Add a secondary MTA

[Vai0l0]

I'm currently running a Network Edition 5.05
running in a vmware guest system.

I have 2 vmware server and 8 hosts running on the 2 server (4 on each)

every night I pause each vm and I do a full copy of the vmware machine on the other vmware server.

In event of a severe hardware failure on one of the two vmware server
I should be able to continue to run the 4 guests originally hosted by the live server and restart the copies of the guests running on the server that failed

unfortunately pausing the zimbra guest server, stops the MTA

I'd like to setup a secondary MTA that could act as a backup MX that receive the mail and deliver to the main server once it has restarted.

I've looked to the multiserver installation guide but does not seem to help in linking the two servers defining a primar and secondary MX

Does Zimbra really autoconfigure itselfs only based on the dns mx entry in the domain?