How can I receive the public mail use zimbra?

[yorry]

help!
There is a zimbra 7.0 server behind firewall .

the zimbra 7.0 IP is 192.168.29.133 .no public IP.
a part of file config in named.conf:
zone "test.gicp.net" IN {
type master;
file "test.zone";
};

and a part of file config in test.zone
$TTL 86400
@ IN SOA @ mail.test.gicp.net. (
42 ; serial (d. adams)
3H ; refresh
15M ; retry
1W ; expiry
1D ) ; minimum

@ IN NS mail.test.gicp.net.
IN MX 10 mail.test.gicp.net.
mail IN A 192.168.29.133
Now the zimbra 7.0 server is ready to user. but the mail can send .but no receive. thanks