Hi, thank you for your reply. I have to admit that I am not a linux mailserver guy. The minimal I excpected was that I am able to communicate within the same subnet when I install ootb. Sorry this is very discourageing for a integrated groupware solution and makes the decision difficult to evaluate longer. It leads rather to look for other solutions.
Ok, where I have to look why the webclient and any installed mailbox system (regardless of the used port) are not communication with each other?