update

app/Http/Controllers/Admin/MailController.php

@@ -11,7 +11,7 @@ use App\Jobs\SendEmail;
 class MailController extends Controller
 {
     public function send (MailSend $request) {
-        if ($request->input('type') == 2 && $request->input('receiver')) {
+        if ($request->input('type') == 2 && empty($request->input('receiver'))) {
             abort(500, '收件人不能为空');
         }