Reverse lookup problem

Hello,

Our mail server uses "sendmail" and DNS server used "bind".

We have a problem with sending mail to a site X which returns error
"Sender IP must resolve". So, that means their mail server could not
reverse map our mail server's IP address to fully qualified domain name.

On our DNS server, I can correctly reverse map our mail server's IP
address:
dig -x

The answer section returned is correct.

However, on an external network,
dig -x
does NOT return an an answer section.

Instead, it only returns an AUTHORITY section stating our service
provider's IP address?

Does this mean our service provider doesn't have a "glue record". Or is it
possible "dig" is not sufficient to test reverse lookup and the problem is
at our end ?

Grateful for any help.

Thanks,
Tony
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Re: Reverse lookup problem

Tony Gogoi said:
>
> Hello,
>
> Our mail server uses "sendmail" and DNS server used "bind".
>
> We have a problem with sending mail to a site X which returns error
> "Sender IP must resolve". So, that means their mail server could not
> reverse map our mail server's IP address to fully qualified domain name.
>

As long as there is a reverse lookup it should be OK. Try 'host IP' to
see if you have a reverse lookup, if not, ask your ISP to add one.
Doesn't even have to resolve to your domain name, just as long as it
resolves.

--
Scott

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Re: Reverse lookup problem

Hi Scott,

>
> As long as there is a reverse lookup it should be OK.

But then, the "dig" query does not return the mail server name. Only
mentions the authority is our network provider.

> Try 'host IP' to
> see if you have a reverse lookup, if not, ask your ISP to add one.
> Doesn't even have to resolve to your domain name, just as long as it
> resolves.

>
"host ip" returns
Host ip. not found: 3(NX DOMAIN)


Thanks,
Tony

> --
> Scott
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Re: Reverse lookup problem

The problem is, his internal name server is NOT his public name server.
That is why he can dig internally, but externally he can't.

Tony, to answer your question, yes, the problem is your ISP needs to have a
PTR record setup for your mail server.
----- Original Message -----
From: "Scott Taylor"
To:
Sent: Tuesday, August 03, 2004 12:22 PM
Subject: Re: Reverse lookup problem


>
> Tony Gogoi said:
> >
> > Hello,
> >
> > Our mail server uses "sendmail" and DNS server used "bind".
> >
> > We have a problem with sending mail to a site X which returns error
> > "Sender IP must resolve". So, that means their mail server could not
> > reverse map our mail server's IP address to fully qualified domain name.
> >
>
> As long as there is a reverse lookup it should be OK. Try 'host IP' to
> see if you have a reverse lookup, if not, ask your ISP to add one.
> Doesn't even have to resolve to your domain name, just as long as it
> resolves.
>
> --
> Scott
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html

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Re: Reverse lookup problem

On Tue, 3 Aug 2004, Adam Lang wrote:

>
> Tony, to answer your question, yes, the problem is your ISP needs to have a
> PTR record setup for your mail server.


You mean, our ISP needs to have a PTR record setup for our DNS server
(rather than our mail sevrer) right ?

From an external network,

dig

correctly prints the IP address of our mail server and correctly prints
the DNS server names in the authority section from an external network.

Its

dig-x

on an external network which is the problem.

Thanks,
Tony
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Re: Reverse lookup problem

Tony Gogoi said:
> On Tue, 3 Aug 2004, Adam Lang wrote:
>
>>
>> Tony, to answer your question, yes, the problem is your ISP needs to
>> have a
>> PTR record setup for your mail server.
>
>
> You mean, our ISP needs to have a PTR record setup for our DNS server
> (rather than our mail sevrer) right ?

If you have static IP addresses ask your ISP to put in a reverse DNS for
all and any, that will fix your problem with mail servers not accepting
your email. I Don't see what it has to do with your internal DNS. Your
ISP owns your Internet IP addresses so your ISP must do reverse DNS for
you. You can do DNS for your web and mail servers, but only name to IP
not reverse (IP to name).


>>From an external network,
>
> dig
>
> correctly prints the IP address of our mail server and correctly prints
> the DNS server names in the authority section from an external network.

Of course it does, that is forward, not reverse, which you need. Forget
dig, just ask your ISP for the PTR record, as Adam and I both suggested,
and everything will majically work.

--
Scott

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