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Can a sender modify SPF records to alter SPF checking behavior?

8 Marketer opinions3 Expert opinions4 Technical articles3 Resources

Summary

The overwhelming consensus from experts, documentation, and email marketers is that while senders have control over the content of their SPF records, they cannot modify SPF records to fundamentally alter the way SPF checking behavior is implemented by receiving mail servers. The logic for SPF verification resides on the receiving server and is dictated by the SPF specification (RFC 7208). Senders can add or remove authorized sending sources and optimize SPF records, but they cannot introduce custom commands, change how existing mechanisms work, or redefine the rules by which SPF is evaluated. Attempting to do so would undermine SPF's security purpose and lead to deliverability issues.

Key findings

  • Control Over Record Content, Not Behavior: Senders can manage the content of their SPF records (add/remove sources), but not the underlying SPF checking behavior.
  • SPF Specification (RFC 7208) Governs: SPF operates according to a defined specification, and proprietary extensions or commands are not allowed.
  • Receiver-Side Validation Predominant: SPF authentication happens on the receiving server, giving senders limited influence.
  • No Custom Logic Permitted: Introducing custom commands or logic to fundamentally alter SPF processing is impossible.
  • Security is Paramount: Changing SPF behavior would compromise its security and lead to email deliverability problems.

Key considerations

  • Focus on Proper Configuration: Ensure SPF records are configured correctly according to the specification to authorize legitimate sending sources.
  • Adherence to Standards is Mandatory: Comply with defined SPF standards; avoid deviations that cause errors and undermine security.
  • Understanding Limitations Critical: Acknowledge that senders can manage records but not control the overall SPF validation logic on the receiving end.
  • Optimizations Only for Efficiency: Optimize for efficient lookups and staying within limits, not for changing protocol operations.
  • Misunderstanding Leads to Issues: Misunderstanding SPF records is a common deliverability issue; proper knowledge is crucial.

What email marketers say
8Marketer opinions

The consensus is that while senders have control over their own SPF records, they cannot alter the fundamental behavior of SPF checking. Senders can add or remove authorized sending sources, optimize their records to stay within lookup limits, and correctly configure their records according to existing specifications. However, SPF behavior is ultimately dictated by receiving servers and the standards they adhere to, so senders cannot unilaterally change how SPF is interpreted or invent new SPF mechanisms.

Key opinions

  • Control over Record Content: Senders can manage the content of their SPF records, adding or removing authorized sources.
  • No Protocol Change: Senders cannot change the underlying way SPF works or invent new SPF mechanisms.
  • Receiver-Side Validation: SPF authentication happens on the receiver's end, preventing senders from altering the process.
  • Limited Customization: Customization is limited to existing SPF mechanisms, not introducing new functions.
  • Optimization for Limits: Senders can optimize records to stay within lookup limits, focusing on efficiency.

Key considerations

  • Correct Configuration: Focus on correctly configuring SPF records according to existing specifications.
  • Avoid Misunderstanding: Misunderstanding SPF records is a common cause of deliverability issues; proper understanding is essential.
  • Coordination is Impossible: Changing SPF behavior would require coordination across all email providers, which is practically impossible.
  • Impact on Deliverability: Incorrect SPF setup will have detrimental effects on email deliverability.
  • Compliance is Key: Abide by the SPF standard and keep records updated to avoid deliverability problems.
Marketer view

Email marketer from Mailjet responds that Senders should focus on correctly configuring SPF records according to the existing specifications, rather than attempting to alter how the system functions.

October 2024 - Mailjet
Marketer view

Email marketer from EmailGeek Forum shares that you are limited to using the defined SPF mechanisms (a, mx, ip4, ip6, include, etc.). You cannot add new functions or change how existing ones work.

December 2024 - EmailGeek Forum
Marketer view

Email marketer from EmailonAcid shares that misunderstanding SPF records is a common cause of deliverability issues. Changing SPF behavior would require coordination across all email providers.

June 2024 - EmailonAcid
Marketer view

Email marketer from Stack Overflow shares that while you can modify your SPF record to add or remove authorized sending sources, you can't change the underlying way SPF works. You can't invent new SPF mechanisms.

April 2024 - Stack Overflow
Marketer view

Email marketer from SendGrid shares that SPF authentication process happens on the receiver's end, meaning senders cannot change that process by modifying records.

July 2021 - SendGrid
Marketer view

Email marketer from Reddit responds that SPF behavior is dictated by receiving servers and the standards they adhere to. Senders can't unilaterally change how SPF is interpreted.

January 2023 - Reddit
Marketer view

Email marketer from Postmark explains that while senders can control the content of their SPF record, they can't redefine the rules by which it's evaluated, as that depends on the receiving mail server.

August 2021 - Postmark
Marketer view

Email marketer from Mailhardener explains while you can't change how SPF functions, you *can* optimize your SPF record to stay within the lookup limits. This is about efficiency, not changing the protocol.

March 2023 - Mailhardener

What the experts say
3Expert opinions

The consensus from experts is that senders cannot modify SPF records to alter the fundamental SPF checking behavior implemented by receiving servers. This is because the logic of SPF verification resides on the receiving end and adheres to a defined specification. Attempting to change SPF behavior through record modification would undermine its security purpose.

Key opinions

  • Immutability of SPF Logic: Senders cannot change how receiving servers interpret SPF records.
  • Receiver-Side Control: The logic for SPF verification is controlled by the receiving server.
  • Security Implications: Modifying SPF records to alter checking behavior would compromise security.

Key considerations

  • Focus on Correct Setup: Senders should focus on correctly configuring SPF records according to the defined specification.
  • Adherence to Standards: Compliance with SPF standards is crucial for proper email authentication.
  • Understanding Limitations: Recognize that senders can manage their SPF records but not control SPF verification logic on the receiving end.
Expert view

Expert from Word to the Wise shares that while senders manage their own SPF records, they can't control the logic of SPF verification on receiving servers. The specification dictates behavior.

October 2024 - Word to the Wise
Expert view

Expert from Spam Resource explains that SPF is a security measure, and senders cannot simply modify records to change how SPF is interpreted by recipient servers. Doing so would undermine the purpose of SPF.

September 2024 - Spam Resource
Expert view

Expert from Email Geeks states that a sender cannot publish a record that will make the checking behavior different.

September 2022 - Email Geeks

What the documentation says
4Technical articles

According to the documentation, senders cannot modify SPF records to fundamentally alter SPF checking behavior. The SPF protocol has a defined syntax and processing rules (RFC 7208), and deviations from this specification or attempts to introduce custom commands will lead to errors. SPF operates by verifying the sending server's IP address against authorized sources, a process that cannot be changed by the sender.

Key findings

  • SPF Protocol Defined: SPF functions according to a defined protocol.
  • No Custom Commands: You cannot introduce custom commands or logic into an SPF record to change how it's processed.
  • RFC 7208 Compliance: The SPF specification (RFC 7208) dictates the syntax and processing rules.
  • IP-Based Verification: SPF is checked against the sending server's IP address to verify authorization.

Key considerations

  • Adherence to Standards: Comply with the defined SPF protocol and avoid deviations that cause errors.
  • Focus on Correct Configuration: Ensure SPF records are correctly configured to authorize legitimate sending sources.
  • Understanding Limitations: Acknowledge that senders cannot alter the fundamental SPF checking process.
Technical article

Documentation from dmarcian explains that you cannot introduce custom commands or logic into an SPF record that would fundamentally alter how SPF is processed. The SPF record has a defined syntax, and deviations will lead to errors.

May 2021 - dmarcian
Technical article

Documentation from Microsoft explains that SPF is checked against the sending server's IP address to verify if it's authorized to send emails on behalf of the domain. You can't alter this process.

November 2021 - Microsoft
Technical article

Documentation from Valimail explains that SPF records cannot be altered by senders to change the fundamental behavior of SPF checking mechanisms as implemented by receiving mail servers. SPF functions according to a defined protocol.

January 2022 - Valimail
Technical article

Documentation from RFC 7208 (the SPF specification) explains that the specification dictates the syntax and processing rules for SPF records. Senders cannot introduce proprietary extensions or commands to change the behavior of SPF validation.

July 2022 - RFC Editor

Related resources
3Resources

SPF Softfail vs Hardfail - Valimail
SPF Softfail vs Hardfail - Valimail

Sender Policy Framework (SPF) is an email authentication method that uses the DNS to authorize which IPs can send mail on behalf of your domain. The syntax of SPF allows admins to define two kinds of failure scenarios for dealing with unauthorized mail: softfail and hardfail. Although the latter is formally just called a fail

Valimail -
SPF Record Check | SPF Checker | Mimecast
SPF Record Check | SPF Checker | Mimecast

Checking SPF records is vital for email security. Use our free online SPF Record Checker to lookup, check, and validate your SPF Records.

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SPF Failure: Typical Errors & How to Fix Them - Valimail
SPF Failure: Typical Errors & How to Fix Them - Valimail

Learn about classic SPF failures and what you can do to fix them. We'll cover all the best practices to help you avoid SPF issues & get to safer sending faster.

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