CDO (Collaboration Data Objects)

An Application Programming Interface that is a superset of CDO for Windows 2000. In addition to gaining programmatic access to the Simple Mail Transfer Protocol (SMTP) and Network News Transfer Protocol (NNTP) stacks, CDO for Exchange 2000 provides support for the creation and manipulation of message items, appointments, and contact cards. [Exchange 2000]

An application programming interface (API) that enables users and applications to have high-level access to data objects within Exchange. CDO defines the concept of different object classes, including messages, posts, appointments, and tasks. [Exchange 2003]