VM traffic monitoring

what is "smtp node"?

a new 2.0 feature? (still not tried 2.0 but damn curious :-) )
Node server system to open the SNMP, is not smtp node.And then use the cactiand the like monitoring software can monitor the VM traffic within the node.The original has been using Hyper-V or VMware when monitoring VM traffic anguish, suddenly found proxmox2.0 can monitor the VM traffic, so very excited.
Sorry, my English is not good.