Hi,
yes, you can add the respecitve mail domains to the Whitelist Who object, then go to the Mailfilter and change the priority of the default present whitelist rule to 100. Then add a new rule which has simply a "Block" action object with priority 99.
So, the whitelist has the highest priority, all mails matching it will be accepted. All remaining mails will get matched by the second-highest priority rule and be blocked.