Microsoft have done changes in Exchange Server 2003 SP2. It includes new DLLs for several key APIs, and includes some key changes in behavior. While Exchange Server 2003 SP2 does not include any changes to the objects, classes, and interfaces, it does introduce key differences in how some of the APIs work.
The following API libraries that ship with Exchange Server 2003 or with Microsoft Outlook 2003 have been updated in Exchange Server 2003 SP2:
- Collaboration Data Objects for Exchange 2000 Server (CDOEX) CDOEX ships as part of Exchange Server 2003, and must be run on the computer running Exchange Server 2003. The version of CDOEX.DLL that contains this change is 6.5.7638.2.
- Collaboration Data Objects (CDO) version 1.2.1 CDO 1.2.1 is installed by Outlook 2003 and by Exchange Server 2003. CDO 1.2.1 is not redistributable, and must be run only on computers on which Outlook 2003 or Exchange Server 2003 is installed. The version of CDO.DLL that contains this change is 6.5.7638.2.
- Exchange OLE DB (ExOLEDB) Provider The ExOLEDB provider ships as part of Exchange Server 2003, and must be run on the computer running Exchange Server 2003. The version of the ExOLEDB provider DLL that contains this change is 6.5.7638.2.
Important:These changes only affect the libraries that ship with Exchange Server 2003. The libraries that ship with Microsoft Windows XP, Microsoft Windows 2000 Server, Microsoft Windows Server 2003, and Microsoft Exchange 2000 Server are not affected by these changes.
For more information, please find the detailed article available
Exchange Server, Service Pack, SP2, API, DLL, Microsoft
Source:? MSDN Blog