Summary
Understanding SPF (Sender Policy Framework) qualifiers is essential for effective email deliverability and preventing spoofing. These qualifiers, such as '+all', '-all', '~all', and '?all', dictate how receiving mail servers should interpret and act upon emails that either pass or fail the SPF authentication check for your domain. Incorrect use of these qualifiers can severely impact your email's ability to reach the inbox, potentially leading to messages being marked as spam or outright rejected.
Key findings
- Neutral result: The ?all qualifier results in a 'neutral' SPF outcome, meaning no definite assertion (positive or negative) is made about the sending client. This effectively renders the SPF record inactive for enforcement purposes.
- Functionally inactive: A 'neutral' result is treated the same as a 'none' result by recipients, indicating that SPF is not actively providing a policy for unauthorized senders. This means emails from unauthorized sources might still be accepted without specific flags.
- Enforcement levels: For SPF to have any real impact on email authentication and deliverability, the record must end with either ~all (softfail) or -all (fail).
- Strictness vs. flexibility: The choice between ~all and -all largely depends on your domain's sending practices and risk tolerance. While -all offers stricter protection, it can lead to legitimate emails being rejected if not perfectly configured. For more details on this choice, refer to our guide on SPF ~all vs -all.
Key considerations
- Avoid ?all: Unless you are in a very specific testing phase, ?all should not be used in a production SPF record as it negates the security benefits of SPF.
- Avoid +all: +all explicitly allows any server to send mail on behalf of your domain, making it highly susceptible to spoofing and often leading to emails being marked as spam or blocklisted.
- Best practice: Most domains should aim for ~all as a starting point, transitioning to -all only when they have a comprehensive understanding of all their sending sources, often achieved through DMARC reporting and monitoring. The RFC documentation clarifies the definitions of these results.
- DMARC interaction: Even with ?all or ~all, a DMARC policy (especially at p=reject or p=quarantine) will still enforce policies based on SPF alignment. However, the SPF qualifier itself plays a critical role in the initial authentication signal. The IETF RFC 7208 provides a comprehensive overview of SPF, including its section on results.
What email marketers say
Email marketers often approach SPF qualifiers from a pragmatic perspective, focusing on what works best for deliverability while minimizing the risk of legitimate emails being blocked. Their opinions highlight the importance of balancing strict security with the practicalities of sending email through various platforms. They frequently discuss the impact of each qualifier on inbox placement and the necessity of proper configuration.
Key opinions
- Testing vs. production: The ?all qualifier is seen as suitable only for testing SPF records on non-production domains, as it essentially makes the record inactive for enforcement.
- Impact of +all: Using +all is widely considered detrimental to deliverability, as it signals that any server is authorized to send email for the domain, significantly increasing spam scores.
- Production standard: Marketers recognize that for any enforcement or deliverability benefit, a production SPF record must end with either ~all or -all. Most start with ~all for its balance of security and flexibility.
- Overly broad records: Some mailbox providers (MBPs) may treat overly broad SPF records, such as those using +all, differently than intended, potentially leading to increased spam classifications. This highlights the need for careful configuration when setting up your SPF TXT record.
Key considerations
- Prioritize enforcement: If you want SPF to be effective in preventing spoofing and improving deliverability, ensure your record ends with ~all or -all.
- Monitor performance: Regularly check your email deliverability and authentication reports to understand how different qualifiers impact your sender reputation. While SPF is crucial, it's just one part of overall email deliverability strategy.
- DMARC integration: Use DMARC in conjunction with SPF and DKIM for comprehensive email authentication. DMARC policies provide instructions on how receiving servers should handle emails that fail authentication, giving you greater control. Learn more about DMARC, SPF, and DKIM.
Marketer view
An email marketer from Email Geeks discussed the behavior of the ?all qualifier. They explained that it means a failure should be treated as a neutral result. While not technically inactive, for most receivers, it functions as good as inactive.Essentially, this qualifier provides no clear directive to receiving servers regarding emails that do not match the specified SPF mechanisms. Therefore, it offers little to no protection against email spoofing or unauthorized sending.
Marketer view
An email marketer from Email Geeks outlined the various SPF qualifiers and their meanings. They clarified that +all means a 'pass', allowing all mail. For -all, it's a 'fail', only allowing mail that matches parameters in the record.They also mentioned ~all as a 'softfail', allowing mail whether or not it matches, and ?all as 'neutral', indicating no policy statement. This distinction is crucial for understanding the enforcement level of your SPF record.
What the experts say
Deliverability experts bring a deep technical and operational understanding to SPF qualifiers, often drawing from extensive experience with mailbox providers and RFC specifications. Their insights highlight potential pitfalls, best practices, and the subtle nuances in how different email systems interpret SPF policies. They often stress the importance of robust authentication for maintaining sender reputation and avoiding blocklists.
Key opinions
- Neutral as 'none': Experts confirm that a 'neutral' SPF result (from ?all) must be treated exactly like a 'none' result, effectively meaning there is no definite policy assertion.
- Functional inactivity: While ?all isn't literally inactive, experts agree it's functionally the same for most receivers, offering no real protection or enforcement.
- Misuse of ?all: The use of ?all is often interpreted as a sign of poor configuration or a lack of understanding of SPF, and should be avoided in production.
- Risks of +all: Experts strongly advise against +all, as it essentially invalidates SPF's purpose and can lead to emails being heavily penalized or classified as spam. Learn how this can contribute to emails going to spam.
Key considerations
- Default to ~all: The consensus among experts is to use ~all as the standard qualifier. It provides a good balance, marking non-compliant emails as 'softfail' while reducing the risk of legitimate emails being dropped compared to -all.
- Understand implications: Before implementing -all, ensure all legitimate sending sources are explicitly included in your SPF record to prevent delivery failures. This meticulous approach helps prevent intermittent email delivery failures.
- DMARC's role: While SPF qualifiers provide immediate instructions, DMARC can layer on top to provide a more robust policy for handling SPF authentication failures. Even if an SPF qualifier might contradict a DMARC policy in theory, operational systems might treat them similarly for DMARC evaluation. For a deeper understanding of this interaction, consider consulting the SPF record syntax.
Expert view
A deliverability expert from Email Geeks clarified that if you want any enforcement from SPF, your record must end with either ~all or -all. They stressed that without one of these, SPF will not be utilized by the receiver.This confirms that qualifiers are not merely suggestions but crucial directives that determine whether receiving mail servers apply any policy based on SPF authentication, effectively defining its role in preventing unauthorized sending.
Expert view
A deliverability expert from Email Geeks firmly stated that ?all is SPF speak for I don't know what I'm doing and should never be in a real record. They also added that +all means I know what SPF is, and I'll have no truck with it.This strong opinion from an experienced professional underscores the significant negative implications of using permissive or undefined SPF qualifiers. They effectively dismantle the security benefits that SPF is designed to provide, opening the door for widespread spoofing and damage to sender reputation.
What the documentation says
Official documentation, primarily RFC 7208, defines the precise meaning and intended behavior of SPF qualifiers. These documents serve as the foundational source for how SPF should be implemented and interpreted by mail servers globally. Understanding the RFC provides the definitive technical perspective, often contrasting with common misconceptions or operational realities.
Key findings
- Result definitions: The RFC clearly defines the four main SPF results corresponding to the qualifiers: Pass (+all), Fail (-all), SoftFail (~all), and Neutral (?all).
- Neutral's equivalence: RFC 7208 explicitly states that a neutral result must be treated exactly like the none result, existing only for informational purposes rather than enforcement. This reinforces that ?all offers no policy.
- Default pass: If no qualifier is explicitly stated for a mechanism, the default qualifier is +all (pass), meaning it will allow mail from that source. This underlines the importance of explicitly stating qualifiers for desired policy outcomes.
- Policy application: The RFC details how each qualifier influences the receiving server's decision, from outright acceptance with +all to definitive rejection with -all. This technical framework is crucial for anyone looking to understand the full form of SPF.
Key considerations
- RFC compliance: Adhering to RFC specifications is paramount for ensuring interoperability and expected behavior across various mail systems. Deviations can lead to unpredictable deliverability issues.
- Security implications: Documentation highlights that only -all and ~all provide a policy that can prevent unauthorized sending, with -all being the strongest. The others (e.g., +all, ?all) offer no meaningful protection against spoofing. This is crucial for understanding how SPF record syntax impacts security.
- Interaction with DMARC: While RFCs primarily define SPF's standalone behavior, it's understood that DMARC builds upon these results. A neutral SPF result may lead DMARC to rely solely on DKIM for authentication or apply a 'none' policy.
Technical article
RFC 7208, section 8.2 on SPF results, describes a neutral result. This indicates that although a policy for the identity was discovered, there is no definite assertion, either positive or negative, regarding the client's authorization.Furthermore, the RFC mandates that a neutral result must be treated exactly like a none result; the distinction exists purely for informational purposes. This clarifies that ?all provides no active enforcement.
Technical article
The DreamHost documentation on adding an SPF record includes a specific interpretation of the ?all qualifier. It states that the question mark makes the entire SPF record inactive, as though the domain had no SPF record at all.This operational guidance from a hosting provider reinforces the practical effect of ?all. It suggests that for all practical purposes, a record ending in ?all provides no authentication signal to receiving mail servers, thus offering no protection against spoofing.
Related resources
13 resources
Related pages
SPF ~all vs -all: Which is better for email deliverability and spoofing protection?
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How to format SPF TXT records, add domain includes, and avoid DNS size issues?
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