Running BIND on a mail server?

[Andrew Fleming]

I have just finished making a lot of changes to my named.conf and
zones, and it has got me thinking about performance.  Two of my mail
servers have DNS servers running on them, however my other two mail
servers (which are my main two) do not.  They are using the first two
servers for DNS lookups.  

Because of spam I have full DNS verification enabled on all of my mail
servers.  I am thinking about running DNS servers on all of my mail
servers, because I know that having full DNS verification creates a
lot of DNS traffic.  That way they would have local cache and cut down
the time an traffic on the network from this.  Any comments?  

If I installed DNS servers on my main two mail servers, I had thought
about using the forward option in BIND 8 to have them forward requests
to my main two DNS servers, so the could take advantage of their cache
also, and possible cut down some of the DNS traffic on our Internet
link.  

If anyone has any comments about if this is a good idea or bad idea,
please post them, and an explain your thoughts.  

Thanks in advance

Andrew Fleming
f236 at scatcat.fhsu.edu