Help please: how to avoid cross posting

[Ellen . S]

Can someone tell me how to set mozilla to show the newsgroups a reply
meesage is being posted to and how to edit the list to eliminate cross
posting?   Thank you for your help.  

I have done a web search and posted a request at netscape but they
replied they do not handle this question and the Mozilla handbook
online states that the reply automatically chooses all the newsgroups
the message was posted to and did not indicate how to change this.

Ellen S