Firstly – it won’t be an app. It will be built into the phone’s Messaging Hub. There’s no need to download a separate app, and no separate experience to navigate – have all your contacts ready for messaging or texting in one location.
It will come with a chat feature, which brings the best features of the desktop client over to the mobile phone. You’ll have emoticons, multiple points of presence, and you’ll be able to chat with all your friends regardless of whether they are on the PC, in Hotmail or on other devices. It will also feature integration with Facebook Chat – no more launching a separate app just to chat with your Facebook friends – do it right from the Messaging Hub instead.
Users will also have the ability to perform seamless switching depending on who they are chatting with. Windows Phone will automatically pick the richest service for both parties to use to chat, but users will have the option of switching to another service manually. Photo sharing, group chat, and voice to text will also be new features of Messaging.
All in all, it makes Windows Phone 7 Mango shape up to be a really sweet upgrade; especially for those who are heavy chatters/texters. Visit the Windows Live blog for more detailed information.