With the rapid advancement of wireless network technologies, mobile Instant Messaging (IM) has become a major application in the telecommunications industry. The internet-based instant messaging services (e.g. MSN messenger, GTalk) have become the most popular communication choice among millions of people worldwide. Due to the huge number of mobile subscribers, there is a real demand to provide such a service to mobile clients. Despite technology’s significant advantages, the primary disadvantage is that only users who are on the same network can chat with each other on that particular network.