I may have missed something, but isn't this problem addressed by
setting the list to Private?

> My concern was why we go to the subscrption process if anyone can
> send a message to the list even if he is not subscribed to it?

This, and the fact that I think spammers are less interested in lists
these days since they can harvest email addresses elsewhere, has
apparently pretty well solved the problem for the lists I run.

                                        -- Russ
                                __|~_
Russell A. Hunt            __|~_)_ __)_|~_           Aquinas Chair
St. Thomas University      )_ __)_|_)__ __)  PHONE: (506) 452-0424
Fredericton, New Brunswick   |  )____) |       FAX: (506) 450-9615
E3B 5G3   CANADA          ___|____|____|____/    [log in to unmask]
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      ~~~~~~~~~~~~ http://www.StThomasU.ca/hunt/ ~~~~~~~~~~~~