An integrated messaging system uses existing messaging equipment to receive, store, retrieve and manage messages in media types and formats appropriate to each existing system using protocols which are specific to that system. Two or more systems are tightly coupled in that a message received in one system can be accessed from all systems. Coordination between messaging systems is achieved by a synchronizer system which periodically connects to each system by means of a standard interface and insures that messages created or received in one system are distributed or identified in all other messaging systems. Thus, the messaging systems can operate together even though they have different user interfaces, storage designs and formats and access and routing protocols. In one embodiment, a message received in one system is copied to the other system. In another embodiment, the header information in a message is preserved in a message created in the other system, but the message is not copied. The header information allows the message to be located and reproduced. In still another embodiment, one messaging system is designated as the single store for all messages.