what is easiest way to setup a messenging failover system

I'm using iPlanet Messenging server 5.2.If I want a complete failover system what is the best way to go about it?thanks
[148 byte] By [708971] at [2007-11-25 7:13:21]
# 1
A cluster.
708686 at 2007-6-29 17:47:39 > top of Java-index,E-Mail, Calendar, & Collaboration,Sun Java System Messaging Server...