OK, as you've already said the hosts file is correct.
I'm not sure which domain you want to host your zimbra server on, is it sitediscovery.com? If that's where you want mail sent to then you don't have any MX records pointing to your server, are you able to make changes on that DNS server that hosts your records?
I also don't understand where sbcglobal.net comes into this, isn't it your ISP?
