I'm not sure if I'm using the correct terminology regarding this question.

I have a zimbra server running at a site. What we'd like to have is a backup server in case the primary server goes down for any reason (broadband connection is broken, no power to building, etc).

The emails would automatically go to the backup server. Users can see their emails on there. When the primary server comes back online, the emails queued on the backup server automatically get sent to the primary server.

Is this possible with zimbra?