Seems reasonable. I have been thinking about schemes for backup mx'es. When the primary is online, the backup would just forward the smtp connections to the primary directly. The backup mx only has to do their own work when the primary is down. I was/am concerned about the backup mx accepting spam that you don't really want to bounce later on. But that should be an exception.
I am also thinking about synchronizing all the data to another machine. It would allow a manual failover procedure. And it's nice to have another machine (IP) for outgoing email in case the primary IP gets on a block list. But this is all future work.
I am also thinking about synchronizing all the data to another machine. It would allow a manual failover procedure. And it's nice to have another machine (IP) for outgoing email in case the primary IP gets on a block list. But this is all future work.