Mailing List Archive: How to stop reverse DNS lookup?

How to stop reverse DNS lookup?

chris at dfwstangs

Jun 28, 2002, 6:20 AM

Post #1 of 6 (857 views)

This is a multi-part message in MIME format.
--
[ Picked text/plain from multipart/alternative ]
Hello,

I am running an Exim server for many different domains and client IP addresses.
I am using Pop before Smtp auth with a MySQL database, which is working fine.

The only problem is when the clients try to send an email and their machine IP address does not have a DNS Host name associated with it, due to either a misconfiguration or its deliberate. They get the error "Failed to find host name from IP address".

I have host_lookup commented out. The client IP address is in my host_accept_relay list, but it still tries to find the host name.
The only workaround I have found so far is to put a bogus entry in my /etc/hosts file for the clients IP address.

How can I stop Exim from trying to find the host name for a given IP address? I've searched throught the manuals and FAQ and could not find this particular problem.

Thanks
Chris

--

Re: How to stop reverse DNS lookup? [ In reply to ]

Jun 28, 2002, 7:49 AM

Post #2 of 6 (843 views)

On Fri, 28 Jun 2002, Chris Douglas wrote:

> I have host_lookup commented out. The client IP address is in my host_accept_relay list, but it still tries to find the host name.
> The only workaround I have found so far is to put a bogus entry in my /etc/hosts file for the clients IP address.
>
> How can I stop Exim from trying to find the host name for a given IP address? I've searched throught the manuals and FAQ and could not find this particular problem.

I'm surprised you didn't find this. It comes up with monotonous
regularity on the list.

See sections 10.10 and 10.11 in the Exim 4 manual.

Chances are you've got some host list with a wild card pattern in it.

--
Philip Hazel University of Cambridge Computing Service,
ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.

Re: How to stop reverse DNS lookup? [ In reply to ]

chris at dfwstangs

Jun 28, 2002, 8:00 AM

Post #3 of 6 (884 views)

Should have stated I am using Exim 3.35. I am using vmail-sql and it does
not support Exim 4 yet.

My host_accept_relay list is all IP's, no names.

Thanks
Chris

> On Fri, 28 Jun 2002, Chris Douglas wrote:
>
> > I have host_lookup commented out. The client IP address is in my
host_accept_relay list, but it still tries to find the host name.
> > The only workaround I have found so far is to put a bogus entry in my
/etc/hosts file for the clients IP address.
> >
> > How can I stop Exim from trying to find the host name for a given IP
address? I've searched throught the manuals and FAQ and could not find this
particular problem.
>
> I'm surprised you didn't find this. It comes up with monotonous
> regularity on the list.
>
> See sections 10.10 and 10.11 in the Exim 4 manual.
>
> Chances are you've got some host list with a wild card pattern in it.
>
>
> --
> Philip Hazel University of Cambridge Computing Service,
> ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.
>
>

Re: How to stop reverse DNS lookup? [ In reply to ]

Jun 28, 2002, 8:21 AM

Post #4 of 6 (851 views)

On Fri, 28 Jun 2002, Chris Douglas wrote:

> Should have stated I am using Exim 3.35. I am using vmail-sql and it does
> not support Exim 4 yet.

The general comments are relevant to both 3 and 4.

> My host_accept_relay list is all IP's, no names.

But are there any other host lists? The way to debug this is to use the
-bh option to simulate an incoming connection. That will show when, and
hopefully why, the lookup is happening.

--
Philip Hazel University of Cambridge Computing Service,
ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.

Re: How to stop reverse DNS lookup? [ In reply to ]

chris at dfwstangs

Jun 28, 2002, 8:50 AM

Post #5 of 6 (848 views)

Thanks Philip. I found it in section 10.9 of the 4.0 specs, I needed to
add net- to my MySQL query to get the list for the host_accept_relay option
since I am storing the IP of the clients and not their dns names.

I'll know now to look in the Exim4 specs as well as the 3 specs for problems
since the 4.0 specs seem more complete.

-Chris

> On Fri, 28 Jun 2002, Chris Douglas wrote:
>
> > Should have stated I am using Exim 3.35. I am using vmail-sql and it
does
> > not support Exim 4 yet.
>
> The general comments are relevant to both 3 and 4.
>
> > My host_accept_relay list is all IP's, no names.
>
> But are there any other host lists? The way to debug this is to use the
> -bh option to simulate an incoming connection. That will show when, and
> hopefully why, the lookup is happening.
>
>
> --
> Philip Hazel University of Cambridge Computing Service,
> ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.
>
>
> --
>
> ## List details at http://www.exim.org/mailman/listinfo/exim-users Exim
details at http://www.exim.org/ ##
>
>

Re: How to stop reverse DNS lookup? [ In reply to ]

Jun 28, 2002, 8:58 AM

Post #6 of 6 (848 views)

On Fri, 28 Jun 2002, Chris Douglas wrote:

> Thanks Philip. I found it in section 10.9 of the 4.0 specs, I needed to
> add net- to my MySQL query to get the list for the host_accept_relay option
> since I am storing the IP of the clients and not their dns names.

If only you had quoted your actual setting... :-)

> I'll know now to look in the Exim4 specs as well as the 3 specs for problems
> since the 4.0 specs seem more complete.

The spec evolves, but I don't retrofit.

--
Philip Hazel University of Cambridge Computing Service,
ph10@cus.cam.ac.uk Cambridge, England. Phone: +44 1223 334714.