function is_valid_mailaddr($email)
{
  $a = "[a-zA-Z0-9_\-\.]";
  $w = "[a-zA-Z0-9]";
  $regex = "~^{$a}+@{$w}{$a}+\.{$w}{2,4}$~";
  
  if (preg_match($regex, $email) === 0) {
    return false;
  }
  
  $ignores = array(
    "bsnow.net", "mailinator.com", "mailexpire.com", "maileater.com",
    "jetable.org", "spambox.us", "guerrillamailblock.com", "tempomail.fr",
    "tempemail.net", "spamfree24.com", "spamfree24.eu", "spamfree24.net",
    "spamfree24.info", "spamfree24.de", "spamfree24.org", "spam.la",
    "supermailer.jp", "dea-gw.com", "renraku.in", "filzmail.com",
    "upken.jp", "mintemail.com", "meltmail.com", "dodgit.com", "mgne.jp",
    "spamcorptastic.com",
  );  
  
  foreach ($ignores as $ignore) {
    if ($ignore === substr($email, -strlen($ignore))) {
      return false;
    }   
  }
  
  list (, $domain) = explode("@", $email);
  if ($domain !== gethostbyname($domain)) {
    return true;
  }
  
  getmxrr($domain, $mxs);
  return !empty($mxs);
}