Q: CDO? What's that? What "client app" uses that? How do I know if it needs to be updated?
A: CDO is "Collaboration Data Objects". CDO is an object model that developers can use in their custom solutions to do things like programmatically read or send email (via outlook) or access you address book. 3rd party software that directly interfaces with outlook on your workstation might use CDO, but outside that, it'd be rare. Microsoft doesn't have a "list" of 3rd party apps that might use CDO, but check out our partial general vendor list at http://support.microsoft.com/gp/dst_topissues#A6a. For general information on CDO, please see http://msdn.microsoft.com/msdnmag/issues/0600/cdo/.