If your IP address has a bad reputation then speak to your ISP or change to a different provider. Find what your iP address and search using this http://www.projecthoneypot.org or this http://mxtoolbox.com/SuperTool.aspx# or google it to see what blacklists it features on and see what is required to get removed from them.
I manage a few websites and due to the abuse emanating from many countries I block entirely China, Russia, Ukraine, Romania, Turkey, Poland, Brazil to name but a few.