The traditional asynchronous messaging systems (e-mail systems etc.) lack many advanced features, e.g. intelligence, controllability, scalability etc. to accomplish effective and sophisticated message handling. To supplement these features, we propose a Flexible Asynchronous Messaging System (FAMES). FAMES consists of autonomous and collaborative software agents. The messaging functions are composed of an organization of agents, and enhanced messaging services which are provided through cooperative behavior of message flow control agents. The authors focus on the Communication Mechanism of Loose Coupled Agents in FAMES. The mechanism allows the flow control agents to do cooperative work without tight dependency, such as name specific communication represented by message passing. We show how the loose coupled flow control agents cooperate via a black board. A prototype of the system is implemented and the proposed functionalities are verified.