High Quality Content by WIKIPEDIA articles! Microsoft Office Communicator is a instant messaging client used with Microsoft Office Communications Server and is the replacement for Windows Messenger which was used with Exchange Messaging Server. Compared to Windows Live Messenger it has an expanded feature set that is targeted toward corporate environments. Basic features include instant messaging, Voice Over IP, and Video Conferencing inside the client software. Advanced features are related to integration with other Microsoft software: Availability of contacts is based on Microsoft Outlook calendars stored in a Microsoft Exchange Server.