Getting a local domain list for amavisd-new?

I am adding a pre-queue mail filter using amavisd-new, something Virtualmin doesn't support by itself.

Part of proper header-generation with amavisd-new involves generating a list of domains that should be considered as receiving mail locally. Is there a good way of automatically generating a list of local domains that receive mail from the command line with Virtualmin? Is there a file that indexes them?

I don't want to have to add each domain manually to amavisd-new, so I'm trying to concoct some kind of lookup.

And, is a pre-queue mail filter option something that Virtualmin might support down the line?

Thanks!