From what I heard of VMSHARE, HPO 5.0 simply doesn't work. "If you plan
to install HPO 5, please locate the nearest brick and hit yourself hard
on the head. You will find it to be a much more productive use of your
time" (that's probably not the exact quotation but I think it's close
enough). So the issue of whether or not LISTSERV will work under HPO 5.0
is a bit academic :-)
Eric