A system and method for broadcasting data in the form of instant messages over a computer network. The broadcast system 100 preferably includes a messaging manager 200, an integration engine 300, a subscription manager 400, a scheduler 500, and a broadcast engine 600. The messaging manager 200 interfaces with all other components and provides a multi-threaded, run-time engine that coordinates the integration, triggering, scheduling, and message delivery activities for scalable broadcast applications. The integration engine 300 provides a system for “exposing” Web services and “consuming” external data streams. The subscription manager 400 includes an event watcher, which monitors the state of the external environment it interacts with, and an event dispatcher, which collects event subscriptions and ensures the instant delivery of events to all subscribers by way of the broadcast engine. The scheduler 500 allows users to customize the system 100 in order to schedule outgoing messages through the broadcast engine. The broadcast engine 600 enhances the inherent limitations of current IM technology by providing a multi-threaded broadcasting engine capable of sending volumes of messages from one server to literally thousands of IM clients concurrently over different private and public networks in one-to-one, one-to-many and many-to-many formats.