Control the display of each group's specific post via RSS from RSS SETTINGS on the Group Settings page. To get there, click on Settings from the group page:
Navigate and expand RSS SETTINGS:
You can also control what topics are displayed on the RSS feed by checking or unchecking the Enable RSS Feed box for each individual topic:
NOTE: When a message is posted it will automatically be sent to that groups specific RSS feed URL. It can be turned off as described above.