Checkpoint version is addon load balancer module called ConnectControl.
http://www.checkpoint.com/products/d..._DataSheet.pdf However, cheaper alternative is to use LVS on linux for that.
http://perlstalker.amigo.net/courier/Cluster/LVS.phtml Just ignore the gentoo specific stuff. and just follow instruction on SMTP port 25 and set up config for your SMTP servers.