There ahs not much to be implemented. Just set the mx records of the domain to the ispconfig server and then create a domain route (transport) in ispconfig that forwards the email to the destination server. In case that the dest server is down, ispconfig will store the messages until the dest server is online again.
So if the ISPConfig server is only used for mail relay it does not even need DNS settings? Only the Advanced Email Routing?
In this case, doesn't changing the MX record to the main ISPConfig server cause now that server to be the single point of failure? I'm just wondering how this behaves like a backup MX in this case. For instance, we have 2 ISPConfig servers running in multi-server mode ... so www1 is master to www2 but both have different customers on them. I want to make www1 the MX backup for domains on www2 and vice versa so that they back each other up. In this case i would put 2 MX records in for each domain with different priorities ... is the routing the way to do this? or is there some other method in ISPConfig. Thanks,