I don't know, if anybody else ran into this very annoying issue? But I found out that when you add a new mailinglist, the /var/lib/mailman/data/virtual-mailman isn't postmapped. You have to do this by hand? This seems like a bug to me, but I am unsure if this is ISPConfig related? So, let me know, if you have the same issue with mailman, on Ubuntu 13.10, with the latest ISPConfig and mailman 2.1.16-rc2?