Configuring reverse DNS on BIND 9.7.3

I'm seeing the following in /var/log/mail.log

UPDATE :I own the mentioned public IP addresses.

The IP address sending this message does not have a PTR 550-5.7.1 record
setup. As a policy, Gmail does not accept messages from IPs 550-5.7.1 with missing PTR records.

I need to setup reverse DNS by configuring PTR records on my DNS server and I'm having a hard time figuring what I'm doing wrong.

So far I have added in /etc/bind/zones/example.com.db

$TTL 86400; 1 day
@               IN SOA  a.ns.example.com. admin.example.com. (
                                2016090901 ; serial
                                60         ; refresh (1 minute)
                                7200       ; retry (2 hours)
                                3600000    ; expire (5 weeks 6 days 16 hours)
                                86400      ; minimum (1 day)
                                )

1.196.198.in-addr.arpa. IN NS a.ns.example.com
1.196.198.in-addr.arpa. IN NS b.ns.example.com

11              IN      PTR mail.example.com
6               IN      NS      a.ns.example.com.
9               IN      NS      b.ns.example.com.
                        MX      5 mail.example.com.
mail                    A       198.196.1.11
mx                      A       198.196.1.11
smtp                    A       198.196.1.11
www        60     IN    A       198.196.1.22
example.com. 60   IN    A       198.196.1.22

and in /etc/bind/named.conf

  GNU nano 2.2.4                                                       File: named.conf                                                                                                                      

options {
        directory "/var/cache/bind";

        auth-nxdomain no;    # conform to RFC1035

        listen-on { 198.196.1.6; };
        listen-on-v6 { "none"; };

        recursion no;

        allow-transfer { 198.196.1.9; };
        also-notify { 198.196.1.9; };
};

controls {
        inet 127.0.0.1 allow { localhost; };
};

zone "example.com" {
        type master;
        file "/etc/bind/zones/example2.com.db";
};

zone "example.com" {
        type master;
        file "/etc/bind/zones/example.com.db";
};

zone "1.196.198.in-addr.arpa" IN {
type master;
file "1.196.198.in-addr.arpa";
allow-update { none; };
};

and still when I do a PTR lookup I'm getting

dns2.xxxx.xy  x.x.x.x  AUTH  140 ms  Received 1 Referrals , rcode=NAME_ERROR    1.196.198.in-addr.arpa. 14400 IN SOA mname=dns1.xxxx.xy rname=hostmaster.xxxx.xy serial=xxxxxx,