Thanks, but the real credit should go to the guys at http://sourceforge.net/projects/squirreloutlook/
since they have created the overall package. What I did was only a pkg file for easy installation of the software in ISPConfig.
I will most likely not continue the development of this since I don't use ISOConfig (yes, it's a good piece of software but was a bit overkill for my need).
I suggest that you keep an eye on the original project and when they releases a new version it should be quite easy to make a diff and create a new ISPConfig package.