[CentOS] Bind Problem

I have a DNS server which is not returning mx queries for some reason? The zone file is as follows:

$TTL 1H
@       IN      SOA     example.com.    root.example.com. (
                                                1       ; serial#
                                                3H      ; refresh
                                                1H      ; retry
                                                1W      ; expire
                                                1H )    ; minimum
                        NS      ns1.example.com.
                        MX      10 mail
                        TXT     "v=spf1 a mx include:isp.com -all"

example.com.            A       aaa.bbb.ccc.ddd
ns1                     A       aaa.bbb.ccc.ddd
mail                    A       aaa.bbb.ccc.ddd

The server is setup as with a caching only configuration with recursion turned off.
Anyone have any idea what could be wrong?

Thanks!
jlc