[CentOS] disabling lame server logging

Continuing to 'clean up' my new server by reviewing logged messages.  
Researching a common one:

Feb 26 07:30:29 onlo named[19336]: error (unexpected RCODE SERVFAIL) 
resolving 'foo.com/MX/IN': 1.2.3.4#53

I get the drift that my server has been directed to a 'lame server' and 
logs that fact.  Supposedly I am to lookup the SOA record and contact 
the admin to fix this.  What I really want to do is stop all these 
messages as I suspect I will not be able to do anything to fix the 
problem.  So far what I have found is to add to my global logging section:

     category lame-servers { null; };

Is there a finer scalpel?  I believe there are other lame server 
failures? Like 'RCODE REFUSED' and 'RCODE 15' (these are the 3 I see in 
my messages)?  Can I block logging by RCODE, so as new ones appear I can 
learn what they mean before /dev/null ing them?