I'm using Virtualmin on a machine behind NAT, with a single ethernet interface that uses 192.168.1.201.
If I set my "Default virtual server IP address" to the external IP (188.8.131.52), DNS comes out fine but Apache doesn't listen on the right address, so I have to change the Apache virtual servers by hand.
If I set the "Default virtual server IP address" to the real address of the machine, Apache is happy, but DNS gets all screwed up. I have tried using the "Default IP address for DNS records" but that isn't consistent. It doesn't properly apply to SPF records, for example, or to customized records.
Its seems there are two problems:
1) "Default IP address for DNS records" should always apply if it is set.
2) There should be a way to override the default IP for Apache virtual servers.