It is used by the RemoteDelivery Mailet to store mail for futher delivery. This is the parent node for all mailet configurations. The rootpath specify where mailet repository is. This is James sitemap. It defines how each incoming mail will be processed.
Incoming mails begins their process at the first mailet in the pipe.
The matching mail will be passed to the specified mailet for processing. After processing both mails, the untoched not matching and the processed matching, goes to next step in pipe. Some mailet will not return anything after process. The Null mailet for example will simply destroy any incoming mail or the RemoteDelivery since after delivery the mail needs no more processing. The Match interface defines how match class should work.