Abstract: The software tool of the present invention operates on a network connected to plural messaging systems and is a synchronization engine to provide a unified messaging system. It consists of a series of intelligent logic functions and filters. The engine periodically polls the various messaging systems and is able to accept lists of messages from any messaging system (voice, e-mail, fax, or otherwise), correlate changes to the messages based on definable parameters (such as: size, date, type, status), and then replicate and synchronize the messages between all of the messaging systems in appropriate formats. By doing this, each messaging system can contain identical content using the most recent version so that any of the messaging systems can be accessed and the exact same data can be independently accessed and modified. The present invention's logic functions are optimized to eliminate copying of unchanged messages.