It definitely looks like the hosting server is at fault for the emails not sending. Have them check if they changed any settings that need to be set for emails to be sent.
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.