在邮件功能laravel 5中添加标头

I am updating code from laravel 4 to laravel 5

In laravel 4 there is mail functionality implemented with some code like below

Mail::send('emailtemplate.sample', $content_data, function ($message) use ($to_mail, $email_data, $from_name) {
            $message->from('admin@domain.com', 'admin')->to($to_mail)->subject($email_data->subject);                
            $headers = $message->getHeaders();
            $headers->addTextHeader('X-MC-PreserveRecipients', 'false');
        });

I don't know how to replace $headers = $message->getHeaders(); and $headers->addTextHeader('X-MC-PreserveRecipients', 'false'); in laravel 5 mail functionality

If anyone knows, then please suggest

As jszobody mentioned,

The getHeaders() method is being called on Swift_Message which isn't part of Laravel, it's a third-party component. So even though Laravel 5 has changed, Swift hasn't and should continue working like before.