If you're going to run cron.php very often, you'll need to set up a separate cron job for bounce processing.
To do that, edit the admin/cron/cron.php file and comment out the 'bounce.php' line:
# require($mydir . '/bounce.php');
and set up a separate cron job to run 'admin/cron/bounce.php' once an hour (or even once every 2-4 hours, doesn't matter).
This is to reduce the load on your mail server by not checking for bounces every time that you send email campaigns or autoresponders.
Please NOTE that this method is intended for SendStudio older than 1.3... In the newer version, you can simply create one CRON entry, and specify the interval of "Send", "Autoresponder", and "Bounce Processing" separately in your SendStudio "Settings" page.
