$mail           = new PHPMailer();
$mail->From     = "mailbox@domain.tld";
$mail->Mailer   = "mail";
$mail->CharSet  = "windows-1250"; //for example

$result = query("SELECT email FROM newsletter;");
while ($row = fetch_row($result))
{
  $mail->Body     = $text;
  $mail->Subject  = $subject;
  $mail->AddAddress($row[0]);

  if(!$mail->Send())
    echo "Error sending to " . $row[0] . "<br>";
  else
    echo "OK sending to " . $row[0] . "<br>";

  $mail->ClearAddresses();
}