Variety of service integration concepts have emerged during the last few years. Most of these aim at the concept of integrating telecommunication and the data communication technologies. One form of such a system is Unified Messaging. Unified Messaging enables users to manage their messages independent of location, communication device or communication medium. Most of the existing systems provide centralized message-store based access to messages but lack services like user personalization, message notification and are non-pervasive. In this paper, we define UMS as a user-centric system that provides messaging services based on user demands and preferences. We have proposed a decentralized Unified Messaging System (DUMS) that is pervasive and context-aware. Based on our proposed architecture, we successfully implemented and demonstrated a messaging system called i- UMS that ensures a user receives almost instantly all messages such as emails, instant messages and so on in an intelligent and most appropriate manner.