[ADD] Discuss: new doc for external email servers

Also, misc imp to make discuss doc more business oriented

discuss/tracking.rst

@@ -1,10 +1,45 @@
-:banner: banners/discuss.jpg
+======================================================================
+How to follow a discussion thread and define what I want to hear about
+======================================================================
 
-========
-Tracking
-========
+How to follow a discussion thread
+=================================
+You can keep track of virtually any business object in Odoo
+(an opportunity, a quotation, a task, etc.), by **following** it. 
 
-.. toctree::
-   :titlesonly:
+.. image:: media/discuss07.png
+    :align: center
 
-   tracking/tracking
+How to choose the events to follow
+==================================
+You can choose which types of events you want to be notified about.
+The example below shows the options available when
+following a **task** in the **Project** app.
+
+.. image:: media/discuss08.png
+    :align: center
+
+How to add other followers
+==========================
+You can invite other users and add channels as followers. Adding a
+channel as a follower will send messages posted in the chatter to the
+channel with a link back to the original document.
+
+.. image:: media/discuss09.png
+    :align: center
+.. image:: media/discuss10.png
+    :align: center
+
+How to be a default follower
+============================
+You are automatically set as a default follower of any item
+you create. In some applications like CRM and Project, you can 
+be a default follower of any new record created to get notified
+of specific events (e.g. a new task created, an opportunity won). 
+
+To do so, start following the parent business object
+(e.g. the sales channel in CRM, the project in Project). 
+Then, choose the events you want to hear about.
+
+.. image:: media/sales_channel_follow.png
+    :align: center