They will be coming up with further enhancement so that you will able to use it with yahoo main, Gmail etc.
As per them:
Xobni is the Outlook plug-in that saves you time finding email conversations, contacts and attachments.
After a quick install, you'll see the new Xobni toolbar appear in Outlook - and suddenly information will become much easier to find. When a new email arrives, the sender's full communication history appears in the Xobni sidebar, including past conversations, attachments and contact details. Xobni also includes a blazing fast email search tool.