Adding Someone To Conversation
When you add other people to a conversation, they must use the same type of Messenger account that you are using. For example, if you are in a conversation with another user using your Communications Service account, you can add only other Communications Service users to the conversation. Likewise, if you are in a conversation with a .NET Passport account user, you can add only other .NET Passport users. (If you point and hover over a contact on your list, a ToolTip will show you which service that person uses.)
1. In the conversation window, click Invite Someone to this Conversation under I want to.
2. Click the name of a contact, or click Other and then type someone else's complete e-mail address.
3. Click OK.