// Get component configuration parameters as set into admin options (define in config.xml file)
 $content_params = JComponentHelper::getParams( 'com_bt_property' );

// Get specific parameter, here we are getting user groups set in admin of component options.
 $guest_usergroup = $content_params->get( 'guest_usergroup' );

// Import access for Joomla 3.x
jimport( 'joomla.access.access' );
 
// Loop through all groups set in admin option.
 foreach($guest_usergroup as $gu) {

// Get all users of that specific group
 $users = JAccess::getUsersByGroup($gu);
 foreach($users as $u) {
// Get single user of that specific group and add their mail into array.
 $user = JFactory::getUser($u);
 $recipient[] =$user->email;
 } 
 }
// Print out user groups set in options and recipent email array list.
 echo '<pre>';print_r($guest_usergroup);print_r($recipient);echo '</pre>';