- Log in to the list admin page at http://yourdomain.com]/mailman/admin/listname
Click on Privacy Options
Click on Sender Filters (in the list of links under Privacy Options)
Scroll down to the question "By default, should new list member postings be moderated?" and click "Yes"
Choose Hold, Reject or Discard for "Action to take when a moderated member posts to the list." (read a description of these choices by clicking on "Details for member_moderation_action")
Set any other desired preferences on this page and submit the changes
Click on Membership Management (at the top of the page)
Under "Additional Member Tasks" set everyone's moderation bit to "On" and click Set
Make sure the address which is authorized to post to the list is a subscriber (if the address is an owner, but not a subscriber, it won't work)
Search for this authorized address in the list of subscribers and set the moderation bit to "Off" for this subscriber
Now the only address which is allowed to post to the list without moderation is the one you designated in the steps above.