مشکل در ارسال ایمیل

[Payam.Hayati 15]

سلام
قسمتی برای بازگرداندن پسورد کاربر از طریق ایمیل در سایت ایجاد کردم اما ایمیل ارسال نمی شود.
این کدها:

//receive user
 
if (isset($_POST['sub_receive_pass']) && !empty($_POST['txtEmail'])) {
 
 
 
    $email = htmlentities($_POST['txtEmail']);
 
    $safe_email = mysqli_real_escape_string($conn, $email);
 
 
 
 
 
    //search pass
 
    $sel_user = "select * from users where u_email = '$safe_email'";
 
 
 
    $run_user = mysqli_query($conn, $sel_user);
 
    $check_user = mysqli_num_rows($run_user);
 
    $main_email = "";
 
 
 
    if ($check_user > 0) {
 
        mysqli_set_charset($conn, "utf8");
 
        $sql = "SELECT * FROM users where u_email = '$safe_email'";
 
        $result = mysqli_query($conn, $sql);
 
        while ($row = mysqli_fetch_assoc($result)) {
 
            $main_email = $row["u_email"];
 
            $pass = $row["u_pass"];
 
 
 
            //send email
 
            $headers = "MIME-Version: 1.0" . "\r\n";
 
            $headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";
 
            // More headers
 
            $headers .= 'From: <[email protected]>' . "\r\n";
 
            $headers .= 'Cc: [email protected]' . "\r\n";
 
            $subject = "Password key";
 
            $descrip = "";
 
            //mail("payam.hayati@yahoo","$subject","$descrip","From : $email","$headers");
 
            mail("$main_email", "$subject", "$descrip", "Password : $pass", "$headers");
 
            echo "<script>alert('Password sent to your email')</script>";
 
            echo "<script>window.open('forget.php', '_self')</script>";
 
            return;
 
        }
 
    } else {
 
        echo "<script>alert('This email is not registered in the system!')</script>";
 
        echo "<script>window.open('forget.php', '_self')</script>";
 
    }
 
}
 
if (isset($_POST['sub_receive_pass']) && empty($_POST['txtEmail'])) {
 
    echo "<script>alert('Enter your email address')</script>";
 
    echo "<script>window.open('forget.php', '_self')</script>";
<span style="color: #333333;"><span style="font-size: x-small;"><span style="font-family: Tahoma, Helvetica, Arial, sans-serif;">} </span></span></span>