Mass mailing - PHPMailer

Good morning!

I have an email marketing system and I'm having trouble making a newsletter shot for a large list of contacts. (Understand large list as: a list containing over 1000 emails.)

If I take the shot for less than 1000 emails, shooting happens perfectly. If there are more than 1000, it does not send for everyone, even sending up to half the list.

I contacted Localweb, the server that hosts my accounts and where I authenticated SMTP, and they informed me that it could be a possible loss of packages during the sending.

My code looks in the database (SQL Server) within a for loop for all mail from the list that has been selected for the trigger and then sends it there. One consideration: sending is performed by a Cron Job that runs every 5 minutes.

Can anyone help me? Any idea what that might be?

My shipping code:

    $mail = new PHPMailer();
    $mail->setLanguage('br');
    $mail->CharSet='utf-8';   
    $mail->IsSMTP(); 
    $mail->Host = "xxx";
    $mail->SMTPAuth = true;
    $mail->Username = 'xxx';
    $mail->Password = 'xxx';
    $mail->SMTPSecure = 'tls'; 
    $mail->Port = 587; 
    $mail->From = $email; (variável que vem do banco de dados)
    $mail->FromName = $fantasia; (variável que vem do banco de dados)
    $mail->SMTPOptions = array(
        'ssl' => array(
            'verify_peer' => false,
            'verify_peer_name' => false,
            'allow_self_signed' => true
        )
    );

    for($z=0; $z<count($bcc); $z++){

        if($html == '1'){
            $topo = recebe um código html específico;
              $rodape = recebe um código html específico;
              $texto2 = recebe um código html específico, concatenando as variáveis $topo e $rodape - newsletter que será enviada; 
        }else{
            if($topo == '1'){
              $topo = recebe um código html específico;
              $rodape = recebe um código html específico;
            }else{
                $topo = recebe um código html específico;
              $rodape = recebe um código html específico;
            }

            $texto2 = recebe o código html específico, concatenando $topo e $rodape - newsletter que será enviada; 
        }

        $mail->AddAddress($bcc[$z]['Email']);
        $mail->IsHTML(true);
        $mail->Subject  = $tit; (variável vinda do banco)
        $mail->Body = $texto2;
        $mail->AltBody = $texto2;
        $enviado = $mail->Send();
        $mail->ClearAllRecipients();
        $mail->ClearAttachments();

    }