Re: [Exim] Reverse DNS Lookups

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Author: Philip Hazel
Date:  
To: Terry Shows
CC: exim-users
Subject: Re: [Exim] Reverse DNS Lookups
On Fri, 22 Mar 2002, Terry Shows wrote:

> I guess this is a feature request.
>
> Currently, if you use domain names in host_reject, sender_unqualified_hosts,


host_reject is an Exim 3 option. I assume you are talking about Exim 3.
I'm afraid that feature requests for Exim 3 are closed.

However, reverse lookups do still happen in Exim 4. :-)

> I understand that if you don't use any domain names in your host tables,
> then the reverse dns lookup can be turned off easily, but in my case, I want
> to be able to include some wildcard host entries in some of my tables.


I don't understand what you want. You have something like *.x.y.z in a
host list, but you want to say "if the IP address is 1.2.3.4, don't
look it up in order to see if the host matches *.x.y.z". Is that right?
If so, what do you want to happen? Should 1.2.3.4 be "in" the list, or
"not in" the list?

You can, of course, configure whether it is in or out by putting the IP
address in the list. But you want to avoid doing this in lots of
places... but you may want it to be in some lists and not in others, so
I can't see that any kind of global request is going to help.

In Exim 4, all this control is done in a different way, in access
control lists. It is often possible to avoid listing things more than
once, but it does of course depend on exactly what you are trying to
achieve.

Also note that the "reverse lookup" in fact uses gethostbyname(), so you
can, if you want, put these addresses into /etc/hosts, and get round the
problem that way.

I think I am asking: What is the *real* problem? :-)



--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.