User A send an email to user B. On user B, there exists a mail rule "send Full copy to user A". User A will receive the email send to user B.
By design, who ever sends an email to a user where in a mail rule of send full copy to exists, the listed user/s stated on the rule will receive the mails regardless if it is the same user.
Customer would not want for the user to receive the mail he/she has sent.