nono ... lo script non riparte ^^ ... riparte semplicemente il ciclo 
codice:
$counter = 0;
$bcc_addresses = array();
while(list(, $email) = each($addresses))
{
$bcc_addresses[] = $email;
$counter++;
if ($counter == 51)
{
$destinatario = array_shift($bcc_addresses);
$bcc_addresses_string = implode(", ", $bcc_addresses);
mail($destinatario, $soggetto, $body, $headers . "Bcc: " . $bcc_addresses_string);
$counter = 0;
$bcc_addresses = array();
}
}
if ($counter > 0)
{
$destinatario = array_shift($bcc_addresses);
$bcc_addresses_string = implode(", ", $bcc_addresses);
mail($destinatario, $soggetto, $body, $headers . "Bcc: " . $bcc_addresses_string);
$counter = 0;
$bcc_addresses = array();
}