There is not currently a way to bounce an email address from Gmail itself. There are Email clients (Such as Apple Mail) that have that option. Be aware, if you bounce and email from someone who KNOWS that you still have the address, that will not prevent them necessarily from sending you more messages. It may even appear to be dishonest. A better solution would be to set up a filter with a 'canned response' that prevents you from seeing the message and lets the individual know that messages from them are unwelcome. Here are the steps:
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