Patent attributes
Sender Policy Framework (SPF) is a widely used method of distinguishing authorized email from unauthorized email. SPF policies are published into a domain's DNS and then looked up and evaluated by mail receivers. Due to the complexity and limitations of the SPF specification, implementation mistakes and risks are widespread. This problem is compounded by the common practice of nesting SPF policies which introduces hidden risks, particularly exceeding DNS lookup limits. Embodiments of the present disclosure enable new SPF techniques such as selectively inactivating parts of a policy by introducing a virtual-all term, designed to secure against the third-party term inclusions in the policy. When the primary policy is online, the virtual-all term may serve as a terminate policy evaluation much like a traditional “all” term. If the primary policy is offline, a “fail open” may be produced, allowing policy evaluation to proceed into previously inactivated segment of the policy.
