Please check the location document of your address book. (the bottom right have shortcut)
If the basic --> internet email address is not your email address. It will probably cause the problem because the program use the location document to recognize "you".
If the internet email address is not correct, the program will assure you as one of recipient in the recipient list; and you are not the owner of your mailbox. Therefore when you reply all in the email, your email is appeared in the CC list.