I suffered some loss of incoming emails during disaster recovery that I'd like to know how to avoid in case this happens again. Zimbra tech support told me to change DNS records to keep incoming emails from reaching the server. The trouble with this is DNS changes can take time to propagate. I believe emails received after the server was rebuilt, but before the backup data was restored, were overwritten by the restore process.
I'd like to know how to keep the server from receiving mail without unplugging the network cable. Unless I'm mistaken, the server must be connected to the internet (for DNS purposes) while it is being installed.