In a mobile agent system, communication protocol is a key mechanism since agents need to communicate each other to achieve their joint goal. Many researches are studying mobile agent communication in order to provide a reliable communication protocol for mobile agents. In this research, we investigate communication issues among mobile agents, and propose a distributed sendbox approach based on Session Initiation Protocol (SIP) as the signaling protocol. The distributed sendbox scheme offers two modes. Direct mode is used when receiver agent is stationary, whereas forward mode is invoked as receiver agent is moving. A prototype system is developed, and experiment results are also presented.