Presence-based alert policy.
Assembly: Microsoft.Lync.Model (in Microsoft.Lync.Model.dll)
The AlertLevel.NotificationEnabled property tells you whether notification for new group chat messages, conversation invitations, or meeting reminders should be displayed. You do not display such notifications if a user is presenting in a meeting and is sharing a display or presenting a PowerPoint slide deck. In those cases, NotificationEnabled returns false and you must honor the policy.