External loader can fill a work queue with messages based on an external data source, e.g. by loading e-mails, files or data from web services.
Make sure these parameters are set in your AsapSettings.config file:
Set up the ExternalWorkQueueCheckPeriod to any number of seconds you want the files being checked.
BUILT-IN EXTERNAL LOADERS
Some of the loaders are built-in. You can create your own by using a universal Workflow Loader.