I hope this is not a stupid question...
I know, in this day and age, how easy it is to get your mail server's IP address on a blacklist. I also suspect that it might be even easier to get blacklisted if users are using the Mailman mailing list feature (which I plan to offer to our customers shortly.)
So, would it be possible or practical to route (relay) mailing list traffic out through our backup MX server?
We have a second Virtualmin GPL on a remote VPS (in addition to our primary Virtualmin Pro box) to provide backup MX services. If one of our IPs was to get blacklisted, even for a very short time, I'd much prefer it to be the backup server.
Also, I think all Virtual Servers already have the backup MX as an authorized sender in their SPF records.