Symfony Mailer base64 encoding

Question

How can we use the setEncoder() function that we used in the old swiftmailer library on the new Symfony mailer? I think setEncoder has been removed from symfony mailer. Every mail sent is automatically quoted-printable.

The transport and email I created normally work fine.

$transport = Symfony\Component\Mailer\Transport::fromDsn($env); 
$mailer = new Symfony\Component\Mailer\Mailer($transport); 

$message = (new Symfony\Component\Mime\Email());
$message->from("..");
...
$message->html('<p>Lorem ipsum</p>','utf-8');
$mailer->send($message);

But where should we use the base64 encoder value?

$encoder = new Symfony\Component\Mime\Encoder\Base64Encoder();