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What Is an SPF Qualifier?

This article explains what an SPF qualifier is and what it does.

An SPF (Sender Policy Framework) qualifier is a prefix symbol added to an SPF mechanism that tells receiving mail servers what to do when a sending server matches that rule. Qualifiers control whether an email is accepted, flagged as suspicious, or rejected.

Common SPF Qualifiers

  • + Pass (default): The sender is authorized and the email passes SPF.

  • - Fail (Hard Fail): The sender is not authorized and the email should be rejected.

  • ~ SoftFail: The sender is likely unauthorized; the email is usually accepted but treated as suspicious and often sent to spam.

  • ? Neutral: No policy decision is made; the email neither passes nor fails SPF (generally not recommended).

How SPF Qualifiers Work

  • Mechanisms define who can send: SPF records list approved senders using mechanisms like include, a, or ip4.

  • Qualifiers define the action: Each mechanism may have a qualifier that tells receivers how to handle a match.

  • Top-down evaluation: Receiving servers evaluate SPF mechanisms in order and stop at the first match.

  • Default behavior: If no qualifier is specified, + (Pass) is assumed.

~all vs. -all

  • ~all (SoftFail): Commonly used during setup or monitoring to avoid rejecting legitimate mail.

  • -all (HardFail): Used once you’re confident all authorized senders are included and want strict enforcement.

Why SPF Qualifiers Matter

Qualifiers give mailbox providers clear guidance on how to treat unauthorized email, helping reduce spoofing while protecting legitimate delivery.