I don't know too how it is possible to do a backup mailing queue in case of (for example) an internet provider failure. I suppose trying to do a second machine, and use some DNS configurations, you could at least making that the mails arrive at the second server, with a second user config on the second server. If it reflects the first one, all users will then have 2 boxes, one on each server, and the second a "temporary queue" of the first one. But ... how could you re-send mails to the primary mailbox when things goes right ?
Maybe I'm wrong way ... But I'm searching a solution too for using a second "all server backup" (not only mail) by myself in case of temporary internet deconnection by my ISP.
Anybody can help ?
Regards,