And note that if you're behind a NAT box, and running the sort of "semi" split DNS necessary to make lmtp not crap out (in my case, an IP alias of your public IP on your private ethernet interface) then you need lines in your /etc/hosts file for *both* IPs, with the private one first. (In fact, John, what I got was the opposite: since I remembered to put the alias in *before* running the install, that was what Zimbra put in /etc/hosts: *only* the public one).
It continues to irk me that Zimbra's install assumes that if the machine is benjamin.baylink.com, that it will be answering for email for benjamin.baylink.com; in a properly administered network that is *never* the case. And indeed, that's what it reports as the admin email address:
admin@benjamin.baylink.com, an address which is *purposefully* not deliverable here.