I have installed zimbra on our home server, it was a bit of a hassle, because we don't have a local dns server running.
Our situation is as follows, we have a router, with all the necessary ports forwarded, and a server running behind that.
The installation gave quite some errors involving the DNS, but in the end, I managed to get the installer to complete successfully with the help of bind9.

I think its solved it as following, when the installer requests the ip in the mx records of our provider, bind9 says its local, since thats the same ip as our machine, it succeeds.
So we have the webclient running now, the only problem is that we cannot send or receive mail from/to the outside. From one local user to another works fine.

Do you have any idea in what direction to look to tackle this problem?

I have installed zimbra 6.08 on an ubuntu 10.04 installation (64 bit)

Thanks in advance for your help.