Joan may well be correct that these were error messages rather than
duplicate postings and the subcribers didn't know the difference. However,
Mauri described them as duplicate postings, not errors. We've had problems
on MEDLAB-L with such in the past.
 
If they were error messages, and they were sent to the list and the
list distributed them again the header perhaps needs to be reconfigured.
And maybe put in a filter for the address.
 
If they were error messages mistakenly sent to the individuals who posted
the original messages there is little you can do about it other than
deleting the offending subscription, gripe at them, and tell your
subscribers to ignore the garbage (if they must gripe, do so to you and/or
the offending site, not to your list, please ;-)  ).
 
More detais are needed (are *all* subscribers getting them? are they
truly repostings or are they error messages? etc.)
 
Whatever the case, the first step would surely be to block the offending
site.  If that means getting rid of usenet or whatever gateways, well,
it's your list; if the gateways cause problems you would rather not
deal with just get rid of them.
 
Douglas
       Douglas Winship   Hays County, Texas  [log in to unmask]
                    Secondary AUTOCAT Listowner
                              MEDLAB-L