We allow all of our clients to use their own domain for their marketplace. Once your marketplace is set up, all that you need to do is configure the DNS settings on the domain from where you purchased it, and point the web traffic (normally www) to our IP address that we supply.
We do not however provide email services. If you do not already have this provided to you, we highly recommend using Google Apps for Business. For a very small and affordable price, Google provides some amazing tools for your business. Additionally their inbuilt spam prevention tools are world class and should prevent you from receiving any unwanted email.