FreeBSD + BIND 8.2.3

[A. David Perez Marfil]

hi list ,
 i got a FreeBSD server for DNS service,
the problem is that the server could not resolve some MX records.
the server is behind a NAT.
here is my configuration file is this fine?
well thanks for any comment.

-----------named.conf-------------------------
options {
        directory "/etc/namedb";
        statistics-interval 60;
        allow-query { 172.19/16; 172.20/16; 172.21/16; 172.22/16; };
        allow-transfer { 172.19.14.30; 172.22.16.2; };
};

zone "." in {
        type hint;
        file "named.root";
};

zone "0.0.127.in-addr.arpa" in {
        type master;
        file "localhost.rev";
};

zone "unimayab.edu.mx" in {
        type master;
        file "db.unimayab";
};                                

zone "21.172.in-addr.arpa" in {
        type master;
        file "db.172.21";
};

zone "uax.edu.mx" in {
        type slave;
        file "db.uax";
        masters { 172.22.16.2; };
};   

zone "anahuac.mx" in {
        type slave;
        masters { 172.19.14.30; };  

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