Description
In #33409 it's explained that you need to do this to select the transport to use to send the email message:

// use the first "main" transport
$mailer->send($email);

// or use the "important" one
$email->getHeaders()->addTextHeader('X-Transport', 'important');
$mailer->send($email);

That doesn't look very user friendly 😐 Could we make it easier to use? Maybe like using multiple SwiftMailer mailers in Symfony apps? (Maybe that's already the case and we just need to document it?) Or maybe add another argument to send() method or add another method to select the transport?