All servers in a cluster must run one of the following: the Lotus Domino 6.5 or Lotus Domino 6 Enterprise server, the Lotus Domino 6.5 or Lotus Domino 6 Utility server, the Domino Release 5 or Domino Release 4.62 Enterprise server, or the Domino Release 4.6 or Domino Release 4.5 Advanced Services server.
Note Earlier releases of Domino do not have access to features that are new in Domino 6 or 6.5.