How to get laravel transport mailer username with failover

[arnal1]

i have setup 2 smtp mailers:

'smtp' => [
     'transport' => 'smtp',
     'host' => smtp.gmail.org,
     'port' => env('MAIL_PORT', 587),
     'encryption' => env('MAIL_ENCRYPTION', 'tls'),
     'username' => 'smtp1@gmail.com',
     'password' => env('MAIL_PASSWORD'),
     'timeout' => null,
     'local_domain' => env('MAIL_EHLO_DOMAIN'),
],
'smtp-1' => [
     'transport' => 'smtp',
     'host' => smtp.gmail.org,
     'port' => env('MAIL_PORT', 587),
     'encryption' => env('MAIL_ENCRYPTION', 'tls'),
     'username' => 'smtp2@gmail.com',
     'password' => env('MAIL_PASSWORD'),
     'timeout' => null,
     'local_domain' => env('MAIL_EHLO_DOMAIN'),
],

and set failover:

'failover' => [
            'transport' => 'failover',
            'mailers' => [
                'smtp'   
                'smtp-1'
            ],
        ],

and send email as below:

$transport = $Mail::raw($message, function($msg) use ($to, $subject) {
            $msg->to($to)->subject($subject);
        });

the problem how can i get the actual sender transport mailer, since it can failed and swith to other mailer?

i expect to get either smtp1@gmail.com or smtp2@gmail.com.

i try to create macro to mailer class but failed since the transport variable set as private

Mailer::macro('getTransport', function () {
            return $this->transport;
        });