How do I stop certain emails from coming to me?

I have been receiving emails for the past few weeks stating that I have either won a lot of money or that I am a beneficiary and am receiving a lot of money from people that I have never heard of. I do not believe that they are legitimate, I have asked and demanded not to be contacted anymore but they still send them. I even received an email stating that they was the FBI, which I don't believe to be true either. I just want them to stop.