if (mail($to, $subject, $msg, "From: $email\r\nReply-To: $email\r\nReturn-Path: $email\r\n"))
bunu
if (mail($to, $subject, $msg, "From: ben@hazarkent.com.tr\r\nReply-To: $email\r\nReturn-Path: $email\r\n"))
Bu şekilde yapıp deneyebilirsin.