What is known as Common Messaging Calls or CMC?  

Common Messaging Calls (CMC) is a library of 10 functions for adding simple messaging capabilities to client applications written in C or C++. CMC is built on top of the core MAPI subsystem so it shares the advantage of messaging system independence. The CMC API is especially valuable because it is also independent of the operating system, therefore useful for cross-platform client applications. CMC also includes support for the X.400 API.

The CMC supports three principal tasks:

Sending messages
Retrieving messages
Looking up addressing information


  • Current versions of the MAPI subsystem do not implement CMC.
  • Do not use CMC to implement messaging solutions.
  • Common Messaging Calls (CMC) is not installed by Exchange Server 2003 or later.
  • However, CMC is supported for use with Exchange 2003.
  • To function properly, the underlying Exchange or Microsoft Outlook® MAPI subsystem must be properly installed on the client computer.