Should I use ~all or -all in my SPF record?

Key findings

• DMARC primacy: With a DMARC policy of p=reject or p=quarantine, the specific SPF qualifier (~all vs. -all) often has minimal impact on enforcement actions, as DMARC dictates the ultimate outcome.
• Receiver behavior: Many mail receivers treat ~all the same as neutral, and some even treat -all as a softfail, especially if DMARC is not configured.
• Spoofing protection: SPF alone does not fully prevent email spoofing, particularly of the From: header, which is addressed by DMARC alignment.
• Ease of deployment: Using ~all can be safer during initial SPF setup or when changes are frequent, as it is less likely to cause legitimate emails to be rejected if configurations are not perfect.
• Outdated advice: Recommendations to strictly use -all without considering DMARC may be based on older security practices.

Key considerations

• DMARC implementation: If you have a strong DMARC policy (e.g., p=reject), the choice of ~all or -all for SPF typically doesn't affect the final delivery outcome, as DMARC will enforce the policy.
• No DMARC: If DMARC is not implemented, -all offers stricter enforcement for unauthorized senders. However, it carries a higher risk of legitimate mail being rejected if your SPF record is incomplete or incorrect. Review the Word to the Wise article for more insights.
• Domain reputation: Regardless of the qualifier, having a published SPF record is considered a best practice for email deliverability and domain reputation.
• Testing: Always thoroughly test your SPF record, especially when making changes, to ensure proper authentication and prevent legitimate emails from being flagged as spam or rejected.

Key opinions

• DMARC mitigates SPF differences: Many marketers believe that with DMARC in place, the distinction between ~all and -all becomes largely irrelevant for email deliverability.
• Avoiding hard fails: Some marketers prefer ~all to reduce the risk of legitimate emails being hard-rejected due to misconfigurations or unexpected changes from hosting providers.
• Third-party services: Integrating SPF with multiple third-party sending services (like marketing automation platforms) can introduce complexities, sometimes leading to unexpected SPF verification failures if not carefully managed.
• Consultant skepticism: Some marketers express caution regarding unsolicited advice from security specialists or consultants who may overstate issues to sell their services.

Key considerations

• SPF record management: Ensure your SPF record is correctly formatted and includes all legitimate sending sources to avoid deliverability problems, regardless of the all qualifier used.
• DMARC integration: If you are concerned about spoofing and strict enforcement, focus on implementing DMARC with a policy of p=quarantine or p=reject.
• Hosting provider nuances: Be aware that some web hosting services or email providers may interpret -all differently or apply stricter rules than expected, potentially leading to delivery issues.
• Test before deploying: Always conduct thorough testing when modifying SPF records to prevent unintended consequences on your email campaigns.

Key opinions

• Minimal difference with DMARC: Many experts state that if DMARC is properly implemented with a strong enforcement policy (like p=reject), the choice between ~all and -all in SPF largely becomes negligible.
• SPF's primary role: SPF is crucial for authenticating the Return-Path domain, but alone, it doesn't fully prevent header spoofing.
• Safety of ~all: Some recommend ~all as a safer default, especially if there's any uncertainty about the completeness of the SPF record or how various receiving servers will interpret a hardfail.
• Receiver variation: Mail receivers' actual treatment of ~all and -all can vary, with some treating softfail like neutral and hardfail like softfail.
• Non-sending domains: For domains that should not send email, a strict v=spf1 -all is the recommended best practice to prevent unauthorized use.

Key considerations

• Align with DMARC: If DMARC is already at p=reject, using ~all in SPF is often the pragmatic choice, as DMARC will enforce the rejection policy anyway.
• Publish SPF records: Regardless of the qualifier, publishing an SPF record is a fundamental step for email authentication and is now considered a general best practice.
• Assess current infrastructure: Before switching to -all, especially without DMARC, ensure all legitimate sending IP addresses and includes are accounted for to prevent deliverability issues. Read more about SPF qualifiers.
• Use for non-sending domains: For domains that should never send email, v=spf1 -all is the appropriate and most secure SPF record configuration, as discussed in the context of DMARC, SPF, and DKIM for non-sending domains.

Key findings

• SPF definition: SPF enables domain owners to explicitly define which IP addresses are authorized to send email from their domain, as specified in RFC 7208.
• Fail (-all): A -all result is an explicit statement that the sending client is unauthorized to use the domain in the given identity, indicating a strong recommendation for rejection.
• Softfail (~all): A ~all result indicates that the SPF validator has doubts about the message's authenticity, but it's not a definitive fail, suggesting a soft rejection or further scrutiny.
• All mechanism: The all mechanism is a common way to end an SPF record, indicating that all other mechanisms have been evaluated, and this final mechanism matches any remaining IP addresses.

Key considerations

• RFC compliance: Adhering to the specifications in RFC 7208 is crucial for proper SPF implementation and interoperability across mail systems.
• Interaction with DMARC: While RFC 7208 defines SPF, the interaction of SPF results with DMARC policies (RFC 7489) is what truly determines the ultimate delivery action for unauthenticated mail.
• Error handling: Using -all without DMARC p=reject can lead to hard rejections of legitimate emails if your SPF record has any omissions or errors.
• Policy enforcement: The RFC states the intended meaning of ~all and -all, but how receiving servers interpret and act upon these recommendations can vary in practice.