Is a private email protected? How?

Copyright, a form of intellectual property law, protects original works of authorship including literary, dramatic, musical, and artistic works, such as poetry, novels, movies, songs, computer software, and architecture. Copyright does not protect facts, ideas, systems, or methods of operation, although it may protect the way these things are expressed. An e-mail might or might not qualify for copyright protection - it would depend on the content. Go see a copyright lawyer to find out.

While your e-mail may fall under copyright law (it depends upon the content), the actual issue here is whether you had any valid reason to believe the other person would keep your comments private. While you told the recipient that you wanted the information to stay just between the two of you, he or she didn't feel bound by your request. You can contact all the other recipients of the e-mail and ask that they not forward it to anyone. But your comments are already beyond your reach and you can't take them back. In the future, don't send anything out that you don't want the world to know.