I am planning Zimbra installation on Clustered environment with one head node and one compute node. I would like to use Zimbra NE. Can any one suggest server sizing like Min RAM to support 1500 Mail boxes. I have seen that in an environment with 2GB RAM and 30-40 mail boxes the RAM utilization is around 1.5 GB. I am looking at suggestions on RHEL 4.5 with Cluster suite and Zimbra NE 5.0.5. 2 servers 1 san and 1 tape. MAX size for mail boxes would be 2GB. Most of them use WebUI.