We've had a problem with these folk:
> Received: from 200-158-48-52.dsl.telesp.net.br

also.     Last week they managed to get some of their stuff relayed through
the list site, as if it were actually distributed by the lists in question,
when in fact it wasn't.  It would, though, fool the not too observant into
thinking it *did* come via the lists.  I don't know about anyone else,
but I always put the name of my lists in the filter of their headers.

Douglas Winship