Laravel 5.0.33 Illuminate\Database\Eloquent\Model not found in line 5

Question

Here is my file Email.php in app, it is very simple but it doesn't work:

<?php
    namespace App;
    use Illuminate\Database\Eloquent\Model;

    class Email extends Model {
        protected $table = 'emails';
        public $timestamps = false;
    }
?>

Laravel 5.0.33 Illuminate\Database\Eloquent\Model not found in line 5