WhiteHouse.gov Releases Open Source Code(whitehouse.gov)

  // the user may have put in an address of the form "Full Name" <[email protected]> instead of just the address,
  // so we want to filter to the right address
  function govdelivery_filter_email($address) {
    
    // borrowed from the drupal valid_email_address($mail) function
    $user = '[a-zA-Z0-9_\-\.\+\^!#\$%&*+\/\=\?\`\|\{\}~\']+';
    $domain = '(?:(?:[a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.?)+';
    $ipv4 = '[0-9]{1,3}(\.[0-9]{1,3}){3}';
    $ipv6 = '[0-9a-fA-F]{1,4}(\:[0-9a-fA-F]{1,4}){7}';
    
    // setup an array for the matching expression
    $matches = array();
    
    // the regex below is adapted from drupal's valid_email_address($mail) function
    preg_match("/$user@($domain|(\[($ipv4|$ipv6)\]))/", $address, $matches);
    return $matches[0];
  }