Blacklist Domain, Whitelist Sender

[airborne180]

User here, mostly accessing via web GUI. Some time ago, I was receiving a significant amount of phishing etc. from a specific (large) domain, which I blacklisted. I recently encountered a person using this domain for email, and their correspondence was bouncing, appropriately. I understood that whitelisting their email address would permit their specific address to bypass the domain restrictions, but this did not happen. The solution according to my ISP tech support contact is to remove the domain blacklist, which might be okay for now.

The question remains: Why didn't the blacklist-domain/whitelist-address approach work?

As a GUI user, I may not have access to the command-line tools that I see under discussion.

Grateful for any insight,
-Steve