Direct delivery mail receiver: whitelists?

hi,

I saw how to blacklist some domains in the mail-receiver container
qq.com REJECT
163.com REJECT

but similarly, is it possible to whitelist some domains only and automatically blacklist all the others?

I am using Discourse as an internal discussion forum and would like to auto-reject all those domains that don’t belong to us.

thanks

This is a postfix issue, so you might search postgres documentation.