Hi to all, What I have: I use the ISPConfig administration panel for the server on which we have mail. Problem solved: Now I'm working on how to create a backup MX server, which I would put in the DNS command of the main MX server, just with a different priority. As a result, if the primary MX server fails, mail should be routed to the backup MX, where the messages would be stored and waited until the primary MX server responded again. An idea of how this should be handled: Ideally, I would handle this without replicating a MySQL database with data on user mailboxes. Apparently this is done only so that the backup server immediately discards mail destined for a mailbox that does not exist on the primary MX server. I don't think it's necessary. I would most like to solve this by deploying a container with some SW that is used for that. That the container / other VPS would serve as an MX backup. Thank you so much for the tips and advice.