Abstract: A solution for analyzing and filtering an email message destined to a computing resource in a computer network that has been security processed by a cloud-based email security system. The solution includes establishing a communication link with the cloud-based email security system, receiving an email message by an on-premises email security (OPES) system hosted in a demilitarized zone in the computer network, determining whether the received email message is sent from an authorized node in the cloud-based email security system, forwarding the received email message to an on-premises email security gateway located in the demilitarized zone, analyzing the forwarded email message, and sending the forwarded email message to a mail server in the computer network.