I need to create a messenger in SharePoint 2010 similar to Microsoft live chat support. Any ideas or suggestions on how it can be implemented in SharePoint. I tried SharePoint messenger at CodePlex http://sharepointmessenger.codeplex.com/. For this one, all the users who need to use the messenger have to be added in the group. So if there are around 21K users, then it is quite difficult since all the users will be visible in the contacts list. So any ideas or suggestions?