Symfony version(s) affected: 4.3.3

Description

Method Symfony\Component\Mailer\Transport\AbstractTransport::send, implementation of Symfony\Component\Mailer\MailerInterface::send(RawMessage $message, SmtpEnvelope $envelope = null) accepts Symfony\Component\Mime\RawMessage, but by default (when $envelope is null) creates Symfony\Component\Mailer\DelayedSmtpEnvelope, which accepts Symfony\Component\Mime\Message. So when I use a smtp transport, I cannot call Symfony\Component\Mailer\MailerInterface::send() with a RawMessage even though the type seems to allow it.

How to reproduce

/**
 * @var MailerInterface
 */
private $mailer;

method() {
    $this->mailer->send(new RawMessage('content'));   // Argument 1 passed to Symfony\Component\Mailer\DelayedSmtpEnvelope::__construct() must be an instance of Symfony\Component\Mime\Message, instance of Symfony\Component\Mime\RawMessage given, called in /var/php/prod/vendor/symfony/mailer/Transport/AbstractTransport.php on line 66
}

Possible Solution

Additional context