Can a sender modify SPF records to alter SPF checking behavior?
Summary
What email marketers say8Marketer opinions
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.
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.
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.
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.
Email marketer from SendGrid shares that SPF authentication process happens on the receiver's end, meaning senders cannot change that process by modifying records.
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.
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.
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.
What the experts say3Expert opinions
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.
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.
Expert from Email Geeks states that a sender cannot publish a record that will make the checking behavior different.
What the documentation says4Technical articles
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.
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.
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.
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.