Deleting WLM News Posts

I'm using Version 2011 (Build 15.4.3508.1109) of WLM.

After I've finished reading usenet posts in any folder what is the proper way to get rid of them so they do not show up the next I open the same folder?

I'm guessing the 2011 version has the same options as 2009. There should be a "Maintenace" Tab under Options with an item that starts "...Purge Newsgroup Messages...". I've never used it myself since I'd be afraid to be missing some posts in a thread that that were responded to in a later post. The old posts give it the proper context.