>>> How do I make sure it is working? After I configured like below, I >>> restarted amavisd and postfix and I am seeing a lot of >>> ``RelayedOpenRelay'' like below..
Perhaps this doesn't apply to the OP, but I can't tell given the question. Whitelisting only applies to other checks, but DOES NOT apply to banned-files. There's no way [or any generally effective way] to whitelist banned files based on sender addresses/domains. [As a result of experience, in trying to find a way to whitelist some senders for banned-files and failing to find a way native to/in Amavis, I've developed a script that "adds" that functionality. But it's not in Amavis-new.]
