Block everything except 2 domains in Spam Assassin

One of our spamassassin servers is getting smashed by tons of Russian spam and causing a failure when we're trying to process the emails we care about. I'm trying to reject all email that isn't on 2 specific domains, but not sure why it isn't working properly. I went through the config and added the following, but it doesn't see to make any changes after service restart. In: local.cf i've tried 2 changes: blacklist_to *@* un_blacklist_to *@domain1.com un_blacklist_to *@domain2.com And this one... whitelist_to *@domain1.com whitelist_to *@domain2.com blacklist_to *@* I thought I would have seen some of these changes go through rather quickly but it doesn't seem to change anything. The spam email is coming in with pretty low sizes and the email I care about needs to be over 50k. Even if I could figure out how to reject all email over 50k, that would work. Thanks for any help on this. Going to keep looking at solutions while in this bind...