One of the benefits of the system that yahoo groups uses is that a list can be set up so that if anybody sends to it, they are automatically removed - this facility also used to be provided on some email listservers - you thus can use it as a 'newsletter' list. Moderation can be provided/removed for the whole list or any individual on the list.

I note that comment has been made about very large lists supposedly not working well with Yahoo - the Chiff & Fipple Whistle Newsletter list has several thousand members - I never heard of any problems you mention with it.

Robin