A better private messaging system

One annoying thing is, sometimes I want to contact members privately. I don't want to post my e-mail address, and I don't want them to post theres since that is kind of unsafe. Is there a way for you to add the function of send a private message to poster or even a private e-mail to the person who posted a thread or reply? I can point out a few forums that do this very well, I just don't know if you can make it work with the system you are using for your forum.