I was making the assumption earlier that you are running your own DNS server, is that correct? If you're hosting it locally you should be able to set-up BIND to find your servers. If you have your current mail server records hosted on an outside DNS server then you'll need to set-up BIND locally and run a split-DNS system.
The error you poted earlier has this text in it:
which indicates to me that there's a DNS problem.
com.zimbra.cs.service.ServiceException: operation sent to wrong host (you want 'server.com')