Here's what I'm trying to achieve with a multi-server configuration. Having looked at the docs, I'm not clear whether I can do it with Zimbra. I'd like to know whether I can and, if I can't, what's the best I can do.

I want to run two Zimbra servers at different locations, such that
  • Both servers are part of the same mail domain
  • All users exist on both servers, so a user can log onto either
  • Data is syncronised between the servers
  • If one server fails, all users can use the other server