Put your email code inside your IF statement so it only sends after the form is posted. Currently it sends when the page loads and a second time when the form submits.
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.