note 11897 added to ref.mail.php

I am getting an error from my users. They continaully receive my "registration verification" email when it has only been sent once using the PHP code below. Any ideas why they continue to receive this email everytime the hit send/receive??? Please help... send mail to john@unitymarketing.com. Thank You! mail($their_email, $subject, $message, "From: $send_name <\"$send_email\">\nReply-To: $send_email"); http://www.php.net/manual/it/ref.mail.php