Should you be concerned about '-all' in SPF records?
Matthew Whittaker
Co-founder & CTO, Suped
Published 13 Jul 2025
Updated 18 Aug 2025
7 min read
When configuring Sender Policy Framework (SPF) records, one of the most crucial decisions involves the use of the -all mechanism. This qualifier, often referred to as a "hard fail," signals to receiving mail servers that any email originating from an IP address not explicitly listed in your SPF record should be rejected. This strict policy can be a powerful tool for preventing email spoofing and ensuring that only authorized senders can use your domain.
However, its strictness also carries potential risks. Misconfigurations or incomplete SPF records that use -all can lead to legitimate emails being blocked by recipients, impacting your email deliverability. Understanding the nuances of -all and its interaction with other email authentication protocols like DMARC is key to striking the right balance between security and successful email delivery. This guide will explore whether you should be concerned about -all in your SPF records and how to implement it effectively.
Understanding the SPF record starts with its core purpose: to specify which mail servers are authorized to send email on behalf of your domain. It's essentially a DNS TXT record that lists these approved sending sources. The different qualifiers, like -all, dictate how receiving servers should treat emails that do not originate from these authorized sources.
A critical aspect of SPF is its mechanism qualifiers, which define the policy for unmatched senders. While -all enforces a strict "fail" policy, ~all (softfail) suggests that the email might be unauthorized but allows it to be delivered, often marked as spam. ?all (neutral) indicates no policy, essentially telling the receiving server to make its own decision. A less common one is +all (pass), which is dangerous and effectively opens up your domain to spoofing.
The choice of qualifier at the end of your SPF record, particularly between -all and ~all, has a significant impact on your email deliverability and how effectively you can protect your domain from impersonation. Many discussions revolve around whether to use -all or ~all in your SPF record. For a deeper dive into this, consider checking out this article on which SPF qualifier is better for email deliverability.
Example SPF Record
v=spf1 include:_spf.example.com -all
This example SPF record includes another SPF record and then uses -all to specify that any mail from other sources should strictly fail.
The sharp edge of -all: risks and rewards
Using -all provides the strongest stance against unauthorized senders, making it difficult for spammers and phishers to spoof your domain. When a mail server receives an email claiming to be from your domain but failing SPF with a -all policy, it is instructed to reject that email outright. This direct action significantly reduces the volume of fraudulent emails reaching inboxes, thereby protecting your brand reputation and recipients.
However, this strength is also its primary risk. If your SPF record is incomplete or incorrect, legitimate emails sent from services or platforms not listed in your record will be rejected. This can lead to significant deliverability issues, where important communications simply do not reach their intended recipients. It’s a common pitfall for organizations that frequently add new email sending services without updating their SPF record.
Benefits of using -all
Enhanced spoofing protection: Provides a strong defense against unauthorized use of your domain by explicitly instructing receiving servers to reject non-compliant emails.
Clear policy enforcement: Communicates a clear, unambiguous policy to email receivers, simplifying their decision-making process.
Improved DMARC effectiveness: Strengthens your DMARC policy by providing a definitive SPF authentication result, making it easier to move to stricter DMARC policies like p=quarantine or p=reject. You can find more information about safely transitioning your DMARC policy.
Risks of using -all
Potential for legitimate email rejection: Any legitimate email sent from a server not explicitly listed in your SPF record will be hard-failed and likely rejected by receiving servers.
Deliverability issues: Can lead to a significant drop in email deliverability if the SPF record isn't meticulously maintained and updated for all sending sources.
Complexity in management: Requires a comprehensive understanding of all email sending services used by your organization to avoid accidental rejections.
Strategic implementation of -all
The decision to use -all should not be taken lightly. It's generally recommended for organizations that have a complete and accurate inventory of all their email sending IP addresses and services. This level of control is crucial because any forgotten or incorrectly listed sending source will result in rejected emails. For domains that leverage many different third-party senders, like marketing platforms or transactional email services, maintaining an accurate SPF record with -all can be challenging.
Before deploying or switching to -all, it’s best practice to operate under a p=quarantine DMARC policy (or even p=none initially) to monitor your DMARC reports. These reports provide invaluable insight into which sources are sending email on behalf of your domain and how they are authenticating. This data helps you identify legitimate senders that might be missing from your SPF record before a hard fail policy impacts your deliverability. If you are starting with DMARC, here are some simple DMARC examples to guide you.
Best practices for deploying -all
Audit all sending sources: Identify every service or IP address that sends email on behalf of your domain. This includes marketing platforms, transactional email services, and internal mail servers.
Implement DMARC first: Begin with a DMARC policy of p=none to monitor traffic and ensure all legitimate sources are covered by SPF and DKIM before moving to a strict SPF -all policy. This allows you to collect DMARC reports and gain visibility.
Monitor DMARC reports diligently: Regularly review your DMARC reports to catch any authentication failures from legitimate sources and update your SPF record accordingly. This proactive monitoring is essential for maintaining email deliverability.
Stay within the 10-lookup limit: Be mindful of the SPF 10 DNS lookup limit, as exceeding it can cause SPF to fail, even with a correctly configured -all policy. Learn more about the 10 DNS lookups limit on SPF records.
Use an SPF flattener if needed: If your SPF record approaches the 10-lookup limit due to numerous include mechanisms, consider an SPF flattener to consolidate them. Read about best practices for SPF flatteners.
Ongoing management and impact on deliverability
Maintaining an SPF record with -all is not a set-it-and-forget-it task. As your organization adopts new email services or retires old ones, your SPF record will need updates. Neglecting these updates means risking legitimate emails being marked as spam or rejected outright. This is particularly crucial for transactional emails, such as password resets or order confirmations, where immediate delivery is vital.
The impact of a correctly implemented -all policy on email deliverability is generally positive, especially when coupled with DMARC. It signals to receiving mail servers (like those at Yahoo and Outlook) that your domain is serious about email security, which can improve your sender reputation. Conversely, misconfigured -all policies can lead to your domain being added to internal blocklists (or blacklists) by receiving mail servers, affecting future email campaigns. Monitoring your blocklist status is important.
Qualifier
Meaning
Impact on email delivery
-all
Hard fail: Emails from unauthorized IPs are rejected.
High security, but high risk of legitimate email rejection if SPF record is incomplete.
~all
Softfail: Emails from unauthorized IPs are accepted but marked suspicious (e.g., sent to spam).
Lower security than -all, but safer for domains with many sending sources or in transition. Can still land in spam.
?all
Neutral: No policy, receiving server makes its own decision.
Provides no security benefit, essentially an open policy.
+all
Pass: All emails are accepted, regardless of source.
Extremely dangerous, allows anyone to spoof your domain.
For domains without DMARC enabled, or those with DMARC set to p=none, ~all is often recommended as a safer starting point. This allows you to gather data on sending sources without immediately rejecting mail. However, for domains with a robust DMARC p=quarantine or p=reject policy in place, -all can be very effective as DMARC provides the overarching policy and reporting mechanism to catch any legitimate emails that SPF might incorrectly fail.
Views from the trenches
Best practices
Start with a more permissive SPF qualifier like ~all or implement DMARC with a p=none policy before moving to -all.
Pair -all with a strong DMARC policy (p=quarantine or p=reject) to maximize protection while maintaining visibility.
Use SPF flatteners if your record approaches the DNS lookup limit to prevent validation failures.
Common pitfalls
Forgetting to include all legitimate sending services in your SPF record, leading to legitimate email rejection.
Not monitoring DMARC reports after implementing -all, missing critical deliverability issues.
Exceeding the 10 DNS lookup limit, causing SPF validation failures even with a seemingly correct record.
Expert tips
Ensure comprehensive visibility into all email sending sources before implementing a hard fail SPF policy.
Utilize DMARC reporting to validate SPF configuration and identify any legitimate sending sources that might be missing.
Regularly review and update your SPF record to reflect changes in your email infrastructure and sending services.
Marketer view
Marketer from Email Geeks says they were concerned about a hard fail for -all but it turned out to be a misinterpretation of the report output, confirming that -all is generally acceptable.
May 15, 2024 - Email Geeks
Expert view
Expert from Email Geeks says that a '-all' mechanism typically means that emails not matching previous SPF terms will result in a hard fail, which is expected behavior and not a cause for concern in itself.
May 16, 2024 - Email Geeks
Conclusion: Balancing security with deliverability
While the -all mechanism in your SPF record provides the strongest possible enforcement against email spoofing, it demands meticulous attention to detail and ongoing management. Its ability to reject unauthorized emails outright is a powerful security feature, making it a valuable component in a robust email authentication strategy. However, this power comes with the responsibility of ensuring your SPF record is always up-to-date and comprehensive.
For organizations with tightly controlled sending environments and a mature DMARC implementation, -all is not only acceptable but highly recommended. It works in tandem with DMARC to provide clear instructions to receiving mail servers, enhancing your domain's reputation and reducing the threat of impersonation. If you're considering moving to -all, ensure you have a solid understanding of your sending infrastructure and are actively monitoring your DMARC reports to prevent any unintended deliverability issues.
Yahoo and 
Outlook) that your domain is serious about email security, which can improve your sender reputation. Conversely, misconfigured -all policies can lead to your domain being added to internal blocklists (or blacklists) by receiving mail servers, affecting future email campaigns. Monitoring your blocklist status is important.
