"describes a relatively straight-forward approach to an XML-RPC to POP3 gateway. The goal is to enable POP3 access to all environments supporting XML-RPC.
This API also introduces a (to the XML-RPC community) - as far as I know - new authentication system. An authentication call returns a session id (called SID) which is used to authenticate successive calls. Commonly this is done by providing a SID param with successive calls. The following API approaches this problem by providing the authenticated functions under a method namespace containing the SID and therefore only accessible to the authenticated client during one session."