David,
 
There is  an IGNORE= setting  in LSV$PROF which,  I believe, allows  to specify
which userid@nodes  should be never replied  to. W.r.t. the sugestion  of Gary,
I'm  running  the EB0UB011  LISTSERV  with  SET WNG  ON  (*not*  IUCV) and  had
experienced no problems since July, where the LISTSERV was installed.