Layered SPF Policy Structure for Nuanced Message Trust

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Solution Overview

Problem

Existing SPF policies are limited to binary pass/fail checks, which do not appropriately represent message trust levels, leading to issues with deliverability and security, especially in indirect message flows.

Innovation Solution

Implementing a layered SPF policy structure, with a top layer policy dividing addresses into categories and multiple second layer policies for identifying IP addresses corresponding to each category, allowing for more nuanced authorization results.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If binary pass/fail SPF policies are used, then policy simplicity is maintained, but message trust level representation is insufficient

Engineering Contradiction:

Improvepolicy structureVSAvoidmessage trust level

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent segments the single SPF policy into multiple layered policies (first layer, second layer, etc.). Each layer divides message sources into different categories with distinct trust levels. The first layer policy divides addresses into categories, and second layer policies identify specific IP addresses for each category, enabling nuanced authorization results that represent different confidence levels.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If layered SPF policies are implemented, then message trust level representation is improved, but policy complexity increases

Engineering Contradiction:

Improvemessage trust levelVSAvoidpolicy structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent adds a dimensional layering structure to SPF policies, organizing them hierarchically across multiple layers. The first layer policy operates at one dimension by dividing addresses into categories, while second layer policies operate at another dimension by identifying specific IP addresses for each category. This multi-dimensional approach enables precise trust level representation while structuring complexity in an organized, manageable hierarchy.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS12309204B2SPF layering for performant message authorization assertions

Publication Date: 2025.05.20 FRAUDMARC INC

AI summary

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. Embodiments of the present disclosure enable new SPF techniques such as creating a top layer SPF policy for dividing addresses into categories, and multiple second layer SPF policies for identifying IP addresses corresponding to each category. One of the second layer policies is selected as a default policy, such that any IP address that does not correspond to any other of the second layer SPF policies will match the default policy.