Multiple reminder email when you have a dev/test copy of your site

I bet many of you have multiple copies of your Drupal sites so that you may write new code or test new modules without mucking up your production site. How do you deal with Signup reminder emails on your non-production sites? Without modification, users would receive three copies of each signup.

I added this little bit of code at line 34 of includes/cron.inc to solve our problem, but I bet a better solution exists. Can you tell me?

global $base_url;
  if (!strstr($base_url, "www.catlin.edu")) {
    // Not the production Catlin Gabel website, so don't send reminders
    return;
  }