if (db_num_rows($result)) {
  while ($row = db_fetch_object($result)) {
    $sql = ("SELECT * FROM {maildigest_mail} mm WHERE mm.uid = %d", $result->uid);
  $result = db_query($sql);
  while ($row = db_fetch_object($result)) {
    // group mails by user
    $allmail[$row->uid][] = $row;
  }
  foreach ($allmail as $uid => $mails) {
    // Send email
    set_time_limit(20);
    maildigest_send($mails, $uid);
  }

  }

}