SMTP Path Analysis

Most proponents of domain authentication suggest combining domain authentication with reputation services. This paper presents a new learning algorithm for learning the reputation of email domains and IP addresses based on analyzing the paths used to transmit known spam and known good mail. The result is an effective algorithm providing the reputation information needed to combine with domain authentication to make filtering decisions. This algorithm achieves many of the benefits offered by domain-authentication systems, black-list services, and white-list services provide without any infrastructure costs or rollout requirements.