Offsite Zimbra MTA in Multi-server Environment

[mhammett]

I have a multi-server Zimbra environment.

I'd like to spin up a geo and network diverse Zimbra installation to more or less be a backup MX.

I want more than your standard dumb MX (which is what I see in all of the Zimbra backup MX guides, posts, etc.). I want it to authenticate and hold the incoming mail until the appropriate mailbox server is online, then deliver it. No point in holding mail for accounts that I don't have.

I need to specify an authentication server, which is a mailbox server. Obviously, I can't point at one of the existing mailbox servers as the point is to be diverse from that environment. I'd need a new one. I don't want to have provisioned mailboxes on that server. It's just supposed to be used for off-site LDAP replication and MX.

How can I best accomplish what I'm after?

[mhammett]

Also, the dependency of the MTA on a mailstore server seems... not well thought out. I don't see why it couldn't authenticate directly to LDAP.

[mhammett]

It looks like I could put an MTA on that server and then just make sure that it isn't a permitted host in any of the COSes.