Why do some ESPs recommend SPF records when they are not needed?

Key findings

• SPF validation: SPF primarily authenticates the Mail From (or Return-Path) domain, which is often an ESP's subdomain, not your visible From domain.
• DNS lookup limit: Adding multiple include mechanisms to your SPF record can quickly exceed the 10 DNS lookup limit, causing SPF validation failures (PermError).
• Legacy advice: Many ESPs, including major ones, have historically (and sometimes still) provided outdated documentation recommending unnecessary SPF inclusions for the visible From domain.
• Authentication practices: Modern email authentication relies more heavily on DKIM and DMARC for aligning the visible From domain.

Key considerations

• Review SPF records: Regularly audit your domain's SPF record to ensure it's concise, accurate, and does not exceed the 10 DNS lookup limit. If using an ESP that handles SPF on their own return-path domain, you likely don't need their specific SPF include.
• Prioritize DMARC and DKIM: Focus on correctly setting up DKIM for your sending domain and implementing a DMARC policy. These protocols are more effective for domain alignment and preventing spoofing of your visible From address.
• Educate your team: Ensure that anyone managing your email infrastructure understands the nuances of SPF, DKIM, and DMARC, particularly the distinction between the Mail From and From domains.
• Consult authoritative sources: When in doubt, refer to RFCs or reputable deliverability resources that provide clear guidance on SPF implementation, such as dmarcian.com.

Key opinions

• Client education: Marketers often struggle to convince non-technical clients about proper SPF configuration due to the abundance of conflicting and incorrect information online.
• Misleading documentation: Many ESPs provide legacy documentation that advises adding specific SPF records for the visible From domain, even when it's not needed for authentication and can cause DNS lookup issues.
• Authentication evolution: Some ESPs have updated their authentication recommendations to focus on DKIM CNAME records rather than direct SPF inclusions, but widespread awareness is still lacking.
• Impact on deliverability: Incorrect SPF setups, particularly those exceeding the 10 DNS lookup limit, can negatively impact email deliverability by causing authentication failures.

Key considerations

• Prioritize up-to-date guidance: Seek the most current authentication setup instructions from your ESP, often focusing on DKIM and DMARC alignment rather than just SPF. For example, Mailgun provides comprehensive guides.
• Verify SPF necessity: Always confirm whether an ESP's SPF include is truly needed for your domain, especially if they use a unique Return-Path subdomain for your sends. When setting up Mailchimp for example, SPF is generally not required on your root domain.
• Monitor DNS lookups: Use tools to check your SPF record's DNS lookup count to avoid exceeding the limit, which can lead to authentication failures and reduced inbox placement.
• Simplify explanations: Develop simplified explanations for clients about how email authentication works, focusing on the practical implications of proper setup rather than deep technical details.

Key opinions

• Documentation quality: SPF record documentation from ESPs is frequently criticized as being a 'train wreck' due to its inaccuracies and potential for misguidance.
• Strict lookup limit: The 10 DNS lookup limit for SPF records is a rigid standard that must be respected; exceeding it results in SPF failure, impacting deliverability.
• Historical context: Some legacy SPF recommendations were pragmatic, albeit temporary, solutions to specific deliverability challenges before more robust protocols like DKIM and DMARC were widely adopted.
• Modern authentication focus: The industry has moved towards more sophisticated authentication methods where SPF primarily validates the Return-Path, and DKIM/DMARC handle the visible From domain alignment.

Key considerations

• Adhere to RFCs: Always prioritize adherence to the official RFC standards for SPF, which clearly define the lookup limit and validation process. Ignoring this can lead to SPF TempError.
• Advocate for clarity: Experts should encourage ESPs to update their documentation to reflect current best practices and avoid recommending unnecessary SPF includes for primary domains.
• Focus on alignment: Guide senders to focus on proper DMARC alignment, which ensures both SPF and DKIM pass for the visible From domain, leading to better inbox placement.
• Continuous education: Continuously educate the email community on the evolving landscape of email authentication, emphasizing why some ESP recommendations are incorrect.

Key findings

• RFC compliance: RFC 7208 (the SPF specification) explicitly defines a maximum of 10 DNS lookups allowed when evaluating an SPF record.
• Domain validation: SPF validates the domain specified in the Mail From (envelope sender or Return-Path), which is distinct from the visible From header address.
• ESP subdomain usage: Many ESPs configure their systems to send emails using a subdomain of their own (or a user-specific subdomain) as the Return-Path, making an SPF record in the user's primary domain unnecessary for SPF pass.
• Simplified setup: Some ESPs, like AWeber, explicitly state that updating a user's domain's SPF record is not required for their service.

Key considerations

• DNS lookup management: Always ensure your SPF record adheres to the 10 DNS lookup limit. Exceeding this can lead to SPF PermError, preventing your emails from being authenticated correctly.
• Understand domain roles: Differentiate between the Mail From domain (for SPF) and the From header domain (for DKIM and DMARC alignment). This distinction is key to proper configuration and avoiding SPF TempError.
• Prioritize DMARC: Implement DMARC to enforce authentication policies and ensure both SPF and DKIM alignment, providing comprehensive protection against spoofing and phishing.
• Consult technical resources: When in doubt, always refer to authoritative technical documentation from organizations like the IETF or reputable email authentication guides to ensure correct implementation of SPF.