Laravel Mail - InvalidArgumentException with message 'No connector for []'

I'm on Laravel 5.1, I configured my mail as described here https://laravel.com/docs/5.1/mail, and every config (config/mail.php, config/services.php) appears when I test from tinker. (eg: config('mail.driver'), etc)

But when I ran this from tinker

use Mail;Mail::raw('Test mail from Tinker', function($msg) {$msg->to('my-mail@gmail.com')->subject('Test Email'); });

I got this one single line exception

InvalidArgumentException with message 'No connector for []'

Any idea what could be the issue ?