Thanks for the quick answer.
We need not a whole groupeware! We are six persons who have to plan and handle a project for the next 12 moths. So we need a calendar-function that is able to be synchronize with Smartphone’s (e.g. the iPhone), a task manager, an email client (all members should have access to the mails) and a memo-function. This is necessary because all of us do this project in our spare time and we haven't the time to meet us periodical!
Maybe you know any other solutions that fit our problems!