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I have a mail application running on a Windows 7 machine. I need to allow a reverse lookup, as of right now when a reverse lookup is ran it timesout. Is there a port that needs to be open or software to be installed?

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"nslookup [ip]" works fine for me. Is that what you mean? – Huskehn Aug 16 '13 at 19:49
DNS queries either run from udp\53 - udp\53, or TCP\53 - TCP\ > 1024, so if forward resolution is working, you should not have to modify firewall rules to make reverse work. – Frank Thomas Aug 16 '13 at 19:59
nslookup XX.XX.XX.XX brings back Non-existent domain, I am expecting a host name to resolve. I also tried opening those ports – Gorilla3D Aug 17 '13 at 15:10
up vote 1 down vote accepted

There is nothing you need to allow specifically for reverse lookup (it is just normal DNS via UDP 53), but most likely you are facing the problem that your mail server is not accepted by other mail servers because of lacking reverse DNS. Especially, this has nothing to do with your internal DNS, but rather with the "official" internet DNS. It is sometimes confusing for beginners whom to ask for remedy, but it is logical after all:

When you buy a domain at some registrar, you also register a few DNS servers that are authoritative for the zone (or possibly the registrars servers are used by default). So to make changes to the zone you have to modify the data at these name servers (or have your registrar change it).

The reverse DNS is not related to, so not handled by the registrar. Instead, the corresponding sub-zone of is delegated to the one providing you with ip addresses, that is your access provider. You'll have to contact them to configure the corresponding rDNS entries (or, in case you have a rather large subnet, have the zone delegated to name servers under your immediate control, but you won't want that).

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Thanks looks like I have two options: 1) Contact my ip address provider and ask them to do the reverse lookup 2) Contact my ip address provider and ask them to delegate the reverse lookup to another DNS. I did contact my domain provider and they did not support it. – Gorilla3D Aug 20 '13 at 10:25

You need to put a reverse lookup record into your DNS server so that your mail server's FQDN name can be found by IP.

More info: Reverse DNS lookup

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