How send subject using PHPMailer

Question

I use PHPMailer class. I've written a test email like this:

$mail = new PHPMailer();
$mail->SMTPDebug  = 2;   
$mail->Username   = "username"; 
$mail->Password   = "aaa";  
$mail->SetFrom('mail', 'name');
$mail->AddReplyTo("mail","name");
$mail->Subject    = "PHPMailer Test Subject via smtp, basic with authentication";
$mail->MsgHTML('BODYYY OF MESSAGE');
$address = "address";
$mail->AddAddress($address, "name");
$mail->addCC("mail", "name");
$mail->AddAttachment("a.jpg");      // attachment
$mail->Send();

Everything is all right, but it don't appended subject to header, i see code it appended only when called DKIM_add function. How can i send Subject without DKIM_add function?