We've been migrating from one zimbra server to a hosted provider via imapsync. We have not made the MX record change yet, but it is proving difficult to keep the two servers synced up.

Is it possible to have our old server (still in production) duplicate copies of messages to the new server's IP? Since it has the appropriate domains set up, I imagine it would be able to route the mail once received.

I'm thinking of something like an always_bcc, but to a server rather than a mailbox.