Quick and dirty php command line script to check a list of domains for those that use gmail. For email nerds, fanboys and geniuses only.

googlecheck.php

#!/usr/bin/php
<?php
/**
 * Checks a list of domains and outputs any that use Google.
 *
 *  usage:  php ./googlecheck.php filewithdomains
 *
 */

stream_set_blocking(STDIN, 0);

if (count($argv)<2)
{
    echo "usage: googlecheck.php [filename]\n";
    exit;
}
$domains = $argv[1];
if (!file_exists($domains))
{
    echo "\n'$domains' is not a valid file\nusage: googlecheck.php [filename]\n";
    exit;
}
$trimmed = file($domains, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
if (!is_array($trimmed))
{
    echo "\nFile does not contain list of domains.\nusage:  ./googlecheck [filename]\n";
    exit;
}
$domains_to_check = count($trimmed);
echo "\nChecking ".$domains_to_check." domains for gmail...\n\n";
checkGoogleArray($trimmed);
exit;
function win_getmxrr($hostname, &$mxhosts, &$mxweight=false) {
    if (strtoupper(substr(PHP_OS, 0, 3)) != 'WIN') return;
    if (!is_array ($mxhosts) ) $mxhosts = array();
    if (empty($hostname)) return;
    $exec='nslookup -type=MX '.escapeshellarg($hostname);
    @exec($exec, $output);
    if (empty($output)) return;
    $i=-1;
    foreach ($output as $line) {
        $i++;
        if (preg_match("/^$hostname\tMX preference = ([0-9]+), mail exchanger = (.+)$/i", $line, $parts)) {
          $mxweight[$i] = trim($parts[1]);
          $mxhosts[$i] = trim($parts[2]);
      }
      if (preg_match('/responsible mail addr = (.+)$/i', $line, $parts)) {
          $mxweight[$i] = $i;
          $mxhosts[$i] = trim($parts[1]);
      }
  }
  return ($i!=-1);
}
if (!function_exists('getmxrr')) {
    function getmxrr($hostname, &$mxhosts, &$mxweight=false) {
        return win_getmxrr($hostname, $mxhosts, $mxweight);
    }
}

function checkGoogle($array)
{
        foreach ($array as $str)
        {
           if (preg_match ('/(google|psmtp.com)/i', $str, $m))
           {
            return true;
          }
        }
    return false;
}


function checkGoogleArray($array)
{
    foreach ($array as $domain)
    {
       getmxrr($domain,$mxhosts,$mxweight);
       if (checkGoogle($mxhosts)==true)
       {
        echo "$domain\n";
    }
    else
    {
    }
}
}