When you distribute a Lead to a Partner User from within Channeltivity, that User will immediately receive an email notification (you can configure this at Settings > Lead Distribution > Lead Email Notifications). The email will not include any information on the Lead details. This provides an incentive for the Partner to log into your Channeltivity partner portal.
Lead Email Notification
Once the Partner User logs into Channeltivity and views the Lead, its status will change from "Unopened" to "Opened".