I am not a teacher, but I am a native speaker.
Do you want the people to know who else it was sent to, or only to know that you sent it to them? Also, is this an email, or a written/typed letter? If it is a typed letter, I am not sure exactly what you meant by "I want each person to receive an original letter, and not a copy".
NOTE: Also, you do not have to say "I am not a teacher" if you are asking a question. Only people who answer questions are required to do that, such as my post here.