problem with codeigniter html mail

[eluser]LoRdCoStE[/eluser]
I have succesfully sent 3000 text mail with codeigniter mail class. (using BCC)
I have also sent about 5 html mail with codeigniter.

But something strange happen when I try to send an high numbers of html mail (3000).

Here the code:
config/email.php:

Code:

$config['bcc_batch_mode'] = TRUE;
$config['bcc_batch_size'] = 100;
$config['protocol'] = 'mail';
$config['wordwrap'] = FALSE;

$config['mailtype'] = 'html';

Code:

function send() {
        
        $this->load->model('mail_model', 'mail');
        
        $mails = array();
        
        foreach($this->mail->getMail() as $m) {
              if($this->_isValidMail($m['mail']))
             $mails[] = trim($m['mail']);
        }
        
        $this->load->library('email');
        
        $this->email->from('[email protected]', 'My mail');
        
        $this->email->to('');
        
        $this->email->bcc($mails);
        
        $this->email->subject('subject');
        
        $this->email->set_alt_message("Se non riesci a visualizzare questa mail visita:\n
        http://www.octima.it/newsletter/01.html");
        
        $this->email->message(file_get_contents('http://www.octima.it/newsletter/01.html'));
        
        if ( ! $this->email->send())
        {
            echo 'Error!!!<br />';
        }
        
        # debugging
        echo $this->email->print_debugger();

    }

The mails are sent but are unreadable full of strange code:

Code:

...
=3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D =3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D Modena Fiere. Un servizio creato per i professionisti=3D3D3D3D3D3D3D3D3D3D= 3D=3D 3D=3D3D 3D=3D3D3D 3D=3D3D3D3D 3D=3D3D3D3D3D 3D=3D3D3D3D3D3D 3D=3D3D3D3D3D3D3D 3D=3D3D3D3D3D3D3D3D 3D=3D3D3D3D3D3D3D3D3D 3D=3D3D3D3D3D3D3D3D3D3D 3D=3D3D3D3D3D3D3D3D3D3D3D 3D=3D3D3D3D3D3D3D3D3D3D3D3D 3D=3D3D3D3D3D3D3D3D3D3D3D3D3D
...