Hi Albrecht,

you can divide your clients based on criteria like e.g.
-from where they came? In our department team we have created lists of people who had attended our webinars, download ebooks or signed up for newsletter,
-how far in the pipeline they are? you can use our lead and opportunity ready-to-use lists,
-if they are single contacts or companies?- more about it you can read here: http://help.instream.io/help/description-of-relations-lists/

What I can suggest is to add person to InStream ones he or she will reply to your email or answer your call to do not keep in our system people who has nothing to do with your business 😉

Hope it helps