Universal Email version 4 will not work in DW version 8 . it is only compatible with DW Cs3 and above.
you will need to upgrade your Dreamweaver version to use version 4 of Universal Email.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.