send email to notify customer about china bankslip and instruction to upload po

app/Notifications/UploadPo.php

@@ -32,6 +32,7 @@ class UploadPo extends Notification
     public function toMail($notifiable)
     {
         $message = new MailMessage;
+        $message->subject('Upload PO - Exchange');
         $message->line('您好, 订单号 : '.$this->booking->id.' 的人民币汇款已成功。 请在这个网址 http://exchange.cief-malaysia.com/ 登录您的账号，并点击以下按钮，上载PO到系统. 谢谢.')
             ->line('The payment to your supplier for the order no: '.$this->booking->id.' has been successful, please login to your account at http://exchange.cief-malaysia.com/ and then click on the button below upload your order\'s po');
 //        foreach ($this->booking->chinaBankSlip as $bankslip){

routes/web.php

@@ -17,13 +17,6 @@ Route::get('/', 'WelcomeController@index');
 Route::get('password/reset/{token}', 'Auth\ResetPasswordController@showResetForm')->name('password.request');
 Route::post('password/reset', 'Auth\ResetPasswordController@postReset')->name('password.reset');
 
-Route::get('mail', function () {
-    $booking = \App\Booking::find(9323);
-
-    return (new App\Notifications\UploadPo($booking))
-        ->toMail($booking->user);
-});
-
 Route::get('/po-approval', function(){
     $approvedInvoices = InvoiceStatuses::where(function($q) {
         $q->where('status', 'approve')