Routing email within the domain

[Michael J. Allen]

To All:

In my 'test.org' domain I have two Cyrus email servers:  server1 and 
server2.
There are two email boxes: boxa on server1 and boxb on server2.

I want to address email to the 'test,org' domain like this:

        boxa at test.org and boxb at test.org

I have established two MX records in DNS like this:

        mail1    MX  10  mail1.server1.test.org
        mail3    MX  20  mail2.server2.test.org

Only email to boxa on server1 actually gets delivered.  What am I doing 
wrong?

Any help will be appreciated.  Thanks in advance for any help you can give.

Mike