An anti-spam method via real-time retransmission detection

Tempfailing is widely used in many organizations as anti-spam technology. However, this technology causes a serious problem: it imposes long delays in mail delivery. To solve this problem, another technique called 5-Way Handshake was proposed, but its conventional implementation has a serious drawback. Based on the MX fallback mechanism defined by RFC5321, a legitimate sender must access MX hosts in order of their preferences. By making communication between primary and secondary MXs, the method examines whether a mail delivery follows the mechanism. This causes heavy communication overhead. In this paper, therefore, we propose modified mechanism of 5-Way Handshake for an anti-spam system in order to detect MX fallback in real-time.