Peter, I've sent you a PM with all my information.
Peter, I tried sending you another email and still getting the same message,
"delivery has failed to these recipients or groups: the email address you entered could not be found". It seems like it's an issue with your SMTP server that is part of your website. I'd contact whoever setup the website or the company that hosts it and ask for their advice on what's going on. I could be mistaken but I don't think that's an issue with your computer but rather it's an issue with your Server.