I cannot set Message-ID and add multiple PDF with loop

i have tried to set message-id with this code

use Laminas\Mail\Message;
use Laminas\Mime\Message as MimeMessage;
$message = new Message();


$message->getHeaders()->addHeaderLine(‘Message-ID’, ‘generate.random@mydomain.com’);

and i got this message raw from my email
Message-ID: 5e88a6d1.1c69fb81.2faa8.789fSMTPIN_ADDED_BROKEN@mx.google.com

also how to set encoding to letter body without make it to setPart of MIME ?
and i cannot add multiple PDF attachments with loop

sorry my english seems like bad