record to Your DNS Settings
- Log into your domain provider’s dashboard (e.g., GoDaddy, Cloudflare, or wherever your domain’s DNS is managed).
- Find the DNS settings or DNS Management section.
- Click Add a new record, then select TXT Record.
- Enter the following:
- Host: @ (or your domain name, depending on the provider)
- Type: TXT
- Value: Paste the SPF record you created (e.g., v=spf1 include:_spf.google.com ~all).
- TTL: Leave it as default (or set to 3600 seconds).
5. Save the changes.
Step 4: Verify Your SPF Record
Wait a few minutes to a few hours for DNS changes to propagate, then use an SPF validation tool like MXToolbox to check if your SPF record is correctly published.
2. Multiple SPF Records
Having multiple SPF records for a single domain can lead to SPF authentication failures. Multiple SPF records can confuse receiving servers, as they’re unsure which record to consider. This ambiguity often results in SPF failures, as the receiving server may not interpret the intended policy correctly.
Solution:
Merge all SPF entries into a single record. Delete any duplicate records and combine multiple entries into one, ensuring all authorized servers are included. Test your new SPF record using SPF validation tools.
| Common SPF Issue | Incorrect SPF record | Fixed SPF record |
| Multiple SPF records | v=spf1 include:_spf.google.com -all v=spf1 include:spf.mailgun.org -all | v=spf1 include:_spf.google.com include:spf.mailgun.org -all |
3. Too Many DNS Lookups
When an email is sent, SPF checks if the sender is allowed to use that domain by looking up a list of approved mail servers (stored in the domain’s DNS records). However, SPF has a limit—it can only perform 10 lookups per email.
If your SPF txt record is too complex, with too many rules or indirect references to other servers, it may require more than 10 lookups. When this happens, the email provider stops checking and assumes the email is not verified, leading to SPF failure.
Solution:
- Remove unnecessary “include” entries. Each “include” statement in your SPF record adds a DNS lookup. Many businesses use multiple email providers (Google, Outlook, Mailchimp, etc.), which can push them over the limit.
- Use SPF compression services like SPF Flattening (e.g., MXToolbox) to combine includes into a smaller list.
| Common SPF Issue | Incorrect SPF record | Fixed SPF record |
| Too Many DNS Lookups | v=spf1 include:_spf.google.com include:spf.mailgun.org include:spf.sendgrid.net include:spf.salesforce.com include:spf.constantcontact.com -all | v=spf1 include:_spf.google.com include:spf.mailgun.org -all |
4. Syntax Errors
Syntax errors in SPF records—such as typos, misplaced characters, or invalid syntax—can cause authentication failures. Always verify SPF formatting using an SPF validation tool before applying changes.
Solution:
Follow correct SPF syntax rules.
| Common SPF Issue | Incorrect SPF record | Fixed SPF record |
| Syntax errors | v=spf1 include:_spf.google.com include:spf.mailgun.org all | v=spf1 include:_spf.google.com include:spf.mailgun.org -all |
Related: Mastering SPF Syntax: A Step-by-Step Guide
5. Exceeding SPF Character Limits
SPF records have a maximum length of 255 characters in a single DNS TXT record. Exceeding this limit can cause SPF parsing errors.
Solution:
Each “include” statement adds characters. If you’ve added too many email services, your SPF record may become too long. If you’ve stopped using an email provider, remove its “include” entry from your SPF record.
6. Email Service Provider Settings
Incorrect or misconfigured settings within the email service provider’s platform can result in failure in SPF alignment, particularly if the provider’s configuration doesn’t align with the domain’s SPF record.
Solution:
Check your provider’s official SPF setup guide (e.g., Google, Microsoft, Mailgun).
7. Poor Bounce Management
When an email bounces (fails to be delivered), the receiving server may send a rejection message back to the sender. Some email services forward these bounce messages using a different mail server, which can change the technical details of the original email (SPF headers).
Since SPF verifies that emails come from authorized servers, this modification can make it seem like the email was sent from an unauthorized source, leading to an SPF failure.
Solution:
If you use an email service provider (ESP) like Google Workspace, Mailgun, or SendGrid, they usually provide instructions on how to set your Return-Path correctly.
| Common SPF Issue | Incorrect SPF record | Fixed SPF record |
| Poor bounce management | Return-Path: bounces.externaldomain.com | Return-Path: bounce@yourdomain.com |
8. Invalid Macros
SPF records can use macros to add information like the sender’s IP address or domain during authentication. However, if these macros are set up incorrectly—whether through invalid syntax or improper formatting—SPF authentication can fail.
That’s why you need to make sure your macros follow SPF specifications and are correctly structured. Regularly testing your SPF setup can help catch and fix any macro-related issues before they cause issues to your email deliverability.
Solution:
Check if your email provider supports SPF macros—if not, remove them.
- Make sure lookup records exist for macros like “exists:%{i}.spf.example.com”.
- Test your SPF record using validation tools to catch formatting issues.
- If macros are causing issues, replace them with standard SPF mechanisms like include: or direct IP addresses.
| Common SPF Issue | Incorrect SPF record | Fixed SPF record |
| Invalid Macros | v=spf1 exists:%{i}.spf.example.com -all | v=spf1 include:_spf.example.com -all |
Even with a perfect SPF record, email reputation plays a critical role in inbox placement. InboxAlly helps boost sender reputation, reduce spam flagging, and improve email deliverability—ensuring your emails consistently land in the inbox.
Final Thoughts
SPF authentication issues can be annoying. Left unchecked, they open the door to spoofing, phishing, and endless email deliverability headaches. But with the right fixes—clean DNS records and proper header alignment—you can turn it all around. Email success is in the details, and it’s well worth the effort.
And if sorting through endless headers and DNS records feels a bit too much, don’t sweat it. InboxAlly is built to simplify email deliverability, help you boost your sender reputation, and keep your emails out of spam for good. Ready to take control? Learn how InboxAlly can put your business to the next level!
FAQs – SPF Records
What is DMARC, SPF, and DKIM alignment, and why does it matter?
DMARC relies on two email authentication protocols: SPF and DKIM (DomainKeys Identified Mail). DMARC alignment verifies that the sender’s domain is authenticated, confirming the email’s legitimacy and potentially boosting deliverability.
SPF aligns with the domain in the “Return-Path” header, while DKIM aligns with the “DKIM-Signature” header. Both must match the domain in the “From:” header to achieve DMARC alignment.
For SPF alignment, the focus is on two key headers:
- The “From:” header
- The “Return-Path” header
SPF alignment requires these headers to sync, ensuring that the domains match and validate the sender’s authenticity. Misalignment can lead to failed DMARC checks, affecting email trust and deliverability.
Does SPF failure always indicate malicious activity?
Not necessarily. While SPF failure can sometimes indicate malicious activity, it can also occur for innocent reasons, such as misconfiguration or legitimate email forwarding practices. However, it’s essential to investigate and address SPF failures promptly to maintain email security.
How does SPF failure affect email deliverability rates?
An “SPF fail” can harm email deliverability rates. Emails that fail SPF checks are more likely to be filtered out as spam by recipient mail servers, which can reduce the effectiveness of email marketing campaigns and communication efforts.
How often should I review my SPF records?
Regularly reviewing and updating an SPF DNS record is recommended, especially when changing mail server configurations or adding new mail services. Regular reviews help ensure that SPF records accurately reflect authorized mail servers and minimize the risk of SPF authentication fails.
Are there any tools to help diagnose SPF issues?
Yes, several tools, such as SPF validators or SPF record checkers, are available online to help diagnose SPF validation errors. These tools can analyze SPF records, verify DNS configurations, and identify potential problems causing SPF failure.
What are SPF Qualifiers?
SPF qualifiers define how Mail Transfer Agents (MTAs) handle emails based on authentication results.
SPF Pass (+all) – The sender’s IP is authorized, and the email is accepted.
SPF Neutral (?all) – The SPF record does not explicitly approve or reject the sender. The recipient’s server decides how to handle the email.
SPF Soft Fail (~all) – The sender is not explicitly authorized, but the email is still accepted, often flagged for further scrutiny.
SPF Hard Fail (-all) – The sender is unauthorized, and the email is rejected outright.
SPF TempError – A temporary error (e.g., DNS timeout) prevents SPF validation, and the email may be retried later.
SPF PermError – A permanent SPF configuration error (e.g., syntax issue, exceeding DNS lookup limits) that requires correction before authentication can proceed.
A properly configured SPF record helps ensure email deliverability and prevents spoofing.