Laravel 5.2 和代客 - 无法发送电子邮件 - 找不到套接字传输“普通”

我正在使用Laravel Valet和Laravel 5.2。当我尝试触发发送电子邮件时，我收到此错误：

Swift_TransportException in StreamBuffer.php line 269:
Connection could not be established with host mailtrap.io 
[Unable to find the socket transport "plain" - did you forget to enable 
it when you configured PHP? #1]

.环境文件：

MAIL_DRIVER=smtp
MAIL_HOST=mailtrap.io
MAIL_PORT=2525
MAIL_USERNAME=whatTheyGaveMe
MAIL_PASSWORD=whatTheyGaveMe
MAIL_ENCRYPTION=PLAIN

邮件功能：

public function sendClinicEmail($id, $emailType, $data)
{
    $user = User::findOrFail($id);
    Mail::queue('emails.clinic.' . $emailType . '', ['user' => $user, 'data' => $data], 
        function ($m) use ($user, $data) {
        $brandName = Config::get('brand.name');
        $m->from('hello@app.com', '' . $brandName . '');
        $m->to($user->email, $user->name)->subject($data['subject']);
    });
}

请问我该如何解决这个问题？无论我使用哪种类型的 AUTH，它仍然返回相同的错误，只是与 AUTH 类型有关。非常感谢。