You should definitely get yourself subscribed to VMSHARE :-) I've heard a
lot of horror stories  about HPO5 on it. For example,  once the PRG abend
during WARM start is  fixed, you may find out that  CKPT doesn't work any
more if  you have done a  successful SHUTDOWN/WARM start in  the past. As
long as you use only a combination of COLD and CKPT starts, it works. But
if you ever dare to do a WARM  start, you won't be able to CKPT any more.
That's just one of the horror stories of course :-)
 
In any  case, LISTSERV can work  under release 5 without  problem (unless
you remove  both UCENG  and AMENG),  as long  as CP  and CMS  are working
properly.
 
  Eric