hi thanks for the reply i do not want to install it globally but in a website (vhost) thats already added on ispconfig... is that possible, it should be only used by the client this site belongs to
You will have to integrate mailman in the mail system of your server, you can not install it in a vhost. If you search for some kind of mailing list program that can be installed into a vhost, have a lok at e.g. phplist.