That's when you start embarassing the person. A group of students included my email address in their project discussion. They ignored my emails asking to remo

That's when you start embarassing the person. A group of students included my email address in their project discussion. They ignored my emails asking to remove my address. So I started replying as if I was a part of their project, but requested/suggested slightly stupid things. They figured it out real fast after that. If you have the person's actual email, CC him on all that. If not, include a note saying your a different John Doe and to please remind the John Doe they want to reach, to use his own email address.