...It worked fine, but the first time the owner of the list made changes in the GUI, the configuration file was over-written and the restrict_post was changed back to the name of the mailing list. Is there a solution to this that would still allow the end-user to use the GUI to make changes to the list of recipients but maintain the restriction I am trying to apply?
Name the file list_name.post (and specify it as such in the list_name.config).