If you are trying to download the outlook plugin, and you get this error message:
You will need to download the VSTO (Visual Studio Tools for Office). This will do no harm to your machine and once this is downloaded, the CANDDi outlook will install normally and you will be able to use the plugin to its full effect.
Here is the link to download VSTO 4.0:
This is mainly for people using older Outlook i.e: 2011,2012 & 2013