There are a couple of possibilities including a rule in your email program that could be duplicating the email. If you post the full email headers of the copy that you receive we can help you figure out where to look to solve the problem.
I have contacted the recipient at charter.net whom the email was sent too. I have also contacted the recipient to whom it was forwarded too(AOL). Charter.net recipient was not aware that the email was forwarded to recipients at aol and msn addresses. It was sent specifically to charter.net. Does that shed some light on what is happening.