i have configure zimbra 8.3 with split-dns and bind behind the firewall.
but after configuring this i have able to send mail from zimbra mail server to outside network but can not receive mail from outside network.

live ip=83.136.81.175
firewall ip=192.168.15.254

cat /etc/hosts
127.0.0.1 localhos.localdomain localhost
192.168.15.175 04.securemails.org 04

cat /etc/named.conf
options {
listen-on port 53 { 127.0.0.1; 192.168.15.175; };
forwarders { 192.168.15.254; 4.2.2.2 ;};
directory "/var/named";
dump-file "/var/named/data/cache_dump.db";
statistics-file "/var/named/data/named_stats.txt";
memstatistics-file "/var/named/data/named_mem_stats.txt";
allow-query { localhost; };
recursion yes;

dnssec-enable yes;
dnssec-validation yes;
dnssec-lookaside auto;

/* Path to ISC DLV key */
bindkeys-file "/etc/named.iscdlv.key";

managed-keys-directory "/var/named/dynamic";
};

logging {
channel default_debug {
file "data/named.run";
severity dynamic;
};
};

zone "." IN {
type hint;
file "named.ca";
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

zone "securemails.org" {
type master;
file "securemails.fwd";
};



cat /var/named/securemails.fwd

$TTL 84600
@ IN SOA 04.securemails.org. root.04.securemails.org. (
10118 ;Serial
43200 ;Refresh
3600 ;Retry
3600000 ;Expire
2592000 ;Minimum TTL
)
IN NS 04.securemails.org.
securemails.org. IN MX 10 04.securemails.org.
04.securemails.org. IN A 192.168.15.175

cat /etc/dnsmasq.conf
server=4.2.2.2
server=192.168.15.254
domain=securemails.org
mx-host=securemails.org,04.securemails.org,5
listen-address=127.0.0.1

cat /etc/sysconfig/network-scripts/ifcfg-Auto_eth3
TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=no
NAME="Auto eth3"
UUID=2ec9c9aa-68c8-4f1a-9aa2-155fceb68729
ONBOOT=yes
IPADDR=192.168.15.175
PREFIX=24
GATEWAY=192.168.15.254
DNS1=127.0.0.1
#DNS2=192.168.15.254
HWADDR=00:15:5D:0F:32:02
LAST_CONNECT=1376629401


dig securemails.org mx
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6_4.5 <<>> securemails.org mx
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48096
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;securemails.org. IN MX

;; ANSWER SECTION:
securemails.org. 84600 IN MX 10 04.securemails.org.

;; AUTHORITY SECTION:
securemails.org. 84600 IN NS 04.securemails.org.

;; ADDITIONAL SECTION:
04.securemails.org. 84600 IN A 192.168.15.175

;; Query time: 4 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Mon Aug 19 15:14:01 2013
;; MSG SIZE rcvd: 82

dig securemails.org any

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6_4.5 <<>> securemails.org any
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57044
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; QUESTION SECTION:
;securemails.org. IN ANY

;; ANSWER SECTION:
securemails.org. 84600 IN SOA 04.securemails.org. root.04.securemails.org. 10118 43200 3600 3600000 2592000
securemails.org. 84600 IN NS 04.securemails.org.
securemails.org. 84600 IN MX 10 04.securemails.org.

;; ADDITIONAL SECTION:
04.securemails.org. 84600 IN A 192.168.15.175

;; Query time: 1 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Mon Aug 19 15:14:28 2013
;; MSG SIZE rcvd: 123