Problem with hosting providers reverse DNS

[andrewgroups at gmail.com]

When I run a reverse DNS search on our hosting provider,  this error
"WARNING: Duplicate zone found ..."  appears randomly.  Some email
server are blocking us and I suspect it is because they have something
that is not well configured.  Can anyone figure out what the problem is
and why this "Duplicate zone found" error is returned?


Preparation:
The  reverse DNS entry for an IP is found by reversing the IP, adding
it to "in-addr.arpa", and looking up the PTR record.
So, the reverse DNS entry for 216.133.255.56 is found by looking up the
PTR record for
 56.255.133.216.in-addr.arpa.
All DNS requests start by asking the root servers, and they let us know
what to do next.
See How Reverse DNS Lookups Work for more information.

How I am searching:
Asking i.root-servers.net for 56.255.133.216.in-addr.arpa PTR record:
       i.root-servers.net says to go to figwort.arin.net. (zone:
216.in-addr.arpa.)
Asking figwort.arin.net. for 56.255.133.216.in-addr.arpa PTR record:
       figwort.arin.net [192.42.93.32] says to go to
dns-01-002.root-dns.com. (zone: 255.133.216.in-addr.arpa.)
Asking dns-01-002.root-dns.com. for 56.255.133.216.in-addr.arpa PTR
record:
       dns-01-002.root-dns.com [64.7.192.163] says to go to
dns-01-001.root-dns.com. (zone: 255.133.216.in-addr.arpa.)

WARNING: Duplicate zone found (zone 255.133.216.in-addr.arpa. is
repeated).  This can prevent the lookup from continuing
         (BIND8 and BIND9 will cause a 'server failure' response).
Although I will continue, be aware that
         most DNS servers will not see your reverse DNS entry.

Asking dns-01-001.root-dns.com. for 56.255.133.216.in-addr.arpa PTR
record:  Got CNAME referral to 56.0/24.255.133.216.in-addr.arpa. at
server dns-01-001.root-dns.com. (zone 0/24.255.133.216.in-addr.arpa.)
[from 64.7.192.162]
Asking d.root-servers.net for 56.0/24.255.133.216.in-addr.arpa. PTR
record:
       d.root-servers.net [128.8.10.90] says to go to henna.ARIN.NET.
(zone: 216.in-addr.arpa.)
Asking henna.ARIN.NET. for 56.0/24.255.133.216.in-addr.arpa. PTR
record:
       henna.arin.net [192.26.92.32] says to go to
dns-01-001.root-dns.com. (zone: 255.133.216.in-addr.arpa.)
Asking dns-01-001.root-dns.com. for 56.0/24.255.133.216.in-addr.arpa.
PTR record:  Reports NET-allocation-00025443.ix.sitestream.net. [from
64.7.192.162]

Answer:
216.133.255.56 PTR record: NET-allocation-00025443.ix.sitestream.net.
[TTL 86400s] [A=None] *ERROR* There is no A record for
NET-allocation-00025443.ix.sitestream.net. (may be negatively cached).

To see the reverse DNS traversal, to make sure that all DNS servers are
reporting the correct results, you can Click Here.