On 3 Sep 2018, at 4.18, Daniel Miller <dmiller@amfes.com> wrote:

That works for a one-time migration, or perhaps via a cron-job, but what I want is basically a constant one-way backup and it seems replication could do it more elegantly & efficiently.

So you want real-time archiving? What we have done with couple of customers is that we just configure MTA to replicate all incoming mails to secondary site.

Sami