> >> I'm not sure that this is  desirable. For one thing, it isn't consistent:
> >> the results would depend  on whether the lists are on  the same server or
> >> not.  The subscriber  could have  a  filter to  log the  mail in  various
> >> folders based on  which list it comes  from, and in that case  one of the
> >> two folders  would be selected  randomly to  receive the message,  and it
> >> wouldn't be in  the others. Again, while this saves  disk space, it isn't
> >> very consistent. It isn't even consistent with news where, while there is
> >> only one copy of the message, it will be shown in both newsgroups. With a
> >> mail interface this will not be the case.
> >
> >I'm subscribed to a lot more lists on our own server than any other and
> >there is a fair amount of cross posting, so it would help quite a bit
> >in a common case here.
> >
> >With regard to the filtering, the headers should mention both lists.
> >Wouldn't that take care of it?
>
>    And,  what happens  if  I am  subscribed to  2  lists with  different
> options  (such as  NOMAIL/MAIL or  DIGEST or  such things  as yet  to be
> invented)?
 
In cases like that, LISTSERV would still deliver two copies.
On our server that's the exception -- most lists use the defaults.
 
>    What if it is sent to two lists, but I want to follow-up to one list?
 
If the headers mention both lists, your client could allow you
to select only one list for your reply.  As it is now, it's
difficult to follow up to more than one list.