[CentOS] Bind Recursion and Sendmail

Sam Drinkard sam at wa4phy.net
Sun Mar 26 03:57:40 UTC 2006

Aleksandar Milivojevic wrote:

> Sam Drinkard wrote:
>> At the suggestion of some notes on DNSReport.com, I tried turning 
>> recursion off and when I did, it broke sendmail.  All of my upstream 
>> DNS' have recursion turned on, and from what I gather about the mess 
>> there is a chance of dns poisoning with recursion on.
> You can turn recursion off only on name servers that will answer 
> queries from other name servers.  You can not turn recursion off on 
> name servers that answer queries from clients.
> The resolver library is not supposed to perform recursion itself. 
> That's the job of name server.  That's why it broke your Sendmail.  
> The resolver libraries are usually too dumb to perform recursive 
> lookups them self, and might be even prevented to do so by firewalls.  
> Also, it would be waste of your network bandwidth since you'd loose 
> effects of caching that name servers are performing.
> Said that, on name servers that are supposed to answer queries from 
> clients, you should be able to allow recursion only for specific 
> clients.  If you have a valid reason to do so.  That basically means 
> name server will not be particularly useful to clients not on the 
> list.  This might be a good idea if you have only one name server, 
> serving both internal network and Internet (not such a good idea, IMO).
> Question for OP, what's the content of /etc/resolv.conf?  Do you have 
> "nameserver" inthere by any chance?  That would explain why 
> it hasn't worked, since was not on the list of hosts allowed 
> to do recursive lookups.
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

    Thank you for the info.  That does make sense now that I think of 
it.  I guess I tend to believe everything I read from certain places 
without question, and that sometimes turns out to bite me in the 
rear-end :-)


More information about the CentOS mailing list