Message gateway with hybrid proxy/store-and-forward logic

Abstract

Described is a technology by which an email filtering service or other gateway includes hybrid proxy and store-and-forward logic. A message is initially processed with proxy logic. If the proxy logic is unable to complete filtering/scanning of a message within a timeout period, the store-and-forward logic is invoked to complete filtering/scanning of the message. The store-and-forward logic also may be invoked if a delivery attempt made by the proxy logic fails or does not complete prior to a delivery timeout period. When such a condition is met, the store-and-forward logic accepts the message, including storing the message, sending a response that indicates the message was accepted, and closing the connection over which the message was received. The store-and-forward logic may complete any scanning if not completed by the proxy logic, and takes over delivery responsibilities.