Performance tuning bind

[Michael Cunningham]

Folks,

I am having some problems with some very high volume mailservers 
we have that have been failing to get responses from our dns servers
before udp timeouts occur. We have a Ultra 5 with 128 meg of ram which is
basically totally idle which is serving dns only. The other dns server is
on our outbound mailserver. They were both 4.9.4 which came with Solaris.
We upgraded to  8.2.2p5 in the hope that this would help our dns timeouts
but no luck. It has gotten a bit better though. Both Solaris 2.6 systems
are fully patched with the latest clusters. Is there something I can do to 
a system to improve it dns serving ability or performance tune bind
somehow?  The Ultra 5 system is basically idle 99% of the time. Could
it be something else? 

These are the errors I am getting from communigate pro MTA. Any ideas?

14:58:04.57 4 SMTP-48450(memailin1.messagereach.com) failed to find
relays: no DNS MX-data returned
14:58:04.97 4 SMTP-48451(post.pl) failed to find relays: no DNS MX-data
returned
14:58:05.02 3 DNR got response from [137.236.4.7] for an unqueued request
15019; discarded
14:58:05.12 4 SMTP-48452(thc.com) failed to find relays: no DNS MX-data
returned
14:58:05.21 3 SMTP-48452(thc.com) failed to resolve 'thc.com':Error
Code=no DNS A-data returned
14:58:05.38 4 SMTP-48454(memailin1.messagereach.com) failed to find
relays: no DNS MX-data returned
14:58:05.79 4 SMTP-48455(networkers.ch) failed to find relays: no DNS
MX-data returned
14:58:05.80 4 SMTP-48457(memailin1.messagereach.com) failed to find
relays: no DNS MX-data returned
14:58:07.96 3 DNR got response from [205.183.255.229] for an unqueued
request 15210; discarded

Thanks.. Mike