[CentOS] one server handled sendmail added two more servers messes things up

Hi all,

I had one server running centos 4.7 i686  everything was fine with 
incoming mail.

I now added two more servers centos 5.4 x86_64 and gave them machine 
names all
part of the same domain as machine 1. I noticed that incoming emails are 
being
round robined to all three machines.  At this time I really just want 
the one original machine
to handle my incoming email... The other two new machines are for other 
purposes.

How do I tell the two new machines that all incoming email send to 
machine 1.
Is there an easy way to do that? At this point I just turned off the two 
new machines
and all mail is coming into the original machine just like before.

Thanks,

Jerry